Grancrete – Spray on cement…

Grancrete – Spray on cement…

House6Matt writes “This stuff looks pretty incredible. To me the finished product looks a bit like an adobe building. It should greatly increase affordable housing in areas where it would have previously been too expensive.” Grancrete is a spray-on structural cement and here’s an overview of the Grancrete rapid construction process…” Link. Anyone ever use/see this in action?

16 thoughts on “Grancrete – Spray on cement…

  1. DGary says:

    Haven’t used this specific material, but the concept is pretty old, started up with the whole “earthship” movement, recycled homes, strawbale walls, that whole deal.

    We used to use a “slick-crete” type product, basically a really thin portland, sand, clay, no pebbles, and a lot of water, in kansas in the middle 80’s with my family’s farms, basically straw bales stacked up with a very light wooden frame, more for alignment than support, and spray this stuff on, we used a fertilizer flinger (a poo-flinger basically), worked good because the crete was about the same consistancy as cow-flop, and you could either spread it with a 2×4, or use a bristle broom for some texture.

    Made for very cheap sheds and could be assembled, sprayed and roofed in a day, which was great for throwing up temporary shelter for animals and tools after a tornado.

    Even better was that more than 90% of the material for it was on site, we had plenty of straw in the field, clay once we dug down a little, and water from the well, we just needed a couple bags of cement and sand.

    My uncle had figured out a way to do it without the cement, not sure of the exact mix he used but it was clay, sand, water, and I know he used straight lime in the mix, and something else, but his would breakdown after a few years, which was fine since they were just temporary and rarely lasted more than 5 years anyway without getting toppled.

  2. rolfpal says:

    I have used “Gunite” a few times. It is commonly used for ingound swimming pools and to repair structural concrete.

    The concept is that high strength concrete is used, the mix includes plasticizers and must be pumpable by a 4″ pump, usually that means that the largest aggregate is “3/8″ pea gravel”. The concrete is pumped to an applicator that also has compressed air, similar to a paint sprayer, but bigger. The concrete hardens really fast and is super strong if done right.

    I have some retaining walls in my back yard that I made from it.

    The great thing is any shape can be made


  3. asercan says:

    Grancrete itself is non-structural: the foam panels they use are reinforced and anchored to the foundation. Basically, the Grancrete protects the foam from weathering and wearing, sort of like stucco. They don’t give any details for waterproofing, but as with any stucco-like product, water wicking can be a huge problem.

    I don’t have a photo or movie of installation of Grancrete, but I have a photos and movies of Shotcrete being applied in my foundation replacement project (done by licensed professionals — this is earthquake country) here: (the movies are linked at the bottom of the page).

    Shotcrete is basically concrete, so the rebar has to be tied up before you apply it, as in ordinary construction.

  4. qwertyudotorg says:

    Check out It seems to be a superior product that can be load bearing, and a very thin application has an R40 value!

    From the site:
    *Can be made up to one-fifth the weight of concrete and maintain 1200 psi
    *Mix designs can be made up to 9,000 PSI
    *Eight (8) hour curing time versus 28 days for concrete
    *Erect houses potentially five (5) times faster than comparable masonry structures
    *Construction of homes at approximately 80% the cost of wood framed homes
    *Can be stacked up to four (4) stories high
    *Environmentally friendly – does not use wood
    *Unlike concrete, GigaCrete panels will not crack
    *Resistant to: hurricanes (Category 5), earthquake (Zone 4), fire, mildew, mold, and insects
    *Can be made bulletproof

  5. CMNetworx says:

    Here are the product Specs.. The water absorbtion is

  6. Plaster jon says:

    I have worked extensivley with grancrete in exterior installations. My background is in stucco systems. What I have found is the product doesn’t fully live up to it’s claimes. we have had problems with cracking, color fadeing and delamination. I feel there needs to be more true testing in different enviorments (not a lab). We have also encountered problems with Grancrete standing behind the product the way we feel they should. I have a 13,000 sq. ft. project that is half finished and is stalled until spring in hopes that Grancrete can figure things out. Even with the problems my self and the homeowners hope to be able to continue to work with Grancrete but if we can’t get answers form them on why we are haveing the problems we will be forced to go back to synthetic or conventional stucco. we have been consulting grancrete before and during the project to apply the material the way they suggest.

  7. Stucco guy says:

    I Managed the application of grancrete on this project under the guidance of the local grancrete and Jim Paul the co inventor of Grancrete. The project started with 13,000 sq. ft. of an old stucco system of lath,expantion joints, scratch, brown and Lahabre finish with rounded parapet top walls(sw style). In our high mountain desert area lahabre and cement finishes have a habit of spalling due to freeze and thaw conditions almost daily during the winter. We wanted to keep the look and Grancrete provided a product that claimed to have qualities that would make this possible. It was in question weather we could use Grancrete to achieve an aesthetically pleasing finish so the contract started with a synthetic top coat. After talking to Grancrete we decided to use Grancrete HFR white with color added and an antiqueing process to achieve a old world look. All of which we were told should be ok. we began by removeing all finish down to brown coat and washing the surface thoroughly. At the start everything was looking great.(we left the expantion joints in place). Half way through the project we began to notice check cracking developing 2-3 days after installation in the finish especialy in the areas exposed to the sun more. Grancrete claimed there was a mix up at the plant, the micro fibers were left out causeing the problem. We re-coated with fibered material with the same problems. As the product sat the problem magnified after prolonged expoture to the sun. but not in the areas shaded by trees. Grancrete stated that they had never seen this before and they had a new product called Grancrete PC that would work to fix the problem. We tested the product and saw similar problems but not as pronounced. The first offer from Grancrete was to provide the material to us to fix the problem at a discounted rate(the warranty clearly states complete repacement or refund). After furthure lengthy nogtiations they agreed to provide all materials and some labor money to fix the problem. By that time we were out of good weather and the PC product was not performing much better then the rest. The project is now on hold until spring in hopes that Grancrete can come up with some answers so we can finish it with their product; eventhough I am disapointed with the performance of the product and the company. I still believe this product has great potential. I would also state that any one looking to use this product they fully understand that it is extreamly difficult to finish off profesionaly. You need to be at the top of you game and have 1 key individual communicating well and directing the opperations. Also you must have a highly skilled team.

  8. Anonymous says:

    If anybody is intrested in solving the problems with respect to grancrete please send an email to We are sure of solving the problems.

Comments are closed.

Discuss this article with the rest of the community on our Discord server!

current: @adafruit - previous: MAKE, popular science, hackaday, engadget, fallon, braincraft ... howtoons, 2600...

View more articles by Phillip Torrone