Simon Malik

Again, I question why concrete should be seen as vile, but I also question why it shouldn't be used with other more natural materials. To complement their properties.

Chris Kott wrote:
"Something that lasts only 50 years without maintenance, and only 100 years with constant maintenance, doesn't qualify as permanent in my books. The remains of Roman projects are many times that old. "

I think the thing is though normal, plain gray, Portland cement based concrete actually doesn't have to only last 50 - 100 years. Done well the stuff can last longer than the Roman projects. Brown sugar as a set retarder to gain greater strength, wood ash  and crushed brick aggregate as Pozzolans, thsi stuff can be dirt cheap (no pun intended) and strength concrete. Rufus points to the body of knowledge. Most really bad concrete was done in an era with much, much, less awareness of the issues that can affect concrete. Every decade the amount of knowledge on how to produce durable concrete goes up.

We collectively know far more now than we did in 2009, or 1999. But the concrete of the 90s and late 80s was far more sophisticated than the concrete of the 40s and 50s. And even back then, people knew things that - were it not for short changing price concerns, laziness, or limited information availability, could have massively extended concrete's life back then. The US Government was doing experiments with blending old fashioned natural Rosendale cement with Portland cement to make far more durable highway concrete, for example. Market pressures drove natural cements out of business. Only now, with niche restoration and natural building markets, is the stuff coming back - but horrendously expensive. A broader market, better distribution, and more acceptance of natural cement as a durability enhancing additive to Portland cement concrete - or an alternative for people who want to do concrete with lower embodied energy ( outside of transportation....) could help increase knowledge of it. In Europe there seems to be a far more active, and well moneyed, market for natural hydraulic limes and cements. Much of it, I think, is because of heritage architecture needs. If only this could increasingly translate over to the USA, and in ways more affordable to DIY less affluent builders ...

There are a lot of commonly available, well known in niche markets, concrete additives - some quite natural - that easily produce concrete far more durable than anything the Romans were capable of. In fact, we could produce Roman style concrete, using their ingredients, that outdo what they were capable of. Using their own stuff, because we have better structural and material knowledge.

I think normal concrete, which when done well can last a thousand years, can complement other alternative techniques like cob, rammed earth, unfired adobe, or low fired burnt mud bricks - if the costs of experimenting and and architects, engineers, building code divisions inspectors were informed, aware, and interested and in more conversation with natural builders. And if natural building communities continue to not only share ideas and perspectives - like everyone is doing here - but were capable of more aggressive advocacy and - of course - had more money to play with Natural or alternative building enthusiasts, and Permaculture enthusiasts, all need more aggressive lobbyists and public outreach.

But I feel as if people should be more friendly to, and willing to consider the potential benefits of, ordinary gray concrete. The stuff isn't so bad. It just wants someone to use it in better ways.

C. Letellier wrote: "Personally I consider concrete a good thing if it is well used.  If used properly it is my belief it extends the lives of things like homes or reduces the labor or other energy costs.  Things I expect to change, low use etc should not be made out of concrete but long life things or high use things most certainly concrete should be at least considered.  I will disagree with the homes having a life expectancy of 30 to 50 years statement."

I agree. The thing with homes is that modern American homes are actually build with life expectancies of 20 - 30 years (and only in rare cases 50). Most so-called 'custom' tract homes have life expectancies of 30 years tops. Quality on stick framed US houses has steadily declined from the late 70s/early 80s on. It's planned obsolescence, and contemporary builders alone aren't be be blamed - this is somewhat market driven as well.

There are custom home builders, increasingly, who are doing higher quality work. They are in a minority. Kids born in the average built to minimal code requirements McMansion will see their family home start falling apart at the seams when they are in their 30s to early 40s, and their parents in their 50s to 60s.

I think if someone is building something to last a long time, with minimal maintenance, normal concrete done properly - just like properly done bearing masonry - can last centuries.

Rufus Laggren wrote:
"Concrete alternatives are not any stronger than concrete and they don't last any longer, right? So no structural or functional advantage there...
Concrete done incorrectly doesn't turn out well, but that is true of any process and concrete has a huge body of knowledge and installed base that all can reference, That means concrete work has a significantly better chance of turning out right

I agree, but I believe the concrete alternatives actually are forms of concrete anyway, there are semantics, perceptions, definitions - I think that just because modern reinforced concrete has this huge body of knowledge doesn't mean that we shouldn't explore other alternatives. For example, rammed earth or lime based concretes are vapour breathable, a solidly concrete house needs careful attention to ventilation because it;s essentially airtight, especially with energy efficient windows and doors. Many modalities of commercial green architecture see airtight structures as a good thing. But there are trade-offs. Lime based concrete, or lime reinforced rammed earth, is more vapour permeable. This can lead to fewer problems with condensation and damp. Of course done properly, with detail paid to ventilation, you could pour a monolithic concrete box and dome and minimize condensation problems. That comes in the design.

There are contexts in which Portland cement is more expensive than other alternatives. Not in Europe and North America, but there are huge areas in which Portland cement is extremely dear. Better understanding of lime concretes, ir clay and earth alternatives, existing vernacular uses of rammed earth, etc., can open up natural, healthy, beautiful homes to people who wouldn't be able to afford properly done and detailed reinforced concrete homes.

Portland cement based reinforced concrete can, and should anyway, play a role in alternatives. Seismicity is a huge issue in many parts of the world. Someone interested in more natural building could use earth based types of masonry and, for example, do monolithic concrete bond beams, plinth ground beams, reinforcing columns, foundations to overcome seismic issues.

