Non Toxic Alternative for metal roofing for Rainwater Catchment

I have an earthship/cob house I just got done framing, and am looking for an alternative to metal roofing. I will be catching rainwater off the roof and using it in my day to day life, so it needs to be non toxic! I know people usually use metal roofing for this purpose, but would love to not use it because of it's cost and looks. I was thinking about cedar shakes, etc, but the pitch is not very steep so that might not work very well. I would love to make my own terra cotta tiles, but fear that would add too much weight to the roof.
I had an idea about using the scraps at lumber yards (where one end is bark) and skinning them and then carving them into the shape of terra cotta tiles. Then maybe sealing them with beeswax or canning wax. Just an idea though, have no idea if it would work.
Any ideas?
Thanks bunches!

where are you at? what about bark shingles?

I am in SE Missouri, and we get a ton of rain. The total rainfall for 2011 was 76", although that was an unusually large amount of rain.
I don't have any experience with them, but wouldn't bark shingles rot/give bugs a good place to live? I dont have a problem with replacing the shingles every now and then if the material is cheap (I can get a truckload of these scrap end pieces from the sawmill for $ But seems like that would rot fairly fast.

tulip poplar and black cottonwood bark last a long time. tulip poplar bark shingles have been used for long-lasting siding for a long time. to my knowledge, it isn't typically used for roof shingles, and there might be a good reason for that. just throwing an idea out there.

if either of those trees grow locally, there's a reasonably good chance you could get the bark for free, but you would have to do the work peeling it off felled trees.

ferrocemet should work fine

oohh, that might be the ticket Abe.
Ideas- put 6 mil plastic over the plywood on roof, then cover over with ferrocement? Is there a way to make ferrocement extra light? Maybe I could just put a thin layer down? With the plastic under it it would prob. be OK if it got a few cracks in it. I've never done ferrocement before, only soil cement.

you make it light by making it thin. You could do laminated FC, which is put down a 1/8" thick layer of fine mortar, then lathing (wire mesh), then another layer of mortar, then another layer of mesh, then mortar. It comes out about 3/8" thick, and weighs about 4 lbs a square foot.

you can add fiber to thin mortar and probably get away with one layer of mesh ad about 1/2" total thickness.

ok, here's what you do:

cover the whole thing in 6 mil plastic, make sure any seams overlap well and shingle (upper piece on top). Then, get some fine nylon screen, and cover the whole thing. Then, mix 4 parts cement, 4 parts really fine sand, 2 parts acrylic/latex, 1 part water. It will come out very thick (like sour cream), and paint it over the whole roof. after painting it on thick, let it dry overnight, then do another layer. Again, wait a night, then paint a final layer (you can skip the sand on this layer). Let it set up overnight, then mist it down, and cover with plastic for a week or two. Finish it off with a catchment-safe paint, and you're done.

You could even use cardboard underneath the plastic, just to give a form (gutter spouts, etc), and it should hold fine.

I did this without the plywood structure underneath: http://velacreations.blogspot.com/2009/08/latex-concrete-roof.html

google: Acrylic Latex Cement

Thanks Abe!
I couldn't get your blog to come up for some reason... the page pops up and then goes blank. I'll try it again later, maybe my computer.
Why the addition of the latex? Is this to counteract sun damage or something? Can this be in the form of regular latex paint?
What would be a catchment-safe paint? Would the addition of the latex make it somewhat toxic?
Thanks so much and sorry about all the questions!

the latex is a binder for the cement, and it makes it somewhat flexible, but also allows you to go really thin.

Latex paint won't work, you need an acrylic concrete additive. Some concrete bonding products are acrylic.

There are lots of catchment-safe paints. The Latex is not toxic, but I would still seal it with something (and the paint lets you paint it white)

Thats a very cool roof Abe. Any ideas on lbs per sqft? Not sure where you live Barn Kat but it might be wise to do some roof load calcs depending on your framing and worst case snow loads.

you did say none toxic; try terracotta.

