The process of pouring concrete over rigid foam insulation varies depending on the type of insulation used. Foam board insulation is a lightweight, cost-effective alternative to fiberglass batts due to its ability to spread load and not require a protective barrier. It is installed on top of concrete pads and subfloors to insulate new floors above them, such as wooden decks or concrete pads.
For existing slabs, there are no perfect materials for covering and protecting exterior foam on foundations. Metal or plastic reinforcing can be used to strengthen cement parging on the foam board panel, flush against the waterproofing membrane. Phenolic foam is a popular choice for achieving strong levels of insulation for less depth.
Foam insulation is designed with a loading value per unit area, and as long as this loading is not exceeded, it will not deform. To ensure proper pouring, the concrete should be in direct contact with the vapor barrier, as the foam has a better chance of drying and staying dry underneath the sealed surface. Staggering joints and tacking the foam into the ply can help hold everything together for the pour.
The foam board (2″) supports the weight of the concrete, worker, and wheelbarrow, as radiant heat is typically added to high-end concrete. However, it is essential to place a vapor barrier on top of the foam to prevent “iceberging” and pour concrete directly on insulation. Insulation is a soft and lightweight material that is not designed to support the weight of concrete.
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Do you need a vapor barrier between concrete and insulation?
Moisture build-up in a basement is a common issue, and proper basement insulation, moisture barriers, and wall sealants can help prevent condensation and damage to the building. When building a new house or repairing a basement, it is most effective to run a moisture barrier directly in the structure. Place vapor barriers on foundation walls before installing posts and primary insulation. Proper use of basement insulation, moisture barriers, and wall sealants can keep the basement dry and safe.
Melt is always present in modern homes, including water in the ground, condensation, dampness, and moisture from stoves or showers. To waterproof a basement, more than just concrete is needed. Water vapor can pass through the concrete from the subsurface or indoor air, and can condense if it passes through walls, ceilings, or other obstructions. A vapor barrier is a material used to prevent water vapor from penetrating a wall, ceiling, or floor during cold winters.
The intelligent vapor barrier adapts to wick moisture away from the wall, regardless of humidity levels outside or inside the wall. Drywall or green foil is not resistant to moisture trapped in the barrier.
How long does foam last under concrete?
Foam jacking is a more efficient and cost-effective method for repairing sunken concrete slabs. It is more durable, able to withstand heavy loads and foot traffic, and won’t erode like mudjacking. The foam material can be controlled more easily, allowing for a more precise injection rate based on the extent of the sunken area. Foam jacking can last 20 years or longer, making it a more reliable and cost-effective option for homeowners and contractors.
The cost of foam jacking depends on factors such as the severity and size of the damage, the amount of foam needed to fill the voids, and the project’s location. On average, foam jacking costs range from $10 to $25 per square foot. This makes it a more reliable and cost-effective option for homeowners and contractors seeking a long-term solution to their concrete problems.
How to secure foam board to concrete?
Attaching foamboard to block or concrete walls is typically done using a mechanical fastener like a masonry nail or screw. This is because the weight of foamboard can put pressure on sealants and adhesives, slowing down the project. A masonry drill bit and screw with a washer tends to go faster than adhesives. However, butyl tape can be used to temporarily secure foamboard and vapor barrier installation, and is recommended over adhesives for foam board installation. This method is particularly useful for rimjoist and rim-joist sill plate insulation.
Can you concrete over expanding foam?
Expanding foam is a fast and cost-effective solution for concrete sinkage. It can be used in just 15 minutes, unlike mudjacked concrete which takes at least 24 hours to dry. Expanding foam requires only small holes to pump under the slab, eliminating the need for heavy excavation. It is lightweight, weighing only 2. 5 to 4 pounds per cubic foot, which supports the slab without adding extra weight to the soil. It is also non-toxic, meaning it won’t leech chemicals into the grass or soil.
Expanding foam is cost-effective, as it lasts indefinitely, eliminating the need for repeated mudjacking and slab replacement. It is also waterproof, as the polyurethane won’t wash away when it comes in contact with water. However, experts recommend correcting drainage issues that cause water to flow towards the concrete slab. The average cost of expanding foam depends on the type of slab needed, with sidewalks starting around $800 and driveways, patios, and interior slabs starting around $1, 500.
DIY concrete leveling is not recommended due to the need for special equipment and the availability of tools and machinery. Most foundation repair experts also provide concrete leveling services, such as The Real Seal.
How thick should concrete be over insulation?
The final floor level refers to the uppermost surface of a floor after construction is complete but before any finishes are applied. It is advisable to have a minimum of 100mm insulation covered with 60-80mm screed. Greater screed thickness may lead to a colder floor. The best example of insulated floor thickness is 100mm (insulation) + 60mm (screed) + 20mm (floor tiles+adhesive).
A damp-proof membrane (DPM) is typically used in floors to prevent moisture transmission. It is recommended to lay the DPM underneath the insulation to prevent capillary action of water. Insulation should be laid above the DPM to prevent moisture degradation over time. The DPM should be flat and not torn during installation. The DPM should be black and be a suitable thickness for the floor.
Does construction adhesive work on foam?
