Instructables
Picture of Latex Concrete Roof
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Latex, or acrylic, concrete is an underused and little known form of concrete for the DIYer, which is a huge shame. It has so many benefits, especially as a roof (or unique art project). It is:
  • Lightweight - the support structure does not need to be as extensive as with other materials.
  • Fast Setting - you don't have to be as scared of clouds on the horizon as with concrete.
  • Goes Quick -  almost equals the speed of putting up metal roofing, which is a material we often avoid as it does not last as long, or look or sound (in rain) as nice as concrete options.
  • Inexpensive - for its strength, durability and speed, it is cheap.
  • Artistic - it allows for many different designs, though a pyramid structure seems to be the most efficient.
We’ve used latex concrete for the roof of our cisterns (see steps 8 and 9 of How to Make a 6000 Gallon Water Tank), as well as the roof of the kids’ bedrooms. It would also be ideal as a quick and exceptional-looking porch. 

The shape and style of your latex concrete project depends almost entirely on your imagination. Within this article, we’ll run you through both the overall principals and the more specific details, and we hope you go on to make some wild looking creations.

For more information on concrete or other building materials, visit the shelter section of our site.

For more information about this method of building, please read "Latex Concrete Habitat" by Knott and Nez
 
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MarkML1 year ago
Great job with this Instructable! This is fascinating. I haven't seen any how-to on this type of construction before. I'm envisioning many different ideas where I would like to try this. Also, very helpful comments. Thanks!
pattiemelt1 year ago
Could this be applied using a stucco/plaster sprayer? It seems like spraying would be easier & quicker than brushing/brooming it on, and would also allow for a more even layer on each coat.
velacreations (author)  pattiemelt1 year ago
At first, spraying looks like it would be easier, but the distances involved are bigger than you think, so you would have to work out a scaffolding system to get the sprayer closer to the roof. The nice thing about the broom method is you can dump a lot of material on the roof all at once, and then spread it out. It goes fast.
PitStoP1 year ago
This is great. Is this something that has been used for years or is this something you came up with yourself?
I'm wondering if this roof will last as long as a regular shingle or metal roof also. I have a few question on this.
How many Acrylic Latex gallon bottle did you actually used on the 30 x 15 roof of the kids room? Also I have a large 30' x 24' shed that I'm turning into a garage/workshop and it has metal roofing at this time that is starting to rust and I was thinking of painting, do you think it would be a great idea to do this on this roof and if so should I do it (add the cement) on the existing metal roof on the bare metal itself or add maybe billboard material before adding the cement? Thanks for the Instructable.
velacreations (author)  PitStoP1 year ago
Dr. George Nez and Dr. Albert Knott developed this technique for low-cost roofing in Africa. They have a book, which I highly recommend, called "Latex Concrete Habitat" (there's a link to it in the introduction above).

We used 4 x 5 gallon buckets of acrylic on the kids rooms (33 ft by 12 ft), so 20 gallons.

To add to metal, I would lay down a vapor barrier (black plastic), then netting and the concrete. I don't know what your structure underneath is, but make sure it can hold the weight, first.
EmmettO1 year ago
Cool technique, would you say that a latex concrete roof is walkable? What if it's fully supported by say plywood underneath? I've been trying to make a walkable roof for the last year and so far epoxy hasn't worked and regular roof coatings are not up to being walked on. In my case, I'd be just going over my existing epoxied roof which is mostly waterproof but started to photo and or heat degrade so the concrete would really just be a coating.

So in the scratch coat is 50/50 water/acrylic and just portland? How much portland per gallon (or 5 gal) of liquid?

Again, the brown coat has the same liquid proportions but how much of the sand/portland mix per gal of liquid.

For the finish coat, you mix paint into the cement or are you saying that that you won't use as much of the concrete mixture? Is the finish coat material more or less the same as the scratch coat?
velacreations (author)  EmmettO1 year ago
It is walkable, though we tend to stay to the parts that have structure underneath. I would not want to walk on it regularly. With plywood underneath, it could be done.

The ratio of portland in the scratch mix depends on your situation, and the moisture content of your portland and/or sand mix. For each gallons of liquid, you'll need at least another gallon of dry mix, maybe a bit more.

The finish coat is the same mix as the scratch coat, but you can make it a bit more liquid, and then paint it on thinner than the other coats.
kbearvulcan4 months ago

How would this type of roof hold up to negative degree temps. I live in Montana and it gets very cold up here.

kbearvulcan4 months ago

I live in Montana and wonder if it would hold up to the weather here. It isn't the snow I worry so much about but the negative degree temperatures. It looks like it would be a great roof otherwise for the craft shed I want to build. I am slowly trying to work away from the grid.