Heck, in North America, where cement is cheaper and yards of readymix are more affordable, concrete is still astonishingly expensive. So too is the engineering needed to spec out slabs, walls, etc. Especially for a DIY builder. Market pressures (including house and real estate valuations, the mortgage and lending market, a huge commercial market able to pay top penny for skilled contractors) all push up the costs of concrete. So too, permitting. In my wife's country everything is done in concrete. Stick building would be both extremely expensive and extremely undesirable. The idea of building with wood is seen as insane. So the market responds, wood - in a Mediterranean country with large forests - would be a niche luxury accent material. Panelling, and just raw scaffolding and formwork material. Concrete is expected for structural work, and is priced in a way that home builders, even families building incrementally, can easily afford it. In other countries concrete is more expensive. Markets dictate a lot. Every place has different needs.

I think all of this stuff can complement each other. Concrete and Concrete alternatives. Hempcrete, or sawdustcrete, for example, has insualtive properties as well as mild compressive strength. Earthcrete may be a good way of diverting waste earth fill, and get something useful out of it.

There's more than one way to peel a pear. If someone wants to actually peel pears, anyway. There's also more than one way to peel an orange. Oranges and pears, though dissimilar fruit, can be really tasty together in a fruit salad.

I think masonry (especially structural bearing masonry), ordinary concrete, and earth based monolithic masonries (cob, rammed earth - which are all types of natural concrete anyway), lime based masonries and concretes, and other alternatives can all work together - in the mind of an imaginative knowledgable architect or builder - to make healthy, more natural, and very long lasting homes. And I don't see why they shouldn't work together..

Howdy everyone.

Just some thoughts, to riff off all of the amazing answers above (mentioning everything from cover concrete, to the use of alternate reinforcement). I think that Part of the problem we face lies in definitions and perceptions. So too, many more ecologically harmful aspects of contemporary reinforced concrete (not mass concrete) lie in contemporary construction industry practices, with the need for timetables, efficiency, and compliance with certain code and engineering mandates. Which are largely based on how concrete is being used (as tensile stress bearing structural elements, for example). All of this influences how we often see concrete and Portland cement. But perhaps it need not be this way.

I think that looking at concrete's past with a broader view of what it really is, and expanding conversation and information/idea exchange with engineers, natural builders, architects, code enforcers, will all help create a broader conversation in which concretes, be then clay based (seeing Cob as a type of concrete, for example) or lime based, or portland cement based, are seen more broadly as different approaches and tools more suited in some cases, or others.

In fact, modern concrete evolved out of the use of rammed earth, through Tabby. Which is from the Arabic Tabiyya, through Spanish and Portuguese Tapia or Tabia. Military or Royal Tapia is lime stabilized, a technique from the North African Maghreb. It's lime stabilized rammed earth. It is, in fact, a form of concrete. Just as ancient Roman concrete was based on a lime, mixed with various kinds of earth (not only volcanic Pozzolana. The Romans used many kinds of sands and earths in their concrete composition) and rammed in wood forms, with layers of stone aggregate (Caementum, whence we get the word cement from). But concrete itself is pre-Roman however. The Carthaginians and other North African civilizations used forms of lime based concrete in Punic cities, as well as rammed earth, centuries before the Romans started using the technique. It's likely the Romans learned about lime mortar, much less than concrete, from their interactions with Phoenician/Punic cultures and the Greeks. The persistence of the technique mainly in North Africa and Iberia, long after it died out in the other Roman areas, is a clue to this.

Spanish uses of Tapia/Tabia in colonial Mexico Florida, Texas etc. as well as the familiarity of some African slaves who used it indigenously in their own cultural contexts, led to the adoption of rammed Tabby, in the American South and East Coast. It was a sea shell based lime concrete. "Tabby" eventually evolved into "Gravel wall" construction. Interest in concrete "gravel wall" construction increased as interest in Pise/rammed earth in France was exported to America and England, and interest in natural, and then artificial, hydraulic cements increased. A few years ago someone on this forum (I cannot recall who) very kindly directed by attention to the early history of French Beton. Well, French Beton (concrete) evolved out of the tradition of pise - rammed earth. All of these influences, between North Africa, Southern Latin Europe, Latin America, England, and North America, all internationally came together in the 19th century as literature and travel enabled the exchange of ideas on these matters. French, English, and American concrete technique and material eventually evolved, each country influencing each other. There are really interesting the webs of influence, from France to England to America to France and England, back and forth, as invention and technique increasingly refined what we know as modern concrete evolved.

All that Concrete is is simply a binder with aggregates. If Portland cement is the binder then clay or silty earth is an aggregate just like sand, or ground pumice, or ground recycled glass. Or sawdust. These are all concrete, full stop. In modern building codes and textbooks concrete is defined as Portland cement with aggregates, be they sand, gravel, crushed stone, or other aggregates.  But in reality concrete is any binder - be it clay, lime, gypsum, or Portland cement (or natural cements) with aggregate - be it sand and gravel, or boulders (so-called plum concrete)

In this sense, Cement stabilized rammed earth IS concrete anyway. Even non-stabalized rammed earth is essentially concrete. So too with Earthcrete, it's just concrete with dirt as the aggregate. Hempcrete IS concrete. It's concrete with shredded hemp as the aggregate (and either lime, or Portland cement, as the binder). How we look at the thing influences how we vile we see it. Concrete is a really broad modality that can encompass many types of materials.  Technically asphalt is even a kind of concrete. The binder is tar, but we don't want that....

Rez Zircon wrote:A minor point about expanded metal lath -- it can disrupt or block wireless signals.
I once lived in a house with metal lath and plaster walls... had to stand in front of the window to use the cellphone.

Hi Rez,
Thanks for the kind words earlier. Your sister's house sounds really cool. Her floors sound beautiful, it would be really interesting to know what she used.

That's a good point on expanded metal lath. I work in an older building with tons of plaster on metal lath and the stuff is not kind at all to wireless signals. This could be very good for people sensitive to higher frequency wireless.. but it can be a real bummer in turns of today's living, mobile, wifi, the works...

Something just popped in my mind. If for any reason someone wants a space in which Wireless signals are deliberately blocked I wonder if this could be a good side use of expanded metal lath.

