What's the Difference? | Slab Foundation Comparison
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- Опубліковано 9 лют 2025
- Learn about what makes a stem wall slab foundation different from a monolithic slab foudation!
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You mentioned putting the insulation around the edges to prevent heat loss. What about heat loss from the middle of the slab going down into that 60° soil? How does that work or not work? Thanks
Great question Kevin! In climate zone 3, we are cooling dominated, so the stable ground temperature beneath the middle of the slab actually helps to reduce the cooling load on the home. While it is a slight penalty in the heating season, its reduction in cooling load more than compensates for this. We could certainly add continuous insulation under the entire slab, but the perimeter approach is a great balance of cost and effectiveness.
In this system, if you do not have ground water 8 feet below all the soil down there works as an insulation. Such practice is very common in countries with cold climates
Do you insulate under the entire slab or just perimeter and stem wall? Was curious as well, appeared to be drop off behind you, combination crawl and slab or fill to allow for slab through out? Appreciate good basic info at an affordable level.
Thanks for the questions! In our climate zone, we only insulate the perimeter and stem wall to reduce the perimeter thermal break. We actually gain benefit from the stable ground temperature beneath the slab which helps to reduce our cooling loads in the summer.
The stemwall slab in this video was taller on one end due to the variation in topography and was filled to be slab for the entire foundation.
Setting aside cost, wouldn't it be beneficial to tie the slab to the stem wall with rebar, ie, have some angled rebar coming out of that bottom course of block and tying into the rebar grid on the slab?
There are really no benefits to tying the slab to the stem wall if everything is constructed on sound subgrade. If you brought the rebar out of the bottom course of block, it would be near impossible to insulate the perimeter of the slab.
How would you finish the exterior of a stem wall and does it not need insulation?
A stem wall can be constructed with a brick exterior, stone exterior, or a stucco/parge finish. On most of our stemwall foundations, we parge the exterior to create a stucco look and paint it with elastomeric paint.
How did you put the anchors in? Didn’t see any wet set into the 4” blocks.
We use Simpson Titen HD anchors after framing. Much easier to locate these where you want them to go.
Curious as well as to experience with Superior Wall. In your intro I believe it makes a cameo being installed. Was that a customer one time or you find it to be an effective sub for block or powered foundations when doing full basement.
Hi Kevin! We have been using Superior Walls for our basement foundations for 20 years. I absolutely love the product and we find it to be more cost competitive than poured concrete walls in our market. We don't build block basements. Our clients receive a lifetime warranty from Superior Walls on their basement system covering structural and moisture infiltration and the system provides a waterproof, insulated, and ready to finish system. Happy to discuss further if you're considering using the product.
What if you want the foundation to have a brick facade instead of block?
Not a problem at all, you simply construct a double wythe brick wall where the inner wythe of brick becomes the ledge as the 8" block does in this video.
How does what you explain differ from Florida
This type of slab can easily be installed in Florida, although most Florida slabs that I have seen are monolithic slabs.
Why do you need to insulate the perimeter of a monolithic slab? Sounds like a straw man argument to me. Monolithic slabs are extremely formidable against all assailants. I come from Texas. Monolithic slabs are were almost all we knew.
In our climate zone, and in most zones covering Texas, the energy code doesn't require the perimeter of a slab to be insulated. However, concrete is a fantastic conductor of heat and without a perimeter thermal break (insulation), heat will move out of the slab edges in cold weather, resulting in energy loss and potential comfort issues. Concrete is definitely not formidable against heat movement. In colder climates, insulation is required by code. Hope this helps!
Silly Texans. Jk north west Arkansas here. We insulate under slab here. Helps a ton in winter but does hurt in summer. Closed cell helps most