Foundations: Pier & Beam vs Pier-ed Slab. Which is Better?

Remember that freeze we had just before Christmas last?  Somehow, something had knocked the insulation off a fire sprinkler pipe in the attic above our media room, which took talent because we have a ton of insulation in our attics. Since I seldom go upstairs, I did not know there was a leak from a frozen fire sprinkler that burst once it thawed, filling the room like a swimming pool. When I opened the door to the garage, directly below this room, it was Niagara Falls!

A whole lot of clean up, drying, hauling, moving, and wall/floor repair later, I am learning first hand the difference between two foundations, the post tension slab and old-fashioned pier and beam. 

First off I consulted one of my trusty Candy’s Dirt-approved homebuilders, Tony Visconti of Bella Custom Homes. Tony builds multi-million dollar estates, huge ones, such as his glorious home on Deloache. The available home at 4926 Deloache in Old Preston Hollow is a pier and beam foundation with a basement. This home is a little over 14,000 square feet of luxurious finish out, all situated on a gorgeous, wooded 1.76 acre lot.  

Which foundation is better, I asked?

“Any engineered foundation is great,” said Tony, “as long as it is engineered for the plasticity in the soil on your specific lot.”

Which is why Tony, like every fine custom home builder should, has a geotechnical engineer on call for his projects. Tony uses Henley Johnston and Associates to do soil testing on all of his lots. They should be the first date your lot has. Once your engineer has the soil report in hand, he sends that off to his structural engineers at Paragon Structural Engineering.

“They see how expansive the soil is, and check for the potential vertical rise,” says Tony.

And then they design the foundation and framing, based on the findings. They also discuss with the builder what foundation they recommend for the soil: pier and beam or the post tension slab with piers.  The type of foundation that Bella Custom Homes uses depends on each lot’s site conditions, along with the clients’ budget.

Pier and beam slabs are more expensive to build, $10 to $15 more per square foot: they require more labor and materials. They also require small cut-outs and small crawl spaces under the house for ventilation, future servicing and repairs, and also future remodels. But they also leave pipes more susceptible to freezes.

I told Tony that I always detect a slight musty odor in older pier and beam homes, often ranches, and he agreed: water can sometimes pool under the house. You remove it with a sump pump.

With a post tension slab with piers, there is no space between the concrete and the dirt; the foundation sits right on top of it. This in turn does protect your pipes from freezing, but in the case that one does freeze, then it is a more costly repair. The pier and beam repairs will cost less to make. In my home, there is the engineered slab, the moisture barrier, plywood, felt, and the oak hardwood floor.

But as we have discovered, if a pipe breaks, you cannot easily get below the slab or the hardwoods to repair it, as you can with a pier and beam foundation. Pier and beams also make remodeling and additions to the home easier.

“All foundations also require an irrigation system around the house,” says Tony, “to keep the ground saturated in the summertime when it’s dry.”

If the slab saves you money when building, it will not save you much when your floors are saturated with water. I didn’t know water from the fire sprinkler leak had seeped below my first-level floors, flowing down the walls. I didn’t know this until my wood floors “cupped” and buckled, the joints of the wood becoming little ski jumps at doorway junctions. The floors even turned white, which was actually kind of pretty: the water was creating calcification in the wood.

But they had to come out. So we are now living on a slab, having torn up the oak hardwoods I meticulously maintained and vacuumed after every dinner party.  New ones will be installed once the slab dries.  All of which makes me wonder if I would forgo the slab in my next house and opt for the pier and beam we have had in every other home we have owned. What do you think?

by Candy Evans of the FABULOUS Candy's Dirty!