Let's say, if you can get a good quantity cheaply enough, you could just affix it to the studs and floor boards of a room, and re-plaster it all. Just attach self furring lath to all walls, floors, ceiling, and connect the seams with some conductive wire, and once it's all solidly plastered over you would have a room that's relatively interference free.

That is just a random thought that popped in my head. I haven't done this.. but I'm tempted to plaster a closet up like this for giggles, and see how much signal it blocks.

Some hardware store chains have self furring expanded metal lath for around or under $8 for a 2'x8' sheet.  Since it's self furring you can put it on just about any surface and plaster over it. The stuff is designed to give a solid substrate for plaster. Put a scratch coat on, then a brown coat, then a finishing coat. Then paint using a low vapor emission, or natural paint. Or use mineral pigments and lime and whitewash paint it. Or even tile all over.

In many parts of North Africa, Spain, and Portugal some people often partially or fully tile entire walls and floors. Especially in living rooms or salons. I saw a lot of this in Morocco and Algeria. I think it can be a rather pretty, and practical from a cleaning perspective.  I've seen very chic and modern looking ceramic tile panel modules, especially 3d designed ones, attractively tiled from floor to ceiling in upscale homes. Plastered self furring metal lath is a great substrate for tiles (it's how bathroom walls were tiled before cement backer-board was invented) so you could make a signal blocked room, nicely and attractively tiled up.

Just random thoughts and ideas, Cheers everyone.

So a bit more. The thing about lime plaster floors is they need time to cure, but are more crack resistant - yet softer and weaker - than concrete floors. Gypsum plaster is even weaker and softer. Let both types of floors over time can cure to almost stone light hardness, and examples exist that are hundreds of years old. Some in old houses are accidentally mistaken for more recent concrete floors.

To visualize the process I dug around on the web for pictures illustrating the process of line-ash and plaster floors. These ones I found online may be helpful:

Here is a good illustration from the web of how to lay down a traditional lime-ash plaster floor. Sometimes a picture is worth 5000 words !
https://live.staticflickr.com/4104/4975092504_db876aabed_b.jpg

Here is good article about lime-ash flooring:
http://izreal.eu/2014/07/20/lime-ash-flooring/

Here are more random pics
A modern limecrete screed, over underfloor radiant heating tubes:
https://www.oakridgecornwall.co.uk/wp-content/uploads/2015/07/Limecrete-screed-over-underfloor-heating-cornwall.jpg

Someone in the UK laying a modern limecrete floor
http://www.greenspec.co.uk/images/web/materials/limemortar/limcrete-floor-2a.jpg
after
http://www.greenspec.co.uk/images/web/materials/limemortar/limcrete-floor-4a.jpg

Screeding a new lime ash floor for Tattershal Castle, in the UK (source with interesting pics) https://www.wheathills.com/product/tattershall-castle-floors
https://www.wheathills.com/uploads/images/IMG_0879-resized.jpg

Float-finishing the caste's restored floor
https://www.wheathills.com/uploads/images/WH2-resized.jpg

Floor under-boards and bits of straw, from a plaster floor restoration job (source http://oldhouserepairs.co.uk/id69.html)
http://oldhouserepairs.co.uk/sitebuildercontent/sitebuilderpictures/LimeAshPrep2.JPG

Same floor
http://oldhouserepairs.co.uk/sitebuildercontent/sitebuilderpictures/LimeAshPrep1.JPG

After Restoration
http://oldhouserepairs.co.uk/sitebuildercontent/sitebuilderpictures/LAFinal.JPG

View of the laths on the underside:
http://files.websitebuilder.prositehosting.co.uk/fasthosts14425/image/underlimeash_1.jpg

The underside of a modern restored lime-ash floor
https://pbs.twimg.com/media/As700u8CIAE89cU.jpg

Underside of a historic lime-ash floor:
http://izreal.eu/2014/07/20/lime-ash-flooring/lime-ash-floor-01/

Close-up of a modern lime-ash plaster floor reed mat shuttering, with a base coat of lime putty, nailed down by wood strips (from the source link listed above)
http://izreal.eu/2014/07/20/lime-ash-flooring/lime-ash-floor-01/

The above with the main layer of plaster being put down
http://izreal.eu/wp-content/uploads/2014/07/Lime-Ash-Floor-03.png

To imagine actually doing this, think about the technique of the old fashioned American and English thickset bathroom floor mud pans. The old Parisian plaster floor was not too different. A thick slab of bedding mortar was laid down enclosing the floor joists. Several inches down coping boards were nailed on rails, nailed to the joists themselves, to keep the mortar from falling below. These boards acted as formwork/shuttering. In the late 19th and early 20th century sometimes joists were shaved to a point at the tip, to help the mudset mortar slab to better get a key. Modern codes would probably frown on this because you have direct contact with the joists, which are structural members.  Later in the century metal lath was put on top of floor boards and the thickset mortar applied.

This pic sows an example of thick-set between floor joists (Source https://www.thisoldhouse.com/ask-toh/mysterious-subfloor ) - it's actually more common than people think, under their feet in old houses)
https://www.thisoldhouse.com/sites/default/files/styles/banner_3/public/migrated/tout-images/subfloor-x.jpg?itok=XaSjE2LH×tamp=1464295937

Another example:
https://www.diychatroom.com/attachments/f5/384513d1495582986-1950s-thickset-mortar-bed-img_8676.jpg

Nowadays thickset floor-bedding mortar 'mud pans' are laid on top of the subfloor, usually  with a vapor/moisture membrane beneath, like tar paper or plastic sheeting.

