Masonry/Rammed Earth/Compressed Earth Block WOFATI: Is it possible?

I will be located where there is a lot of granite, and on the same property, clay and sand. I would love to know what people think about using masonry as structure for the support of the huge green roof. I don't have anything against using lumber for construction, other than that the trees I do cut will be busy making soil in hugelkultur beds. I would love some feedback.

-CK

Masonry is great but its only one component in the system. In Canada, you will need insulation and preferably, lots of it. Green roofs are heavy. It would be very challenging to create a roof out of your site available masonry materials for all but the tiniest of structures. You need a material that will span between the walls which is traditionally wood.

Thats great you want to preserve wood for hugleculture and topsoil. Airtight and continuously insulated is probably more important than the upfront materials you will need to build because the thermal envelope will effect how much wood you burn for many years to come. Unless, you wont be using a combustion appliance as your main heat source which would be my preference as well.

I know this is not a permaculture idea, but couldn't you use steel beams to get the span you want and pack the masonry around it for more insulation and to cover the look of the beams? That way you would not have to use the trees and you should be able to get a roof structure that would be more than sufficient to support what you are thinking.

The beauty of Permaculture is that there are so many ways of doing things! I dont see anything incorrect about using steel. Its often the only choice in necessary components with heavy green roofs. A better permies practice would involve sourcing some pre-used beams.

Just what I was thinking. It would clear your conscious, so to speak, if you could find used ones.

To be clear, I am perfectly happy to use lumber where required. One idea I've been toying with, though, is that of function-specific forms; what would the opinion be of designing a form set for compressed earth block that would allow for, say, an arch? Or for that matter, would it be possible to build forms in the shape of arches, and then make them of rammed earth? If neolithic cultures could build megalithic structures, I have a hard time believing we can't figure out a way to do it ourselves, with thousands of years of understanding mechanical advantage and physics. I think if the system is properly planned out and tested, it should be relatively easy to use barrel vaults, arches, and pillars in a pretty traditional manner to build what I'm thinking of. I think that, with masonry, it's the smaller structures that would be harder to do, considering the nature of the arch.

Yes, I do realise what I'm proposing. I'm envisioning something with the solid feel of a castle and the proportions of a gothic cathedral, just with a forest/pasture layer of, oh, 8 feet or so, maybe more, on the other side of the ceiling (I believe Paul's recipe for a WOFATI green roof calls for 4 feet under a moisture barrier as insulation, and another 4 on top for growing, but I may be inflating them a bit).

I was also thinking about making a form for a slightly concave hexagonal tile that would allow for the construction of domes, but I get the feeling that it might be a little more difficult to make work with all that dirt on top of it. But theoretically, it too should be possible.

For all this, I was thinking that fibre reinforcement would be necessary, but I would try this within individual blocks using hemp or some other fibre I could grow on site. I was also thinking of using it between courses. I would have to ensure that individual fibres in both cases were encased within the material, the blocks and the block slurry that is used as mortar making the finished structure into a single piece as opposed to forming layers that would separate under stress. I was also thinking of upping the pressure used to form the blocks as high as I can with the materials I can afford. I am also not going to sneer at using 10% Portland cement in the mix.

As to insulation, I work in a bindery, so there's lots of paper shreds from finish trimming and such. While I don't think I'd do so without isolating it from the living space, I could see a perimeter of bags of the stuff between masonry and infill, acting as insulation.

Right now, I am wondering about what natural materials could be used to make a glaze for bricks, or tiles, for that matter. If there was a glaze, I could see a roofing system made of one or two shapes of tile, just a slightly tapered cylinder, you guys know the one I'm thinking of, two layers of half-cylinders, the top one convex side up covering the ridges made by the sides of the bottom layer, concave side up, looking like adobe bamboo when it's done.

I may be wrong, but on the other hand, it may be that there are ruts that we are encouraged in to when we are educated in a thing, and that sometimes an out-of-the-box perspective can be useful.

I really appreciate all the input. I like it when people help me to keep from accidentally doing something lethally foolish.

-CK

Hmm, an out-of-the-box solution like half-cylinder tiles? You mean like the ones that have been used around the world for thousands of years?

In less freezy climates, you don't need glaze, but if frost is a concern, glaze on tiles plus high firing temperatures will make them water resistant and durable. Traditional glazed tiles are lead based, very easy to do (I understand) and of course toxic to handle the raw materials or the leaching runoff from them. Whether you can make (glazed) tile locally depends on your resources - what kind of clay is available, and what amount of wood for firing.
Tile kilns were traditionally built next to a major building project, used as necessary and then abandoned/demolished. It is quite feasible to do it yourself IF you study clay and kiln building/firing techniques and have the time and energy to invest. Hands-on experience is vital.
There are unfortunately not so many simple low-fire glaze substitutes for lead, but you can find recipes in pottery/ceramic references. The higher the firing temperature, the more likely you can use local materials to do it. It will be far easier if soundness rather than esthetics is your main concern.

Thanks Glen. I'm glad my description was clear enough to understand what I was trying to describe. Do you know if there's a proper name for the style? (And I was aware that the specific tile form is old as dirt, thank you.)

I was wondering if a properly grouted roof in this style could be made watertight in such a way that it would stay that way under the WOFATI roof. I know if you tried that with any traditional shingle, the saturated material sitting on top of the roof would allow water to wick up between the tiles and eventually inside. I was wondering if this might work in the way I want to use it, or if I'd be better off just going the HDPE or pond liner route.