Great Stuff™ Construction Adhesive is a moisture-cured adhesive designed to bond various construction materials, including subfloors, drywall, paneling, and foam panels. While it can be used outdoors, it discolors if exposed to UV light and eventually crumbles. To remove the foam from the skin, use fingernail polish remover, a polyglycol-based skin cleanser, or corn oil, then wash with soap and water. If the foam has hardened, no solvent can be used, and it will wear off over time. To remove cured foam, use a pumice stone and warm, soapy water, then apply petroleum jelly.
Should you put foam under a concrete slab?
Concrete slab insulation is crucial for maintaining indoor temperatures, controlling moisture, improving energy efficiency, and saving energy bills. Common forms include rigid foam insulation like expanded polystyrene (EPS), extruded polystyrene, and Polyisocyanurate (Polyiso). EPS, also known as beadboard, is a lightweight, rigid, closed-cell foam made from tiny polystyrene beads that undergo a process of softening, expanding, mold, and fusion using thermoplastic polystyrene.
What is the best adhesive for foam to concrete?
3M 78 Polystyrene Foam Insulation Spray Adhesive is a quick-drying, specifically designed for insulation foam. It doesn’t eat away at the foam, making it the best spray adhesive for foam board. Other options include 3M Foam Fast 74 Spray Adhesive Clear, which bonds foam board to various materials like cardboard, paper, insulation, metal, plastic, and wood. 3M 90-24 Hi-Strength 90 Spray Adhesive is particularly effective for adhering fabric and foam, making it the best adhesive for foam board to concrete.
Will concrete bond to spray foam?
Spray foam insulation can be installed on old concrete, provided it doesn’t have residue that could hinder adhesion. This insulation helps control temperature changes from the building’s root. Open cell spray foam is not suitable for stones and underslab due to its inability to handle moisture below-grade applications. Its sponge-like texture makes it prone to absorbing water, making it not suitable for these applications.
Does great stuff foam adhere to concrete?
The adhesive formulation of the GREAT STUFF PRO™ Construction Adhesive exhibits versatile adhesion capabilities, rendering it compatible with an array of materials, including rigid foam insulation, lumber, plywood, particleboard, masonry, drywall, and concrete. This adaptability reduces the necessity for additional fasteners, thereby streamlining the construction process.
Does concrete adhere to foam?
The results of the 120 tensile bond tests and 30 shear tests on concrete-rigid foam composites indicate that the application of concrete onto rigid foam can result in the attainment of technically relevant bond strengths.
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I have raised many slabs with foam and jacking equipment. Was thinking about trying this just never had the time. The foam should hold due to he used the right type. It may come down eventually but that would be due to erosion which cannot be controlled except with other types of erosion control. Comment about cutting loose is a good idea to.
I luckily ran out of cans of foam when trying to lift a 36 inch by 50 inch sidewalk slab. I put 2 C-clamps on the side facing my front lawn, attached chains to a 6×6 beam and bottle jacked the beam/slab up 1.5 inches to match the the other slabs. I could not grab any other sides as they were hemmed in by the curb/other slabs. The curb side was still down an inch. I drilled 9 holes and started filling the curb side first, I think that was a mistake as the foam had plenty of space to expand towards the lifted side and the curb end did not seem to be lifting. I then started to fill the holes on the lifted end to dam up that end. I used all 6 cans of foam (Great Stuff Wide Gap Exterior) that I had and ran out to the hardware store. When I returned 25 minutes later the whole slab had lifted up a little too much. (evenly) I was lucky I ran out or I would have kept pumping foam in there and I would have raised the slab up way too much. I had to raise one of the adjacent slabs a little bit to even it out, I only drilled 3 holes and did not use the bottle jacks on the adjacent slab. In general I am happy with the project but be careful not to over do the foam as it continued to lift for a half hour or so.
I’ve used it where if you can pry up a sunken section to level then, you can spray foam the void, once solidified remove pry wedge… also same as in article not with the intention of lifting the slab but filling in the void under the slab where the gravel/pebble/sand has washed away over the years. The spray foam will stop further settling sometimes that’s the only option if you can not manual pry the section to level.
I had this idea re: great stuff but wasn’t sure if it would work ..thanks for articleing how to do it & that it does indeed work! Need to lift a sunken concrete slab on 1 end in my backyard that some contractor gave me a usurious estimate ( over $1100.) to break up & replace the 1 slab that is otherwise intact & stable .glad I you tube-googled slab jacking . I wasn’t sure could be done & found this article in particular.you helped old lady get smarter.
10 cans Great Stuff? Basically trying polyjacking but doesn’t address the continued sinking of the ground below, so will be sinking again. Probably wasn’t built over solid base, sand, packed road base deep enough. Also water flow issues and clay soils in NW Ohio expansion, shrinkage, freezing repeated cycles…needs a base under the concrete that can flex with the freeze- thaw cycles or just expect this repair to be needed at least annually…
I tried this on a 36′ wide walk way. used 4 cans till it was squirting back out of the holes, and I had the holes pressure sealed pretty good while squirting it in. It really didn’t do any good, maybe 1/16th ” rise. $ down the drain.Now I will try another area.I drilled the holes. Now I’m wondering if the slab might be more likely to lift if I put water down the holes and let it get damp over night. Wondering if that might help to break the tight seal between the concrete and the dirt underneath.
good idea, just be mindful that the foam may be open cell and will absorb moisture and eventually breakdown contaminating the soil. I use a closed cell that will not leach over time. For the 12 cans ($144) used to get a partial lift a professional could achieve entire project for same price. Be sure to fill voids away from joint to support slab and prevent crack in future.