A modern example:
https://diy.sndimg.com/content/dam/images/diy/fullset/2008/1/28/0/dbtr502_3fd.jpg.rend.hgtvcom.1280.960.suffix/1420606006661.jpeg

Bathroom floor gypcrete over wood in a 1980s condo
https://www.contractortalk.com/attachments/f3/64141d1327640293t-should-i-put-membrane-between-concrete-topping-over-plywood-subfloor-100_8942.jpg

Modern mudset laying for shower pans, from Sakrete
https://www.sakrete.com/blog/creating-a-mortar-bed-for-a-shower-installation-using-sakrete-sand-mix

A modern lime concrete pour, over membranes, in an older rennovated house
http://timberandlime.com/wp-content/uploads/Pouring-the-Lime-Concrete-over-the-LECA.jpg


Traditional plaster flooring is breathable however which helps prevent rotting wood joists because moisture has a chance to evaporate, and isn't trapped. This is the real reason codes frown upon concrete directly touching structural wood. Modern concrete is impermeable. Moisture cannot evaporate and is trapped. The traditional methods lasted centuries.

In this case, unlike with plaster floors, the mortar was usually at a dry pack consistency, similar to a rammed earth mix or really damp sand on a beach. Good sand castle making consistency.. It would be barely damp, stiff, like zero slump concrete. You would be able to make squeeze a ball in your hand, and it should hold its form, like a well squeezed ball of damp sand or clay. This stuff is dumped in place, troweled floated and compacted. It was sometimes rammed.  The advantage of the old way is that the joists were literally embedded, so you wouldn't risk delamination.

Now in any case you could want to consider something similar, by adapting the essence of the older techniques to a modern context. So let's say you are going to do lime ash instead of cement based mortar. Since you are doing this over an actual floor you could, for example, nail or screw down modern expanded metal lath as a substrate, or nail down strips of wood laths. You could also look into how modern gypcrete is laid over plywood subfloors for ideas. Modern gypcrete and concrete flooring tends to be directly applied on the wood floor or sub-floor, or on top a plastic membrane. There is a lot of documentation on laying and finishing gypcrete.

As to the mortar, there are historical lime-ash recipes floating around. You could look up what was historically done, and look up what modern restorationists are doing. You have lime – depending on your budget there’s Type S masonry lime, or more expensive specialty NHL (Natural Hydraulic Lime) or AHL (artificial Hydraulic Lime) that’s being manufacture red. For ash, you could probably, for example, use well burned barbecue grill ashes, or a wood bonfire ash, well sifted through a screen. Maybe gather barbeque grill ashes from local picnic groves and parks, add to your own from when you cook out. Save it in a small plastic garbage can.

Also if you have a barbecue grill and no neighbors to complain nearby you could probably calcine autumn raked up leaves and dry grass clippings in patches.  (Avoid burning poison ivy by mistake :-) Leaves have a lot of silica. Leaf ash can be more reactive with lime mortar/plaster when mixed in. Some people say that twice burned ash is even more reactive, or at least I've heard people say this. Sift the ashes into a bucket placed over a tarp, normal screen window screen mesh would get large un-burned twigs, etc. Chunks of 4th of July barbecue grill nasties, etc., out of your ash.

You could also use ground up brick dust (which is middle eastern 'horasan mortar') it turns into a natural lime based concrete but is more crack resistant. In some areas you can source ground up brick from landscape supply companies. Another idea - hit up local ceramics shops, ask for their cast offs, place in thick sacks, whack with sledge hammers until you pound it into aggregate. Ceramic waste (brick, pottery, crockery, etc.) when ground up/pounded has pozzolanic properties. This means it gives lime a hydraulic set, makes it stringer, more like concrete. Modern masonry lime is not very reactive at all. Reactive lime is very expensive, because it's used for niche high-end historical restoration people. Adding ground brick aggregate to wood ashes makes the mix more reactive. It could have a harder and faster set and cure.

To increase the crack resistance and give more flexural strength to any plaster rendering traditionally people could add fiber, usually animal hair. Traditionally horse hair was favored by plasterers. Modern plasterers also sometimes use artificial poly fibers. However well washed human hair is very strong, and there’s some experimental uses of human hair as mortar and plaster fiber. You cut tresses into shorter segments with scissors. You can literally just go to a barber, ask them for a bunch of their hair shavings. Wash them very well with detergent or some degreasing soap. Just 'shampoo' bunches of hair in a plastic rubber maid bus-tub in your bathroom, rinse well, let dry very well, then cut into more manageable lengths and mix into your plaster/mortar mix. There is a lot of historical info on plastering with hair, etc.

A modern way would be just embedding nylon mesh or fiberglass mesh in the mortar pan, to give it flexural strength.

If you have time and good weather on your hands here is a good way to test out mixes. Take a few wood pallet skids, and penny-nail down small wood lathes with small gaps across the pallets slats (some Home Depots still sell wood lathe in bundles for plasterers). With others use expanded metal lath, if you have access to it and if it’s affordable. These are going to be your mini test floors. You would come up with different experimental mixes, and plaster trowel a 2" thick layer across the whole pallet, level it and float it, and ignore your neighbors' curious looks. Wood float finish it smooth, and let it further set and cure. You can and walk over them, drop hammers, jump, get neighboring parents permission to allow their kids to jump up and down, etc. See how the mix handles to flexing, impact, and use. See how it cracks during curing, etc. When you are done break the test mini-floor sections up, and just re-use the chunks as aggregate after hammering them into smaller rubble...

Next, instead of lime you can do gypsum plaster of paris flooring. Gypsum plaster’s direct modern equivalent is "Gypcrete” flooring, which is becoming popular in some high end hotel and condo builds around the country). What you have is just a thickset pan made of a plaster of paris based mortar. There are different formulas for mixing the mortar, in various ratios, as with lime-ash. Other substances are needed as aggregate, from sand to crushed bricks, and traditionally people also sometimes mixed in clay earth, loamy earth, silt, broken pottery and crockery, and other substances. It was never straight plaster. You also would need retarders, because all gypsum plaster sets quickly. Traditional retarders ranged, including lime putty for example slightly retards the setting. You have to prevent the gypsum plaster from setting up too quickly to be worked. Tri-sodium citrate is a modern retarder, there are others. Today, some markets have high quality finishing plasters that have a slower set and give a harder surface.