Brian Knight wrote:Thats a very cool roof Abe. Any ideas on lbs per sqft? Not sure where you live Barn Kat but it might be wise to do some roof load calcs depending on your framing and worst case snow loads.

I can't remember lbs per square ft on that, but I imagine less than 3lbs per square foot. It is pretty thin, and I framed the thing using 2X6's. The framing is really just to hold the shape, once it sets up, it isn't really necessary.

George Nez (google the name) built lots of these with even bigger spans and lower quality materials (bamboo and muslin). Here's one example: http://www.ferrocement.com/Nez-George/George_Nez_1.en.html

Here's another description of the method: http://www.flyingconcrete.com/hypar.htm

It comes out a bit cheaper than metal roofing, and I think the weight is fairly similar. If you could make a form using plywood and/or cardboard underneath you could do a dome.

Alternatively, get some shade cloth, like 80%. stretch it over the building, and attach all around the edge. Then, make a pole in the center, and jack it up, stretching the shade cloth into a cone shape. Then, just cover with a few coats of the latex concrete, and once it is set up, remove the center pole. Easy as pie (in theory).

Terracota would be great, and heavy. You could always do fiber concrete tiles, too, but again, it adds a lot of weight.

did you mean to post some more info with that link, Ernie?

Nope

relevance?

here's a little house made with the acrylic concrete: http://www.ferrocement.com/Shelter-2010/post-1_5-2010.html

The stuff really is amazing, you can do a lot with it.

Do your due diligence on the toxicity of ferrocement, all cements for that matter.

Some say there are methods to make them less toxic, but standard methods do not take toxicity into account.
And it all leaches, and some binders used in mixes add even more toxicity.

Remember you'll have to live with it, so get the science facts on it before jumping in.

Ferrocement, like concrete, will need maintenance and repair as cracks appear. It is important to ensure that the ferrocement mix does not contain any toxic components.

For more information read the Q & A on ferrocement here -
http://www.greenhomebuilding.com/QandA/manufactured/ferrocement.htm

I would be looking into salvaged material myself. You can get some real finds. Even sheets of stainless steel. It is amazing what gets thrown away. Check with people who recycle materials - and they might actually keep an eye out for you.

Regarding water off a roof. Are you going to filter? Rain water is a great cleanser of the air and many places have acid rain because of it. Just because it falls from the sky doesn't necessarily mean it is pure. I was thinking of catching water off our roof, but then I got thinking about it and decided it was going to be too hard to ensure its purity.

After all, birds poop, lizards too, heck, all sorts of things like to be on roofs, and that is my water supply if I go that way. I can see that water off a roof having a pretty high bacterial count.

I would definitely filter it for drinking (we live completely on rainwater), but if you keep it dark and cool, you won't have any major problems. A settlement tank inline on the gutter helps keep a lot of the stuff out of the actual cistern.

You might be able to find something good in the salvage yard, though you never know what it was used for.

As to the question of toxic cement, I don't know how toxic it is. I know folks who have been drinking water from concrete tanks for decades, and just about every irrigation ditch is made of concrete (and fish live in them all the time). Concrete has been used for aqueducts and water storage for a very long time (probably longer than just about anything, besides bamboo).

I've never had to repair any ferrocement roof, but in that case, it would be pretty easy to do. Just slap on a layer of acrylic concrete.

What about bird poop? We have lots of birds ourselves and they love the roof. Not too fond of bird poop myself, nor do I think it would be very good for you.

Then again, we have spring water. I can see redirecting water for use around the property, but collecting rain water for drinking, well I wish the air was that clean.

Be very very careful with concrete or anything not intended for the purpose of using it. Without doing a lot of research, you don't know what was mixed in the concrete, and they aren't concerned about you drinking water which runs across it, since that wasn't its intended purpose. There is an incredible variation in concrete - be safe.

It might be okay, but without an analysis of it, you probably don't know.

if you put in a settlement filter, you'll catch most of that bird poop before it goes to your cistern. I don't worry about it. We don't have many birds on the roof, anyway, and bird poop is the least of my worries. If you are really worried about it, set up a biofilter in your cistern, and again, filter your drinking water. No big deal, easy fix.

