Building a Concrete Slab to Last Forever

BUILDING A CONCRETE SLAB TO LAST FOREVER, AT THE OFF-GRID HOMESTEAD

Can something we build today, using the materials and techniques available, last forever? Like the ancient Pyramids and Temples in the world?
With a focus on durable materials, solid soil, and proven best practices of construction, I believe it is absolutely possible to build something that resists failure from either human-made or natural events.
Here is a way to build a concrete slab, that we believe will last forever. Similarly, all other buildings at the off-grid homestead, and each of these buildings’ components, will be built to last forever.
At the off-grid homestead in North Carolina, we have finished four out of five concrete slabs. The two smaller ones you see in the photo of the residence portion of the project, is covered with a concrete slab protection membrane that I’ll get to later in this post.
concrete slab durability building science lg squared concrete slab durability building science lg squared
First, I want to talk about how we built these concrete slabs, and why we think these things are going to be around forever.
We started off with a really solid soil base.
concrete slab durability building science lg squared
Wherever we found loose or not well compacted soil we pulled it out and replaced it with some other good soil from somewhere from other parts of this property.
concrete slab durability building science lg squared
Once that was really well compacted we dug the trenches for the turn-down portion of each concrete slab.
concrete slab durability building science lg squared
concrete slab durability building science lg squared
Next, we installed four (4″) inches of insulation at the bottom of the turn down, four (4″) inches of insulation on the inside and turned that four (4″) inches underneath the concrete slab, for two feet and then transition to two inches for the remainder of the interior of the concrete slab.
once that was really well compacted we dug our trenches for our the turn-down portion of our slabs
once that was really well compacted we dug our trenches for our the turn-down portion of our slabs
once that was really well compacted we dug our trenches for our the turn-down portion of our slabs
The reason we beefing up the exterior the the edge of the concrete slab is because most of the heat loss in the concrete slab happens at that exterior and mostly in that horizontal direction because the coldest temperatures will be just outside the edge of that slab.
In addition to the insulation on the bottom and inside edge of the turn-down, we will be installing six (6″) inches on the outside of the concrete slab. Once we remove the form-work from the edge of the concrete slab, we will attach six inches of rock wool insulation, continuously to the entire edge, and then we will continue that insulation up to where we turn to the roof, where we will install eight (8″) inches of insulation on top of the roof structure, outside of the sheathing layer.
concrete slab durability building science lg squared
Again, all of the insulation from all buildings here at the off-grid homestead is going to be on the outside of the structure. That includes the framing, the sheathing and everything else that’s a part of the structure. The entire structure is going to be inside a nice warm “blanket”, or “sweater” of durable, rock wool insulation.
insulation slab durability building science lg squared
Between four (4″) inches to eight (8″) inches of rock wall insulation, or in the case of the bottom of the turn-down portion of the concrete slab, EPS (Extruded Polystyrene), will cover the entire structure, helping preserve it, forever.
The next thing we do is install a 15 mil vapor barrier on top of the insulation covering the entire portion under the concrete slab and on all sides of the entire turn down, including up the edge to the top of the concrete slab.
vapor barrier slab durability building science lg squared
vapor barrier slab durability building science lg squared
vapor barrier slab durability building science lg squared
All of the seams are overlapped and sealed really well with a tape that we that’s been tested with that vapor barrier to ensure a tight seal and any penetrations through that vapor barrier like a plumbing pipe or electrical conduit is also wrapped with more vapor barrier and then sealed again with that tape this vapor barrier prevents moisture from below getting into the concrete slab and then into the house.
vapor barrier slab durability building science lg squared
vapor barrier slab durability building science lg squared
Once we have the concrete slab poured we have to protect it so we don’t lose moisture really quickly and especially when you’re pouring in summer or late summer it can get up to 80 90 degrees, and that would suck the moisture right out of the concrete, if left exposed.
slab protection durability building science lg squared
Immediately after we finished pouring the concrete slab we installed a floor protection membrane over the entire concrete slab. Although the material is designed, and manufactured, as a floor protection system, we selected the non-perforated version to help us with the curing process, as well.
slab protection durability building science lg squared
slab protection durability building science lg squared
slab protection durability building science lg squared
To building a concrete slab to last forever, we must keep the moisture in the concrete as long as possible during construction, to allow it to cure. In the case of the off-grid homestead, we are going to allow these slabs to cure for three to four weeks before we start framing, or any other construction activity. Even when we do start working on the slab, again, in 3-4 weeks, the membrane will continue to keep that moisture in the concrete, allowing it to continue its slow curing process.
slab protection durability building science lg squared
As soon as these the finishers left the job site, we installed the membrane on the slabs, securing them to the form work. Once the form work is removed, we will attach the membrane to the edge of the concrete slab with a tape that has been proven to adheres to the concrete. We will still spray some adhesive primer on the concrete, before we secure the tape to make sure we get a good solid bond that’s gonna last throughout construction.
Once once we’re done with all the framing and the finish work inside the house we’re gonna come we’re gonna come back and cut right along the base that the bottom plate of the framing and be able to remove all of this this product here and once we do that then we can get in with our finisher for the concrete slab because the concrete will be the final finish. Some sort of protection is absolutely necessary in order to have have a beautiful finish, in addition to asking all of your subs to be extremely careful while they’re working. The protection membrane is for accidents and the unavoidable foot traffic, because both happen. You cannot avoid walking on these slabs
Especially with the red clay here in Western North Carolina, if it ever gets moist or muddy, we would have red footprints throughout the concrete slab. So, this is going this is gonna eliminate that, accidental spills, and scratching that occurs through the construction. AND…it helps the concrete cure!
concrete slab durability building science lg squared
We’re gonna have a beautiful finished concrete floor when we were done and thanks to everything we’re doing to make these concrete slabs last forever we’re really confident that these they will be strong and sturdy for the duration of these owners lifetime and many generations to come.

Project Info:
Architect: LG Squared, Inc – http://www.lgsquaredinc.com 
Builder (GC): LG Squared, Inc – http://www.lgsquaredinc.com   
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Manufacturers of products used:
– Rock Wool Insulation: https://www.roxul.com
– EPS Insulation: https://www.insulfoam.com/, a subsidiary of https://www.carlislesyntec.com/   – – Vapor Barrier: https://www.wrmeadows.com
– Floor Protection: http://www.kleenwrap.com/

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