If you read up on these various techniques you should be able to figure out a method that works best to your unique situation. In old libraries, Google Books, and archive.org, pdf docs from restoration societies and government heritage sites, you may be able to find a wealth of information to shed light into whether this approach would work for you.
Good luck !

Hi ! Here are some ideas that I hope are useful. Riffing off Travis's idea on a concrete floor (I love concrete floors!) what you would be considering is a floor screed that’s similar to an old fashioned thickset mud pan of bedding mortar, as used in old Victorian or Edwardian bathrooms as a base for floor tiles. Anyone who has rehabbed really old houses has probably run into these.  You can get creative ideas on different ways of doing this, variants on the technique, by looking up older builder/construction material on laying tile on substrates of bedding mortar pans. Now, the thing is many people do not like Portland cement, see it as artificial and unnatural, having high embodied energy and ecological costs. But you can do the same thing without Portland cement. If you want something more natural then there are historically used and proven alternative ways using Lime and/or Gypsum Plaster of Paris.

You would want to lookup "plaster floors." There is a very long history of what are variously called "lime ash floors",  or "gypsum floors", or "alabaster floors", or "plaster floors", or gypsum plaster floors,. etc. There are many documented archaic mixes, some combine clayish earth with the lime or gypsum.
They used to be very, very, common in England and France. They were used in earlier periods in Southern Spain/Andalusia. Through North Africa from Morocco all the way east similar practices were done, using thick mud slab of clayish earth floors over wood floors comprised of timber joists and beams, with reed or grass matting as bedding, in which a large amount of lime or gypsum was worked into the earth. Terrace roofs in the region were done in the same way, and variants of the practice can be found mostly through the Mediterranean basin on Europe Africa and the Middle East, but in Europe mainly only in England and France. I suspect the technique was an import into the West from the crusades, since they only seem to start appearing in the 1200s.

Traditional English lime ash floors are suspended wood floors comprised of timber joist and beams, with wood laths or reed, cane, or hay matting over which a 1 ½ to 3 inch (rarely thicker) of a pozzolanic lime and wood ash based mortar was laid. This mortar was troweled and wood float worked and polished before curing, and with time became a strong natural concrete floor surface. Lime ash is a mortar and plaster made of reactive burnt lime, sand as aggregate, sometimes crushed brick, and then wood or coal ash. Sometimes eggs or spoiled milk were used in the mxi for different properties, or bull blood. Which is ethnically sketchy in today's world, but if someone has a homestead and slaughters their animals it’s probably better than wasting it. The proteins in the milk or blood added certain properties to the mortar...

Why it works is lime ash is a weekly hydraulic cement. It sets both by drying and carbonation, and forming certain crystalline structures similar to that formed in Portalnd cement. So it’s basically a weak cement. Lime without ash only sets by carbonation, and takes much, much, longer to set. “Roman cement (Opus Cementum) was based on this, using volcanic ash, or crushed brick (Opus Signinum). There is a lot of info on doing lime ash flooring in the UK, it and modern "limecrete" floors are just a version of this idea. They have the attention of lots of historic restoration and natural building folks.
Now, gypsum plaster floors are very similar, but use a mortar or plaster made of plaster of paris, with sand, and other aggregates added. So too eggs, or spoiled milk, etc. were added. The mix is heavily worked before full setting to make a dense and smooth surface. Gypsum plaster floors are weaker than lime ash plaster floors. Sometimes the two were combined, with about a 70% gypsum to 20% lime ash ratio, with the rest being sand, crushed brick or crockery, bits of charcoal and coal dust, animal blood, or dung, or eggs, and other weird Harry Potter kitchen-like ingredients…
They were often finished with linseed oil, or pouring several gallons of bad sour milk over it, mopping it in, and polishing off. Which sounds disgusting smelly. But the result was supposed to look beautiful and stone-like. Sometimes it was finished in a fake tile pattern, like a checkerboard and so on.
I'm sure there are photos for examples on the net, I'll search around and post some.


How it was traditionally done is this:
To make the floor the mortar mix is plastered over an organic bedding, a floor substrate serving as a kind of subflooring and shuttering formwork. Traditionally these wood laths, the same kind of laths used in walls, OR reed/cane or even hay/stray bedding. Lathing gives keying, like something to teeth on. So did the organic bedding, whether cane or hay/dry grass. It also formed a formwork, a shuttering of sorts, to contain the fluid plaster until it dried and hardened. This gave a floor surface that would not easily de-laminate, and would properly cure.

The lathing or bedding that’s nailed over the joists and beams basically takes the role of sub flooring or floorboards. The laths are just nailed across the joists - just as you would see in old fashioned house ceilings - but on the upper side.

You then lay wood guide rails that are as deep as your intended pour. The serve as guides and divide the job into sections. You put down some plank platforms that rest on-top of the rails to kneel on and work off and to walk over already laid sections. The platform keeps you and your bucket and trowel nice and tidy and gives a work platform. Then you pour in your mortar or plaster in the section, trowel it down and roughly work it. Before it fully sets you have to further wood float it for a smoother, denser, more compressed surface. You would follow similar guidelines as found in resources on floating and finishing plaster walls for a smooth surface. You are doing the same thing, just horizontally. The thing is, however, there are no scratch coats, brown coats, etc. It's one coat.

When you finish a section, you move the guide rails over, and do another equal sized section. The advantage of doing it in sections, and not as a monolithic poor is you end up with segments that are jointed, which would prevent cracks in one section from spreading, and it makes the job more manageable. Also plaster sets very quickly, doing it in smaller sections enables you to actually do the job without risking it setting before being worked.

So imagine instead of pouring a huge section, you the mix is troweled over it the cane, reed or straw bedding, or over the wood laths. If used the cane bedding is additionally secured by nailing down running wood strips perpendicular to the direction of the bedding. Sometimes a thin slurry of lime putty was applied to the bedding to better help the plaster key in and attach, and to keep runny plaster from dribbling down below. If the underfloor was to be left as is then the plaster drips would be unsightly. But, if the underfloor was going to be a plastered over ceiling then the upper floor plaster drips could serve as a useful plastering key for the underside. In any case, whatever the substrate or underfloor was, it was generally laid out perpendicular to the actual floor joists directly.

