Stucco on a roof

I can't find much googling this, just one article that seemed speculative rather than informed.


I think stucco wall is stucco/mesh/waterproof but breathable membrane/sheeting.
This seems like a cheap,easy process,especially if looks don't count for much.

So,can this be used on a roof?
A cementious roof could be long lasting, cheap, easy to diy,and safe for rainwater collection.
Because it's a roof, amd breathability isnt key,plastic sheets could be used as the membrane.
The stucco protects the plastic from UV damage.

Adler Burns relates a story of building something like this. His version uses cardboard sheeting, scavenged plastic for water proofing and discarded carpet instead of mesh! So freaking cool!
I've never been able to stop thinking of this as a great flat roof.
I would want to regularly walk on it. The flexing from weight  that might prove to be too much.
But cracks in the stucco layer might not be a huge deal,as long as it continues to protect the plastic.
The mesh should help keep it together.
Adding used fiberglass insulation to the mix should make it even more crack resistant,but NOT more insulative.
Adding styrofoam could help with that,but might lower the wear resistance.
Perlite would be insulative but more wear resistant.
Either would lower the density of the mix.
Coal slag or garnet abrasives could be added to the mix to further improve wear resistance.

The building I want to try this on will be a shed at my grow yard.
I would build the walls strong enough to support a second story.
I would build the roof as if it were the floor if that second story.
Over the floor,I would build this stucco roof.
On this roof I would build a greenhouse/ shade house frame.
Winter time the greenhouse receives escaped heat from and offers a insulative layer to  the space below.
Summertime the shade house shades the roof of the work space below,and offers a place to chill.
Grape and hardy kiwi vines suck up the sunshine.
A recirculating solar powered misting system offers some cooling,but it is very humid here,so any evaporative cooling effect is minimal.

So that's the crazy plan.

My questions to you:
Can a stucco roof work?
Can it be durable enough to be walked on?

Stucco crumbles pretty easily. Many of the broken pieces will have sharp edges and will cut through the plastic. I foresee a huge mess. Cheap? Maybe so, but not structural, not long lasting, unfortunately.

A different mix perhaps?

There's a reason that there aren't many places that regularly install flat roofs. They're expensive to do right. They tend to leak. They don't bear heavy loads well (like snow & ice). It's much cheaper, long lasting and reliable to build pitched roofs (particularly since you are in Ohio). I tend to prefer metal roofs. They are really, really cheap and if you paint them every 20 years or so will last your lifetime. There are places on a farm/homestead were you can try to go cheap. Using used electrical parts, installing a poor roof, using badly fitting windows where there is winter, are not among them.

There's no question that concrete can be made watertight. I have been on a ferro-cement boat. They are very heavy and the materials must be top notch. It would end up being a very expensive and heavy roof if done in the style of better ferro-cement boats.

I don't think any of the standard stucco mixes, would stand up. The most expedient and long-lasting way to deal with a flat roof, is with ballasted EPDM rubber. The same material lasts longer, if it simply has stones covering it, compared to being glued to the substrate.

if it s just about protection from UV: here people have rot resitant carpets on patios etc.
they have little plastic knobs underneath them to improve drainage.

but i m not sure if they would be enough to protect the roof from foot traffic.

what about building a second floor above the roof to walk on? like you would build a wooden deck/patio thing?

or EPDM with gravel and concret-pavers where you walk?

Thanks for the replies.
I have already implemented this construction style on a custom built countertop and  the floor of a mobil chicken coop( my little girl dubbed it "The ChookWagon")
The wooden structure of the counter remains dry,despite the built in sink. No plastic was used,just cement over window screen. Time will tell if this holds up.

I think I will build a walkway, osb over 4x4s, plastic, netting, and my "stucco" on top of that.
If it survives being walked on and the ground beneath stays dry, I'll be ready to go forward with it on a roof.
I may even build a 1foot square chunk of osb/plastic/netting/stucco, and weigh it,first the osb by itself, then with the rest applied.
That way I'll know for sure how much weight I'll be adding to the floor.

I like the idea of just using outdoor carpet,but Iike experimenting with cheap/free stuff even more.
I want a deck, but after refinishing/rebuilding a handfull of decks for pay, I knew  I really didnt want to do it  for free,so my deck will need to be "different".
I am trying conserving space at my grow yard,stacking leisure space on top of workspace.

that outdoor carpet is 1,99€ per m² over here. But here you could get it probably used for free.

good luck with your experiments. would a cheap acrylic primer/sealer help as a finish?

