Problems with Monolithic Foundations

We have avoided this topic for some time. Let’s face it, home foundations are as exciting as talking about your car’s tires. You may recall that old tire advertisement slogan, “Tires ain’t pretty!” Well, the same is true for a home’s foundation. Just like your tires, there’s a lot riding on them both.

When it comes to custom homes in Florida, there are two types of foundations – Monolithic and Stem-wall. Some folks will call the monolithic, a floating foundation, while others will call the stem-wall, a footer foundation. Regardless, here’s the quick definition of both.

  • Monolithic slabs (Photo Below) are foundation systems constructed as one single concrete pour that consists of a concrete slab with thickened portions of the slab under load bearing walls and all perimeter edges.
  • Stem-wall slabs are foundation systems constructed in three components; a footer to transfer load to the underlying soil, a masonry foundation and a poured slab.

There are some advantages of monolithic slabs. Compared to the stem-wall slab, it is faster to construct and lower in cost due to less labor being required. Yet there are some significant problems with monolithic foundations.

  • They cannot be used where you have a lot of fill dirt under the home (such as homesites where a lot of holes have been filled) because the concrete will tend to crack.
  • They cannot be used on sloping homesites because they will require a lot of concrete and become too expensive.
  • They cannot be used for homes that are required to be elevated for appearance or due to code requirements, like flood zones.
  • They tend to crack along the thickened perimeter when significant weight loads are used, like block exterior walls.

Of all these problems, it’s the cracking that should cause concern. Cracked concrete in itself isn’t a problem. It’s actually quite common. Typically control cuts are made on slabs to manage cracking. In the case of a cracked monolithic slab, the cracking along the thickened edges can become structural issues. These often ripple to other areas like drywall and flooring due to the movement in framed walls due to the cracking. In some really bad situations, this can impact the floor and truss systems.

Even with the shorter construction time and lower costs of the monolithic foundation, I recommend the stem-wall foundation all the time for our customers. Just like your tires, a solid foundation isn’t worth the risk.

Jon Solomon

www.JAVICHOMES.com

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