Concrete can affect the ph of the water, which may have something to do with bacterial counts. I've never been sick from our water, even after 11 years of drinking the stuff. And I'm not the only one drinking rainwater.

Then again, we have spring water. I can see redirecting water for use around the property, but collecting rain water for drinking, well I wish the air was that clean.

you think the ground is cleaner than the air? Where do you think all of those contaminants in the air go? The vast majority of well water that I have come in contact with is a lot dirtier and filled with nasty stuff than my rainwater (sulfur, petroleum, nat gas, etc). But, maybe that is just my experience.

Be very very careful with concrete or anything not intended for the purpose of using it. Without doing a lot of research, you don't know what was mixed in the concrete, and they aren't concerned about you drinking water which runs across it, since that wasn't its intended purpose. There is an incredible variation in concrete - be safe.

It might be okay, but without an analysis of it, you probably don't know.

Yeah, you are right, though I am not worried about it that much. Again, concrete is used for transporting water all over the world. In my area, concrete is used for roofs and water systems all the time, so it is using it for the intended purpose. I think if concrete was really that toxic, it wouldn't be the material of choice for cisterns. There are millions of concrete cisterns in use.

I am more concerned about bacteria from bird poop, than the poop itself.

Regarding fish.

"Concrete Is Toxic To Fish
If you change this to read "large amounts of fresh, unleached concrete can kill fish due to alkalosis (high-pH)", then you would be correct. Concrete is harmless to fish once it has been leached. How do you leach it? After the concete has cured (30 days), fill the pond with water and add muriatic acid ("pool acid") to drop the pH into the upper 4's or low 5's. Keep adding acid to the water to maintain a very low pH. If you have a submersible pump which has no exposed metal parts or metal shaft seals, throw it in to circulate the water. Be aware that fresh concrete can soak-up a remarkable amount of acid. Keep dosing acid up for 5 days. Now let the pond sit and monitor the pH. If it starts jumping in the upward direction, hit it with more acid for another few days. If it looks fairly stable (ie, it stays under 6 for more than 24 hours) you are done. Drain the pond, scrub the walls with a stiff broom, hose-off the chalky white residue, and refill. Add declor, maybe a bit of baking soda if you have carbonate-poor water and you are done. The pH will still creep-up a bit for the first few years, but this will happen very slowly. Concrete by its nature will continue this trend for many, many years. To combat this, add a bit of acid followed by baking soda sufficient to drop the pH if it gets much over 8.6. The acid drops the pH while the baking soda helps to *stabilize* it somewhere between 8.0 and 8.4."

I raise fish.

Water from a spring tends to be very pure because as water passes through soil, then clay, then rock you have filtering, organic compounds are used along the way, as well.

Anything in the air, is going to be in your drinking water if you capture off a roof. What might be interesting to do is capture some water, then take it to have it tested, particularly for bacteria.

But, to each his own.

Have you looked at the book "Water From The Sky" by Michael Reynolds? He discusses all aspects of this subject, including various roofing materials.

so, the concrete is toxic due to the PH, but not because of some sort of toxic compound. rainwater is naturally acidic, and over time, the ph of a concrete tank will drop just with rain water.

but on a concrete roof, you are not looking at large scale leaching like that. If you capture rain water from a concrete roof into a plastic/neutral tank, the water will be acidic (I've done it).

I wonder what sort of ph the bacteria like? maybe it is advantageous to keep it high.

Cement/concrete are not very eco-friendly materials to use in permaculture projects.

From Wikipedia:

The cement industry is one of two primary producers of carbon dioxide, a major greenhouse gas.

Cement manufacturing releases CO2 in the atmosphere both directly when calcium carbonate is heated,
producing lime and carbon dioxide,and also indirectly through the use of energy if its
production involves the emission of CO2.