In 19th century Paris, plaster floors were poured directly over the joists, with sort of coping boards lowered between the joists or somehow suspended below the actual the joists. The floor was poured in sections. This was a labor intensive and expensive technique, it used a lot of material but aided fire resistance, because the joists end up being fully embedded in plaster to some depth. It also confined the joists and added to the floor stiffness – and weight.

Traditionally the floors were allowed to cure without traffic for a fortnight to 3 or 4 weeks.

Hamza Rahy wrote:...But, i was wondering about the logistics or using brick to form a dome-like roof (somewhat common in Mexico). However, another aspect is that it would be in a fairly rainy and cloudy place, with lots of wind... Could it be possible? I know i'd probably have to hire out because brick roofs are hard to master (probably wont stop me from trying and failing anyways lol), but was just wondering if it would even be physically possible before i start making the plans.
If that's not possible, would an alternative be to just use cob itself? if you created a good enough lime seal (maybe even tadelakt) and made sure that it had spectacular rain run off, would it hold up or would it simply wind up disintegrating?

Hello Hamza ! Where are you located? Phil had some good links, I'd like to add some pics and a few thoughts. Now, don't let my words discourage you, I wanted to do this also, but the expense and headache disappointed me. I didn't have the resources. Perhaps you would, however.

You are looking at a masonry vault of some sort. And modern governments do not like to approve the building of structural masonry vaulting. The skills died off, and very few people kept doing it, but people today are re-discovering it from a technical, engineering, and practical standpoint. The idea - if in a seismic stable area - is ecologically brilliant in that you aren't cutting down trees. Wood's renewable but cutting down entire forests to build roofs and floors has obvious impacts. However brick, cement, burned lime, all have encological tradeoffs too. But the results have a permanence that can last generations.

You would need to have it engineered to get anything like this approved, and very few modern engineers would ever want to touch brick vaulting. If someone could and did engineer it then they would probably want you to use a lot of rebar.  Also builders today really don't know how to do structural brick vaulting. Now, if you know Mexican builders who know how to do this, then at least you'd be able to hire someone. But if this is done in the USA the labor costs as well as the costs.

If you can find a structural engineer who actually understands vaulting, and is willing to design a vault, and understands the geometry and material and their behavior and trusts it enough not to put 50 tons of steel over your head and a concrete slab just to make it work, then you may be able to get it done. OF course in most places the engineer has to be licensed with the state in order to stamp plans. Maybe you can explain it well enough to an engineer who doesn't specialize in vaults, enough that hes'willing to take a stab at it.. Now, if you have time and financial resources, and if you live in an area where building inspectors would be willing to sign off if its properly engineered, and you have access to an engineer willing to do this, then you could pull it off.

To do so you would want to really, deeply, understand what you would want from an architectural and engineering standpoint, enough to explain it, and direct him or her to other technical resources. Me, I don't have the time, money, or patience. Maybe someday.. ther'es a reason why stick built ceilings are the norm in America though. It's well understood and everyone can build one and the skills needed for builders are much less..

Basically what you want to do is a vault. I've pasted some pictures below to look at. it's physically possible, and sustainable. For tile vaults, Phil's links are great places to start. From there just do more searches on "timbrel vaults" "Guastavino vaults" "tile vaults". In Italy I think they are called Realine vaults (if I recall, something to that effect). Also look up "Catalan Vaulting."

Waterproofing is an issue. You mention tadelakt - that's a labor intensive technique, especially over a whole roof. And you would have to maintain it on a regular basis. Vaults are masonry. Water + Brick + Mortar joints + Freeze/thaw cycles are bad... cracks let water in, and compromises the building. Traditional techniques like tadelakt should be read up on. In modern times when vaults are done (look up French documentation on Nubian vaults in Africa, there's a whole useful How To manual floating around in pdf showing exactly how to design and build a barrel vault ceiling with adobe bricks. The same techniques would apply to any kind of brick) you would want a water proof barrier over the vaulting. Like plastic sheeting, maybe a couple of layers, well taped. There's some pdfs out there on how to do this.. Some architects have used tile vaults as a stay in place form, then poured a concrete slab over it. This has to be done in a balanced way so that excessive weight from the pour doesn't cause collapse of one area. The brilliant thing is that some kinds of vaults grow more stable when under a balanced load. But the load has to be balanced, and point loads in one area avoided..

The main problem is dealing with the thrust, the geometry of the brick vaulted roof is important. The more curved it is the less thrust, or rather the lines of thrust follow the curve of the vault to the ground within the thickness of the wall the ceiling or roof rests on. The flatter the arch, however, the more the thrust spreads out. You need something to buttress the walls. If this is miscalculated or poorly build you end up with tons of bricks falling on your head.

Tile vaults are lighter, so they produce less thrust. That's what allows them to be more easily built freehand, without a form to support the bricks or tiles. But still the walls have to be able to absorb the load generated by the thrust, and carry it safely to the ground and foundation. One trick modern builders do is they pour a reinforced concrete ring beam and they "spring" the vault from a point contained in the beam, that way the beam absorbs much of the thrust, doesn't rupture from the load, and safely transfers it down the load bearing walls down to the foundation.

Back to waterproofing, you mentioned tadelakt and lime: Something you might want to read up is what's traditionally done in the North African Maghreb. In some parts of Morocco lime sealed roofs are still done, mainly in renovation and maintenance of older houses. I don't think it's done at all in Algeria or Tunisia anymore though. I have read about this still being done in Morocco, though. Mainly not in new builds, but rather in repairing older housing stock. Modern builds are mostly done in concrete. Traditionally the roofs are earth slabs, compressed with rollers. Basically Cob over wooden rafters/joists, with a formwork (shuttering) later of branches or leaves. Incidentally exactly how adobe roofs with Vigas are done in the old American south west, and Mexico. (And also the case in other parts of the Arab world, in the middle east).