I think I would integrate the waterproofing into the mix, latex concrete style.
Any waterproofing finish in or on the cementious layer would be a welcome redundancy,due to the layer of plastic.

The stucco will flex and rip up the plastic. Stucco needs to be sealed or it tends to suck up water, get crumbly and break apart (it is very subject to freeze/thaw cracking). Even wind is enough to break it up if the stuccoed surface has the slightest flex; walking on it will destroy it in a hurry. And if your roof isn't constructed to hold elephants, you will soon have stucco inside your building, on the floor, along with the rest of the roof; it is as heavy as any other cement product.

Signed, the person who spent the previous summer repairing and patching stucco

A suggestion: continue as planned to 'stucco' your roof, but place posts regularly through or around the roof to support beams / joists to create a permeable deck above the roof. This will relieve the 'stucco' of the requirement of having it withstand the live-load, which, as the previous posting stated, will eventually crack and crumble with the freeze/thaw situation you face. Good luck. [PS: I do, however, question the use of portland cement for anything (which, from your description, the stucco you are planning on using has portland cement). The manufacturing process of portland has quite a large carbon-footprint]

Have you ever heard of HardiPlank siding and shingles ?   It is cementous and the reason why it can work as a roof is that it is in the form of
shingles which dont have to worry about expansion and contraction in the hot sun and cold winters.  BAsically each shingle expands and
contracts and the water proofing comes from the overlapping  .... and of course the shingles themselves are waterproof.  The HardiPlank
and competitors have mesh material or fibers throughout the material and that makes them tough enough to withstand walking on without
cracking.  Basically this is man made slate.    In your case I realize you are using the concrete to shield an underneath plastic or vinyl layer
but as has been pointed out when the cracking begins it may overwhelm the plastic below  and damage the watertight barrier.  

However, are you aware of the progress that has been made by mixing portland cement into Exterior Latex paint ?  If I recall correctly there
have been some that have taken variously jute,  polyester, window screen and cotton or other fiber canvas etc and put this material on a roof  over nearly
anything and put several coatings of the latex portland cement over it and they are achieving long lasting water proof results in part because
I think it is somewhat flexible.   In the article that I read,  they did not put the canvas over anything except air.  They merely strung the
canvas over rafters and painted it in place and that served as the entire roof.

Back to your concept of concrete roofs.   I believe it could work if you used concrete tiles or squares that allowed miniscule movement between
them without forcing damaging cracks to occur even if they did not overlap like shingles.   Of course if they did not overlap then something
underneath them is handling the water proofing task and the tiles are only supplying the UV protection and protection from abrasion if
you ever walked on the roof.

You can absolutely do this. 3 to 1 sand to Portland use some old fencing as a reinforcement. You need a temporary form to hold up the mortar. We used plastic sheeting over boards between the rafters. This was an irregular shaped roof so we went with the ferro cement style roof. It was cheaper than painted metal. We did a rough coat let that cure overnight then a finish coat. Finally a coat of pure cement painted on mixed like heavy cream to waterproof. It is still standing and waterproof.

Don't know much about this personally, but I do remember concrete/cement roofs on my last visit to Bermuda.  At least it's a place to start.

I'm currently building a new 2400 sqft house. I'm going to do a stucco roof. However I'm going to fiberglass the roof first, turtle shell the house. I'm going to put down 4" thick 2lbs styrofoam over fiberglass adhering it with polyurethane glue. The testing I've done I've used Quikrete foam coat mix. I will do a base coat, then a colored design pattern. Lastly I will use a acrylic masonry sealer. The purpose is to make a roof that is isulated externally and it should never leak.

Nice plan Anthony! I had to Google the foam coating, looks a lot like fiber cement, in its structure.
No need for a mesh layer, it goes right onto the foam, perfect!

I might not want a wall with a foam layer but a roof,sign me up!

It reminds me if the Wedi system:
https://www.wedi.de/en-us/product-systems/shower-and-wet-room-systems/building-panels/

Their panels are expensive compared to their component parts,but their glue is very, very good.

With the quickcrete foam coating, and their glue, quick, cheap water tanks ,bath/shower enclosures and insulated roofing should be easy to do.

Excuse me while I fantasize about a roof that's essentially a solar pond 😍

More down to earth, this really could make solar or wood hot water tanks even easier to build.

Stucco is a durable material that can be designed to give your home a unique look for years. Stucco is resistant to fire, rot, mold, impact and termite infestation. Depending on local climate conditions, the finish on stucco homes can last as long as 100 years.