The cement industry produces about 5% of global man-made CO2 emissions, of which 50% is from the
chemical process, and 40% from burning fuel. The amount of CO2 emitted by the cement industry is nearly
900 kg of CO2 for every 1000 kg of cement produced.

In some circumstances, mainly depending on the origin and the composition of the raw materials used, the
high-temperature calcination process of limestone and clay minerals can release in the atmosphere gases and
dust rich in volatile heavy metals, a.o, thallium,cadmium and mercury are the most toxic.

Heavy metals (Tl, Cd, Hg, ...) are often found as trace elements in common metal sulfides (pyrite (FeS2),
zinc blende (ZnS), galena (PbS), ...) present as secondary minerals in most of the raw materials.

Environmental regulations exist in many countries to limit these emissions. As of 2011in the United States,
cement kilns are "legally allowed to pump more toxins into the air than are hazardous-waste incinerators.

I would use terra-cotta tiles rather than cement because the un glazed tiles have other benefits like acting as good thermal mass. also for any domestic use rain catchment I think it would be a really good idea to be very strict on filtration down to 1 micron or smaller. many birds carry parasites that need an intermediary host. mammals not being the host of choice these parasites can cause several problems. its pretty nasty some of the effects.

I agree with Ernie here. I would say it is the greenest roof material, all things being equal, and definitely as far as the least toxic catchment surface. The down sides to it are the weight and the availability. Storage and transfer will be the next hurdles if you are trying to stay away from plastic.

In NZ, pretty much everyone collecting roof-water has a galvanised iron 'corry' roof, either new or recycled. I grew up with them, I love the look and I'm not a builder, so I won't get into materials!
But the issue of contaminants has been raised. It really is an issue, as many birds and other animals carry salmonella and various other diseases. At the very least, I'd get a first-flush diverter and avoid trees overhanging the house.

if you have to move those tiles very far, you're gonna burn up any "green" value they had, because of their weight. What is their carbon footprint (there is a lot of energy required to move clay around)?

The concrete industry as a whole is a big polluter, but as individual sacks of cement, it comes out very low. One ton of cement (22 sacks) produces one ton of CO2 in it's making. If you do ferrocement at 1" thick, that's enough cement to cover over 1300 square feet. If you plant a tree, you just offset all the CO2 your roof produced in the making of the cement. Additionally, any free lime in the cement will sequester CO2 over time. You can put some limes plasters on your walls/etc and help sequester the CO2 produced in the making of the cement.

But the issue of contaminants has been raised. It really is an issue, as many birds and other animals carry salmonella and various other diseases. At the very least, I'd get a first-flush diverter and avoid trees overhanging the house.

How many people have gotten sick?

First-flush diverter or a settlement filter, and you'll be fine for the storage. Then, just filter your drinking water, no big deal, easy fix.

If you are really worried, dump some chlorine or bleach in there (yuk).

Doh! I totally spaced this but besides "Water From The Sky" by Michael Reynolds, I'd recommend adding Art Ludwigs "Water Storage" to your reading/research list. Between these two books, you can tap into a combined 50 or more years of first-hand experience in the very things being talked about here.

Rusty Bowman wrote:Doh! I totally spaced this but besides "Water From The Sky" by Michael Reynolds, I'd recommend adding Art Ludwigs "Water Storage" to your reading/research list. Between these two books, you can tap into a combined 50 or more years of first-hand experience in the very things being talked about here.

Yeah, I second this opinion. Art's book is really good, and discusses details of each material for water storage tanks (glass, plastics, metals, concretes, etc)

I dont know i do know that almost all brick manufactures produce a limited number of roof tiles. you could make the tiles yourself since they are only low fired a cob oven would do fine. you culd get whatever pattern you wanted for example by doing raku.

I think the material components of cement, the making, and the hauling those bags around might make it a touch spendy. I dont know for a fact, do you have any data on the cost of the whole production run of cement from the mine to the cast? I would love to see the numbers.

Raku is very very fragile, high temps in firing of pottery is what gives strength to the clay.

