Free white paper
Why Did My 1980’s Slab Crack?
Pull up the old carpet in a house built in the 1980s and you may find a crack running through the concrete slab. It is common, and it usually traces back to how the slab was reinforced when it was placed. This white paper explains what went wrong then, what a correctly reinforced slab looks like, and what to put in writing before anyone pours concrete for you. The same ideas apply to driveways and patios.
What the paper covers
- Why the hog wire used in older slabs often did nothing at all, and what “hooking” was
- Where steel actually belongs: two inches from the surface and two inches from the dirt in a four inch slab
- Rebar laid in a mesh pattern, spaced no more than 12 inches apart and tied at every intersection
- Rebar chairs, the inexpensive blocks that hold steel off the ground, and why to name them in your contract
- Control joints no more than 10 feet apart, so cracks land where you decide rather than where they like
- Why concrete mixed with fiberglass fibers is not a substitute for rebar
Written by Philippe Heller, who founded The Real Estate Inspection Company in 2004. 11 page PDF.
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Why we wrote it
Most of the cracked slabs and crumbling driveways we find on inspections are not mysteries. They were placed with no reinforcement at all, or with reinforcement that ended up sitting under the concrete instead of in the middle of it, where it would have done some good. None of that can be corrected once the concrete is down, which is why it is worth knowing before you hire anyone for your next project.
Check with your local building department before you start. Requirements vary from one jurisdiction to the next.