I have heard this is still done in some rural Berber houses, by the way. So that may be a place to research.. Now, over this compressed earth slab floor/roof you put a lime layer on top. Its basically what people would call limecrete today. A few inches of lime mortar, compressed and worked in and burnished. This consolidates the material, works out air pores, makes it denser. Then some sort of fat, or soap, applied while the lime is hardening but still somewhat plastic, and then worked in. It's similar to tadelakt. Once fully dry and cured it's basically a lime based concrete with a water resistant surface layer bonded to the material. Fats or soaps react to the lime itself making a crust, exactly the stuff that you get on your shower walls over time. Here it's structurally part of the lime surface, and thick. However it needs maintenance. In Yemen there's a similar technique called Qadhat. Both are extremely resilient, crack resistant and more flexible than concrete, but you aren't gonna find anyone nowadays who knows how it's done.

It's extremely labor intensive. That's why no one in that part of the world likes to do it anymore, and the skills needed mostly died off two generations ago. In Morocco the government subsidizes certain building crafts like this, and in Yemen the Agha Khan foundation subsidized them, so a new generation of masons and builders are learning them from the old masters. Also there's demand in Morocco for traditional housing from Western expats. Hopefully that will keep these natural building skills alive...

In today's world you would probably just want to do two thick poly sheets, properly sealed and taped, and do a basic one or two inch limecrete layer over that, or even concrete. Or latex concrete. Or something akin... So enough about water-proofing, what about the roof itself? Well, again, you are doing a brick or a tile vault, as Paul indicated. The two are similar, but there are differences.

Back to tile vaults:
This example, from an old house in Barcelona I think, illustrates the layered composite nature of the vault, the layers overlap, embedded in the mortar, as it cures it becomes almost a monolithic concrete like mass.


Now, you mentioned Mexican style vaults. They are different from timbrel vaults, but the techniques are related in some ways and tile vaults probably evolved out of earlier freehand brick vaulting techniques. Both are usually done freehand without forms, but Mexican vaults "Bovedas" are single brick thickness.







The technique is very similar to what was done in some parts of the Middle East and North Africa. Look at pictures of the "Basilica Cistern" in Istanbul. They were done using a very similar technique as the Mexican ones.

It is a "leaning brick" type of vault, the bricks are porous, the mortar is sticky. If you Google "leaning brick vaulting" or "pitched brick vaulting" you will find lots of information. The technique was common in Sassanian Persia, ancient Egypt, the Romans adopted it but didn't use it much in the Western Empire. The Eastern Romans however used it a lot and it's found all throughout Byzantine era Anatolia. The Ottoman Turks learned it from them and continued the technique through the province of Rum.

A modern examples of the technique:


This is the Cistren in Istanbul I mentioned:




Other Eastern Roman/Byzantine examples
https://static.cambridge.org/resource/id/urn:cambridge.org:id:binary-alt:20180929073907-12263-smallThumb-05935fig4_64.jpg?pub-status=live

An illustration of the technique:




Now, this is still done today, and there's a bit of a revival, in West Africa's Sahel region. Some NGOs have tried to spread the technique of using Adobe or compressed earth brick pitched barrel vaults in Africa, they are calling the technique "Nubian Vaulting."



Cross section:


Back to the Americas, pitched/leaning brick vaulting done Mexican "Boveda" style :
https://i.ytimg.com/vi/PB8TWMKHHMQ/maxresdefault.jpg





If you look close you can see a poured concrete ring beam on top of the wall, from which the vault "springs":


The Auroville project in India has a lot of information and experience in this. You may want to look for their website.
This is one of their vaults:


http://1.bp.blogspot.com/-fXSMpWD_7c0/Tw2K1OiLGaI/AAAAAAAABEU/xa4iZ_vfn70/s1600/8.jpg

About the tile vaults Phil mentioned, there's a professor at MIT who has done a lot of research into them, and did work on getting them accepted once more in the Engineering community. There's lots more interest and projects being done, but the odds of finding someone who knows how to do or design them is low.

An example in New York:


Cob.. wouldn't work, as Phil says. But adobe vaults can and have been done. The odds of getting an engineer or building inspector to approve them is even less though.
Example pics:


One being built in Mexico out of adobe: http://caneloproject.com/pages/mexico/dome.html

There's a builder in Tanzania who blogs about this, he and his building crew have done many of these kinds of vaults and has a LOT of practical knowledge. An engineer designs them, then he builds them. If you can find his blog it's an amazing gold mine of information.

Anyway I hope that gives you some places to research, some inspiration, and that you have the resources to get this engineered and pulled off.

Howdy everyone !
Riffing off what Glenn Herbert said. Traditional houses were not designed for the kind of water intensive lives we now lead. In modern houses the wet areas, baths, kitchens, are inside. Cooking produces an immense amount of water vapor, so does bathing. Not to mention the general water vapor from our respiration.   Traditional houses everywhere had no vapor barrier and were generally built of vapor permeable materials. The thing is, the ways of life in the past were quite different from ours.

Some estimates are that an average family of four releases about 3 gallons of water a day in pure humidity, just vapor. Some lifestyle choices may actually release more.
In the modern world we shower, cook and boil water at home, and the amount of water we sometimes use is prodigious. A fun experiment is put a large plastic tub or bucket in your bath tub or shower stall, aim the shower nozzle at it so that most of the water hits it, and let the shower run for 10 minutes. Take a funnel, and a couple of one gallons milk jugs or pitcher. Pour all of the water into a jug or pitcher until its full, then go empty it on the houseplants or garden. Count the number of times you fill up a jug. We do that every day in taking a bath.