I haven't done the search on home-made roof tiles, but I did study pottery in college and I can't imagine anything less than a kiln firing would make lasting tiles. Very low fired clay must be covered, like adobe brick with plaster. Glazing would help, and does help raku pieces, but then that's a whole other can of worms. Do you have the temps for firing tiles Ernie? I'd be interested in knowing.l

Like cement's high cost of production, this high firing counts against the 'green' of typical roof tiles in it's use of energy for creation. As well as, trucking them into the site, as others have said.
However, tiles are much cleaner/greener in production and use than cement any day. Obviously a green roof is the greenest of them all, but you can only collect water from one in a rainforest climate like here in Oregon, and only after the roof soil is saturated. With soil filtered water one could worry less about the birds *grin*

if you absolutely have to collect roof water, I like the idea of homemade roof tiles. I think it would be worth it to find the right combinations to make one's own roof tiles.

Note: all man-made glazes bring the chemical issues back into play, and most natural glazes are just as bad. I never went as far as to learn to make my own glazes, my teacher did that, but I remember his warnings and the mask he would wear. My favorite 'natural' teal glaze was very toxic and required the use of gloves when applying. I believe some glazes are fairly safe after firing, but as I've said I'm not a glaze expert. So homemade tile making would take a kiln and some study, but I bet all the info is on the Net. Doing it yourself would make it much more green.

Great idea Ernie.

Ernie Wisner wrote:I dont know i do know that almost all brick manufactures produce a limited number of roof tiles.

the closest roof tiles to me are about 100 miles away. How much weight in a 1,000 sf roof?

Ernie Wisner wrote:you could make the tiles yourself since they are only low fired a cob oven would do fine. you culd get whatever pattern you wanted for example by doing raku.

That would depend on local climates and clay availability. If you have to bring in clay, you might as well go with cement, because you will be hauling less. My place has lots of clay, but no good for tiles, cause it expands drastically when wet. I love the concept of tiles, but I've gotta work with what I have, and it is much easier and cheaper to go with cement.

What is the cost in time and labor to produce your own tiles? What is the life expectancy of homemade roof tiles? These issues must be taken into consideration as well.

Ernie Wisner wrote:I think the material components of cement, the making, and the hauling those bags around might make it a touch spendy. I dont know for a fact, do you have any data on the cost of the whole production run of cement from the mine to the cast? I would love to see the numbers.

well, for one thing, you are only transporting only 1/3 of the weight, the other 2/3 comes locally in the form of sand. Concrete lasts for a long time, so the energy amortizes well. Plant a few trees, and your roof will outlive them.

Something to think about is that tiles are not a roofing solution on their own. They require a support structure, and there will be associated costs and energy related to that as well. I see most people using low quality wood for supporting tiles (in the developing world, anyway), and that means the roof will have a shorter lifespan, even if the tiles themselves would last longer. A properly made Ferrocement roof will be around until the walls fall, and even then, it will probably remain intact.

Another alternative is geopolymers or roman concrete (depends on local resources). Many of those materials actually sequester CO2, if that's your thing.

However, tiles are much cleaner/greener in production and use than cement any day.

Not necessarily. Low-quality tiles (or substructure) that must be replaced within 50 years, and/or were shipped very far would definitely have a larger impact than regionally-produced cement. You save energy on the temperatures/heat of firing tiles, but not in the transport and durability.

Jami I will get that data for you; used to have it on the top of my head but the years of not using it have made it fade.

Abe one thing i do know is tiles are made with ball clay and unless someone is sitting in the middle of a bentonite patch mixing some sand in will make stable tiles. if you only have bentonite then you mix in enough gravel fines and you got a good tile it just takes testing.