-CK

Howdy Glenn, welcome to Permies ,and a great first post there.
Sounds like you have experience with clay and pottery ? If so , some of us have been wondering about using a rocket stove to fire a kiln. If you could help ,please start a new thread on that.

I second that request. I was wondering specifically if it would be possible to have a rocketmass heater kiln, or one for rapidly curing wood, or for making biochar, for that matter. Unless I'm mistaken, these processes have much in common.

But to the original point, I'd love to be able to fire pottery. Tapered half and whole cylinders could have many applications for plumbing and irrigation, or for replacing plastic piping in the ground.

-CK

A newbie to this forum... just passing along some thoughts. First, see Nader Khalili's book, "Ceramic Houses and Earth Architecture" for an approach to firing your entire structure in place, not as separate bricks and tiles. Second, he mentions that a slurry of common salt makes a good glaze. Just be sure to avoid the chlorine gas that is liberated during firing.

Also, regarding the idea of multi-layers of tiles forming a roof, google and check out the works of architect/engineer Rafael Guastavino who built beautiful thin-shelled large-span masonry vaults and domes in the late 19th and early 20th century, including such prominent buildings as the Terminal of Grand Central Station, the Cathedral of St. John the Divine in New York City and the Boston Public Library. These were formed using multiple interlocking layers of thin tiles. Very strong and light weight.

Thanks Jack and welcome to Permies!

Brian Knight wrote:The beauty of Permaculture is that there are so many ways of doing things! I dont see anything incorrect about using steel. Its often the only choice in necessary components with heavy green roofs. A better permies practice would involve sourcing some pre-used beams.

I think it also matters how one obtains the steel, were one to use it. We plan on building a root cellar, using concrete. It will be earth-bermed, and an attached accessory building to our main structure. A couple of weeks ago, I found several panels of thick aluminum rooing material. It was being thrown away in a dumpster, remnants from a major local construction project. I also obtained a thick, 11'-long 3x3" L-beam, 3/8" thick. It is now sitting around, awaiting its eventual use as a roofing structure (poured concrete roof) ... totally free, plus removing crap from the landfill.

TO me, that's within the spirit of the whole permaculture thing. The end result will be a root cellar that should last way long after I'm worm food.

For the question of using a rocket heater to fire a kiln, the two are mutually exclusive. A kiln must be warmed very slowly and evenly over a period of hours, before getting to high temperatures, and rapid temperature fluctuations any time during the firing are detrimental and possibly fatal to the contents. You need slow gentle heat transitioning evenly to intense 2000+ degree heat.

That said, there are some resemblances between the firebox design of the two. It is common to have a fire that draws sideways under the ware chamber and then turns upward, or even for some styles of kiln a long slightly sloping fire path through the whole kiln followed by a vertical chimney. Kiln design and operation is a complex subject with a lot of available literature. My direct experience with wood firing is mostly research into medieval English kilns and pottery.

A form that I have found to work well at experimental scale (around 5-6 cubic feet ware chamber) has a 3 to 4 foot long horizontal firebox about 16" wide and high, with the end below the ware chamber and slots/holes allowing the flames to rise through it and exit out the top. The ware chamber is an open-topped cylinder, with fragments of pottery, clay "pancakes", and/or turf clods on top of the contents to hold in the heat while allowing free flow of gases. The exact proportions influence the effectiveness and vary with overall size, but I have found this to be about the lower limit for decent firing. Any smaller and it simply cannot generate the sustained temperatures required. A larger (and filled) ware chamber makes for more even heating; common medieval styles were often 6' x 9' (oval) with two fireboxes, one at each end, for thorough heating. The total height of originals is unknown as none survive to full height, but it is thought that they would have been about as high as wide. THe more compact the shape, the more efficient and effective at even heating. The general style still in use through the nineteenth century developed into massive structures on the order of twenty feet across and high, so there is no reasonable upper limit to size for a woodburning kiln as far as a homesteader would be concerned. One of my experimental models of about 8 cubic feet was able to get the beginnings of ash glazing and near stoneware firing range, and I could improve on that now.

All of these kilns were built on site with local clay and dried grass/straw temper (cob, really) and first fired while still wet. They have never exploded on me, unlike the pottery contents which MUST be bone dry and heated very slowly to avoid steam explosions.

BTW, the semi-cylindrical tiles are commonly known as barrel tile.

Salt glaze is an excellent high-fire technique though the chlorine liberated is not friendly, and has been known to be environmentally hazardous. The final result of it as it combines with the atmosphere is hydrochloric acid, after all. A recent alternative is soda glazing, which yields similar results with much less hazard or harm. Look it up for more technical detail. You do need high temperatures for these to work, but for roof tiles you really want high temperature for stronger less porous products anyway.

Ash glazing is a natural alternative or version of salt glazing; mineral ash from the burning wood settles on the firing pottery in interesting patterns and melts to form a glaze, which can be thin or thick in spots, but always irregular and concentrated on surfaces where ash can reach and settle.

I was wondering if a properly grouted roof in this style could be made watertight in such a way that it would stay that way under the WOFATI roof. I know if you tried that with any traditional shingle, the saturated material sitting on top of the roof would allow water to wick up between the tiles and eventually inside.

I wouldn't bet on it. It might work if you had a loose layer above the tiles for water to drain away in (gravel or another layer of tiles laid on top of the official ones), but earth in contact with the tiles would wick damp through to the inside even if the joints were all perfectly grouted. (Unless you could fire the tiles to stoneware... very unlikely.) I think rubber/plastic will be the most effective and by far the easiest method for waterproofing.