Traditional houses do allow air and water vapor to move freely, there is a thermal cost but people tended to insulate their bodies, wearing more or less layers of clothing. Also space radiant heating was more common. Even in the 20th century, up until recently whole house heating was a middle class or wealthy luxury. Older poorer houses had gas space heaters, or even coal and wood stoves. Up until the 1960s and 70s coal and wood stoves were an economic necessity, not a lifestyle choice, for millions of Americans. People "bundled up" in the winter. In the summer they opened windows and doors, which encouraged air circulation. Poor thermal performance, even in an age not concerned with the ecological impacts of our energy use, was not a major factor. People probably consumed less fuel with their stoves and fireplaces. Radiant bed pans with coals were common up until the 1930s and 40s.

Today our lifestyles are quite different. We don't bundle up and self insulate indoors during the winter, unless we are poor. Whole house gas or electric heating is the norm. Our bodies are used to operating at different temperature ranges than our parents or grandparents, much less than great grandparents. And we bathe a lot more. I think that's a good thing, but it has an impact that needs to be considered.

In the western world, if we look at old house plans and descriptions from 18th and 19th century American houses then something that may hit us is that it wasn't uncommon for kitchens to be in basements, or sheds in the back. Sometimes cooking was also done at a central hearth/fireplace. It depended. But toilet/waste relieving facilities and bathing (when rarely done) were always outside. People bathed in rivers, water holes, or wooden and later metal tubs out back. They used out houses. In Urban houses, when bathing was (rarely) done you may have had a small metal tub and the amount of water actually used was small. Only the rich had large bathtubs. Showers did not exist. Remember, showers aspirate water and hot showers generate a lot of vapor.

In some parts of rural Europe cooking was done in a detached place, but in many others and in typical urban European houses however the cooking was done at the central hearth. Either way a lot of water vapor just goes up the chimney or hearth hole in the roof. As for bathing, when rarely done, it was done in facilities outside. In some European cities from the late Middle Ages on you also had communal bathhouses. Up until very recently, after World War I really, people tended to do one weekly Saturday bath. Even after World War I people didn't bathe as often as we do today. My grandmother was a depression baby, she "washed up" with a wash cloth at the bathroom sink, just scrubbing her arms, legs, face and other parts most days. She only took a real bath a couple of times a week. My siblings and I lived with our grandmother for a few years in my childhood and the first thing she did was teach us how to "wash up" and stop all of that gosh awful water wasting by bathing daily like our parents insisted.

Outside of the West, in Japan and parts of East Asia communal bathhouses, sometimes in Buddhist temples, were used. People did not bathe at home unless they were part of the social elite. In the Middle East, North Africa and the general Arab world cooking was often done in a central courtyard - and hence an outdoor space. Bathing was done at communal "hammam" bathhouses. The bathhouse was one of the main social spheres, outside of the cofeehouse and mosque, in which people met, gossiped, and socialized. When bathing was done at home, the "ghusl" or bath was done with about one or two liters of water, about half slowly poured over each side of the body, with olive oil soap, scrubbing with a luffah, and then the remaining poured over, with tooth brushing and rinsing the nostrils with a quick sniff of water. So the amounts of water used were small, hence the amount of water vapor dispersed small. (in fact Old people still bathe this way even in cities, in some parts of North Africa and the middle east. Even in modern houses with showers they may have a small plastic tub and small ibrik, or water pitcher. Younger generations shower Western style though...)

You will find similar in many old world urban cultures, we don't even have to look at rural areas. People generated less water vapor, and did vapor intensive activities in different parts of their house than we do today. We live more thermally intensive lives today, we need more heat for our comfort, and we choose to cook and bathe in our intimate living spaces. In exchange for thermal efficiency we must tolerate amounts of water vapor that facilitate mold growth, poor air quality, and condensation. The solution is ventilation. Whether we can do this mechanically or passively is a different mater, but vapor barriers, insulation, and aggressive ventilation are requirements for us today.

I could be seeing things incorrectly and welcome thoughts and feedback!

Soap can be made in a low tech, traditional, eco friendly way. They make olive oil soap in the middle of North African desert countries. Soap should not be our enemy, I think..

Making soap requires energy, but burning a bit of kindling for a batch of soap that will last you a year isn't that bad, I think.

Dish washing without soap really needs old fashioned scalding hot water and scrubbing. Boil water pour over greasy dishes in a tub, let sit a bit, and scrub away.

Here's how artisans make olive oil soap in North Africa. You CAN use this stuff to wash dishes, hands, everything. My wife refuses to wash lingerie or socks with anything other than either French Savon de Marseilles, or a traditional Olive Oil soap like this...  

https://www.youtube.com/watch?v=1KZn31wB1FY

I use a Pilot metropolitan. I have two. Inexpensive, made in Japan, but they have great fine nibs and I write in little small letters so I need fine nibs.

The guy who makes Noodlers Bulletproof ink also hand makes very affordable fountain pens with old fashioned hard rubber, not plastic, feeds. He actually carves the feeds and then fits them into the nibs. But you have to play with it, heat it a bit, to get them to work right and I sadly lack the patience. His hand made pens aren't that expensive at all, however.

I love fountain pens, and grew up around them. My mom was a fountain pen nut.

I also like dip pens which, though very inconvenient, have a certain beauty. If you make a dip pen with a plastic or hard rubber feed you get something very similar to a fountain pen. There are a few out there on the market, and lots of old surplus ones like this.

My wife used She used dip pens in primary school in her home country, as late as the 1980s. She was amused when she stumbled over my little trove of pens

Malcolm Thomas wrote:Another quickie , You wanna get your hands on the Foxfire book ,

Hi Malcolm !The Foxfire books are amazing ! I stumbled on a near complete set at Half Price books last year. Imagine how much vernacular wisdom and know-how that just goes extinct over the years ! It's heartbreaking, but so amazing this stuff could be preserved.

If only someone could do something similar worldwide. Go to Rural Asia, Rural Europe, Rural Africa, record what the people are doing, how they naturally solved problems in the old days. The old timers worldwide have treasures of wisdom that can illuminate our situations all over the world.