Weight would be a factor most tiles are 3/4 inch thick however thats not totally necessary either. low fired tiles work just fine all over the world with no glazes. So i will look up the temps and match them to the oven. since the oven gets to cone 4 if fed correctly i believe we can fire pottery. but i want to check before i make a statement like that. I will also do an experiment while we are in portland (I have just the oven) to see if a can biscuit fire the local clay into a tile. if i was to build a cement roof i would go with roman cement. probably use hydraulic lime to ensure the roof would hold water properly. I am not sure on the weight what would work better roman cement or clay tiles. of course you could make a living roof and plant moss on it so your water is filtered before it gets to you. thats just cardboard covered in visqueen and 2 to 5 inches of dirt. you can grow plants and filter the water at the same time.

just something to consider.

Ernie Wisner wrote:Abe one thing i do know is tiles are made with ball clay and unless someone is sitting in the middle of a bentonite patch mixing some sand in will make stable tiles. if you only have bentonite then you mix in enough gravel fines and you got a good tile it just takes testing.

I'll try mixing some sand in, and see if I can make anything that won't crack like crazy. When we first started building here, we tried to make adobe blocks by hauling up sand, but we could never get a mix to work. So, we tried some cob with a lot of straw in it, and again, it just cracked like crazy. I never found a sand mix that would keep it together very well. We did get one mix to hold up enough that the cracks were not structural, but as soon as water touched it, it expanded and fell apart. If I could figure it out, it would revolutionize the local roofing industry.

but, I assume it is not very practical, because the locals don't use it in the traditional buildings. But below us, in the river valley, they make lots of adobe (several adobe buildings over 200 years old). Our soil is a dark maroon color, whereas the adobes are the typical tan color. The traditional roof was big pine poles covered with planks, and then about 18" of adobe on top. Most folks use concrete or metal these days, though.

I assume that you have to break up the dirt/subsoil, and then do something so that you are working with relatively pure clay (not a bunch of rock, silt, organic matter, etc) for tiles. Do you have any links/resources for making roofing tiles? If I could get a mix that worked well, I could test a small roof, like on a barn or something to compare with FC. I've seen stuff on youtube for making roofing tiles, but nothing describes getting the raw materials.

Since we are on the subject of tiles, here's an alternative tile method that doesn't require a supporting structure:
http://www.lowtechmagazine.com/2008/11/tiles-vaults.html
http://www.notechmagazine.com/2011/12/sustainable-urban-dwelling-unit-sudu.html
http://sudu1construction.wordpress.com/

We tried that method once, but combined with hauling tiles a long distance (and cost!), and a significant learning curve with this method, we didn't go further with it. There are a lot of resources online about that method under Catalan vaults, Tile vaults, Gustavino Tiles, etc. If I could make my own tiles (could I do it without firing them?), that would make me work harder at beating that beginner's curve. I love the look of tile vaults.

Ernie Wisner wrote:of course you could make a living roof and plant moss on it so your water is filtered before it gets to you. thats just cardboard covered in visqueen and 2 to 5 inches of dirt.

that's a heavy roof when it is wet. Make sure you have a good structure supporting 5 inches of wet soil. Do you have some links of a roof like this? I would love to see a moss roof, that would be beautiful.

Ernie Wisner wrote:if i was to build a cement roof i would go with roman cement. probably use hydraulic lime to ensure the roof would hold water properly. I am not sure on the weight what would work better roman cement or clay tiles

roman cement would win, no doubt, cause you can add reinforcement, and reduce the thickness considerably (similar to ferrocement). Additionally, the roman cement would not require a supporting structure (it IS the structure), if you did it right. Finding the materials locally could be a challenge, though.

and one more tile vault link, just cause they are beautiful: http://www.notechmagazine.com/2011/12/timbrel-vaulting-using-cardboard-formwork.html

I'm planning on making my own floor tiles. I don't know if these would work for roof tiles or not, but here is a page about self-glazing wood-fired tiles:
http://ceramicartsdaily.org/education/college-level-ceramics-assignments/recycled-glass-and-clay-tiles/

There are other sites with similar methods, but that's the one I bookmarked. By making the tiles from 75% powdered glass and only 25% clay, firing time/temperatures are greatly reduced. Also, the tiles dry and are ready to fire sooner and the quality of the clay is less important--less clay and less water mean less shrinking and cracking.