crazypj11 months ago
That almost seems too simple?
Garden shed needs a new roof, may be ideal for practice.
Lifespan should be much higher than sheet metal or wood/tar shingle or even plastic as that tends to crumble with UV exposure
Could latex paint be mixed with final coat to have it self coloured?
poofrabbit1 year ago
Just wanted to say congratulations on being a finalists in the Concrete & Casting Contest! This was a fantastic instructable! Good luck!
velacreations (author)  poofrabbit1 year ago
Thanks a lot. There weren't that many entries in this competition, but it seems like the quality of all of them was excellent.
nthomas121 year ago
Really love this technique, I can think of lots of sculpture and design applications!! Thanks. I wonder if there are material data specs available for all those New England people wanting to know about snow loads!!
bsims11 year ago
MgO is a far superior product to portland with additives for this and any other type of art or construction project.
http://www.instructables.com/community/Ever-heard-of-Ceramicrete-MgO-cement-Magnesium-c/
zmiriam1 year ago
Thanks for this terrific instructable. What about using this technique to make large panels or tiles that could be overlapped on a roof structure such as trusses? Any thoughts?
velacreations (author)  zmiriam1 year ago
you would probably need more reinforcement for that, and they would have to be a bit thicker. But, it could be done. Do some research into microconcrete tiles, it's similar to what you are talking about.
sconner11 year ago
That wouldn't fly here in New England.
We get lots of storms and snow depth.
Plus building codes.
velacreations (author)  sconner11 year ago
our storms are significant with 50 mph winds on a regular basis.

As far as snow is concerned, it will hold up, as long as the structure beneath the concrete is able to hold the weight.
acrylic what ?Acrylic may refer to:

Chemicals and materials

Chemical compounds that contain the acryloyl group derived from acrylic acid
Acrylic fiber, a synthetic fiber of polyacrylonitrile
Acrylic glass, a term for poly(methyl methacrylate) (PMMA)
Acrylic paint, fast-drying paint containing pigment suspended in an acrylic polymer emulsion. It is a common medium used in modern fine art/art
Acrylate polymers, a group of polymers (plastics), noted for transparency and elasticity
Acrylic resin, any of a group of related polymers formed from a mixture of monomers selected from the C1 to C8 acrylate esters, methyl methacrylate and, often, styrene
Other
velacreations (author)  old pennywise1 year ago
Acrylic concrete additive
I mean do you think the stress load would be too much under a foot of snow? Would it hold up?
velacreations (author)  shawnlambert1 year ago
I think it would hold just fine, as long as your supporting frame can handle the weight.
Love the idea of this. I'm looking to create a central entertainment area in a social project and this could well be a roof system that would work.
technex1 year ago
Your concrete goes off quicker in a plastic form because it is non-porous and retains water better than wooden forms. Concrete curing is not a drying out process but actually a reaction with water so keeping the concrete moist allows it to cure quicker.

You may have seen big construction projects 'ponding' large slabs of concrete by using a raised form and filling the top with water, this is to aid curing through the full depth of thick slabs such as are used for foundations.
How does it hold up to New England snow?
velacreations (author)  shawnlambert1 year ago
I have no idea, we've never built one in New England.
neddy11 year ago
Great instructable! Love to see concrete work that's outside the box and showcases what concrete is capable of.
mtngrown1 year ago
Wow! This is an amazing 'able. I've been wanting to try some of this kinda thing for a while. Think I'll give it a shot.
bsims11 year ago
Has anyone ever worked with MgO cement? MgO replaces the Ca found in portland cement. MgO cement makes a concrete that will incorporate cellulose and other organics into the crystalline structure. absorbs CO2 instead of generating it, is an order of magnitude stronger than portland, does not require wetting, and cures in minutes. So basically, you can take some burlap or old blanket and paint this stuff on, then fill the void with straw and cement so you can make super strong, light and thin structures.
I have looked for it locally but it does not seem to be in available to consumers in the US, probably because of the lack of sheep crap which is the typical source of Mg. It is amazing stuff.
http://greenhomebuilding.com/articles/ceramicrete.htm
velacreations (author)  bsims11 year ago
That is very interesting. There are a whole range of cements/geopolymers.

Is MgO cement something we could make at home?
Awesome..very practical.Has any form of of this been used in boat building, bridges or piers or any underwater structures? Thanks
The closest in boats are ferrocement boats which according to wiki was first known about in 1848 France
velacreations (author)  richardfireone1 year ago
not that I know of, but possibly.
foobear1 year ago
This was enlightening thank you!
Kinnishian1 year ago
This is pretty cool! I'm curious if anyone has experimented with paper concrete and acrylic.
rmacchio1 year ago
The roof on my house now is shingled, I was planning on adding a metal roof on top but if this is a better option and more cost effective I'd like to go this route
SDX421 year ago
This looks fantastic!
I'm just wondering: how durable is this? What happens during a storm? Does the concrete become brittle?
velacreations (author)  SDX421 year ago
the concrete remains somewhat flexible, due to the acrylic content. This roof has survived a number of storms and winds in excess of 50 mph without issue.
rmacchio1 year ago
Would this be a practical and more affordable option to reroof a house with metal roofing?
velacreations (author)  rmacchio1 year ago
it depends on the support structure underneath the metal roofing. It could be done, but I hesitate to recommend anything without knowing more about your situation.