Concrete slap vs pier and beam foundation (hardwood floors, dehumidifier, air conditioning)

[Nn2036]

What is the pros and cons of concrete slab and pier and beam foundation? These are the only 2 I know of, any other type available?

My 2 houses I lived previously, one is concrete slap and one is pier and beam. My area is clay rich and very hot in the summer. And I was told to water my slap foundation frequently or it would shift and causing cracks

[TrapperL]

Well, it's a slab, not a slap. There are several different types of slab foundations, Post Tension probably the most frequent these days with a steel slab second. For high clay soils and wanting a residential slab foundation, the post tension allows the foundation to flex and move around without breaking. We primarily use the Post Tension or cable slabs here due to our high clay soils. The steel slabs will be the most expensive but are prone to break in high clay soils as they don't flex much. Most commonly around here a commercial slab will be steel but have a raised compacted fill of PI 17 or less and at least 18" thick. This gives the slab drainage and a good base to rest on. The cost of the steel is what makes them too expensive for residential use. Pier and Beam are the most stable in high clay soils but they can be expensive versus a Post Tension. Piers may extend down 30 feet or more around here to reach stable soil. That costs money to drill, steel for structural support, pouring into sonotubes, and then the beamage poured. Build time is longer but it is the most stable, trouble free, and permanent.

With our high clay soil content, builders will have in their closing papers documents that you will sign making you aware that you must water the foundation to keep the soil damp under the house. Of course they don't seal the slab to keep the air conditioning from sucking the moisture out from under it. And then we also have water rationing here which makes it almost impossible to put enough water around the house with a hose the one day a week and for the 4 hours you're allowed to water. So the home owner here doesn't stand much of a chance. I guess that's why our Yellow Pages are full of foundation companies. On average, if a foundation needs a full set of piers installed under the home, you'll spend close to 40 grand for them. Bigger houses will be more money. The biggest scam here though with the foundation companies is with their warranties. They will warrant their work on a partial set of piers until the foundation needs the rest of the house leveled with piers. Once somebody else comes along and installs piers, the original warranty is void. So folks end up with foundations that are still moving around, spent huge amounts of money, and have no warranty. Make sure to read and understand the warranty being offered with any piers or pier and beam foundation. If you have a slab that needs work and piers, have it all done or none of it. You'll thank me later.

[southernnaturelover]

I prefer a slab foundation, but our soil here is mostly sandy loam. Here in the Deep South, the high humidity causes mold and musty smells in crawlspaces, even with a vapor barrier. Some people use unvented crawlspaces with a dehumidifier, but that's just wasted electricity and more maintenance IMO. If you have a toilet leak or a clogged a/c drain line, it can be disastrous if you don't catch it right away. A slab house just feels more solid, no floor bouncing when using a treadmill.

Also, as you get older and your knees get worse, a slab house only has one little step to get inside. The only downside to a slab, is if you have a drain pipe break, it may require jackhammering up part of the floor, but that's rare. With a slab it is more important to keep aggressive tree roots away from the foundation.

[Nn2036]

Originally Posted by TrapperL

With our high clay soil content, builders will have in their closing papers documents that you will sign making you aware that you must water the foundation to keep the soil damp under the house. Of course they don't seal the slab to keep the air conditioning from sucking the moisture out from under it. And then we also have water rationing here which makes it almost impossible to put enough water around the house with a hose the one day a week and for the 4 hours you're allowed to water. So the home owner here doesn't stand much of a chance. I guess that's why our Yellow Pages are full of foundation companies.

Thanks! So what is the type of slab that the builder usually put in for the standard house?

What is the construction of pier and beam besides cost? What happened to the crawl space when it rains? Does it get flood?

[KathrynAragon]

Originally Posted by Nn2036

Thanks! So what is the type of slab that the builder usually put in for the standard house?

What is the construction of pier and beam besides cost? What happened to the crawl space when it rains? Does it get flood?

Each foundation type has pros and cons but both are generally sound choices to make. Of course there are rare exceptions but generally speaking, either foundation type can be built well and can stand the test of time.

I have had both types - on older homes and on new construction. My house prior to this one was built on basically a clay hill, in Texas, so you can imagine how hot it could get. Within a year there were hairline fractures through the garage and I'm sure they extended into the foundation of the home itself. Hairline fractures are not structural issues but let's just say I wasn't comfortable with that at ALL. We were also in a drought and had water rationing going on so how was I supposed to keep this foundation "watered?"

Anyway, we sold that house (no problems with the inspection) a few years later and bought a house that is NOT built on clay, that is also 20 years old, on a slab foundation. Not only were no hairline fractures in the garage or any part of the foundation that we could see during an inspection, we had all the flooring pulled up and replaced when we bought it, and there was not a single ripple or fracture in that beautiful slab foundation. Once again - lots of heat in Texas summers - for 20 years with no issues. I feel great about the integrity of this slab foundation.

But I have also owned several older pier and beam houses and actually I prefer the "feel" and the convenience of pier and beam homes. For starters, if you need to replace or repair any pipes, it's a piece of cake, and as a home ages, repairs are a part of life, though those repairs shouldn't come for many years. But it's not just that - for instance, we wanted to convert a fifth bedroom in one home I owned into a big laundry room, which meant installing pipes beneath that floor. It was very simple to do in a pier and beam home - and inexpensive.

In another pier and beam home I owned, there was a foundation problem, but guess what - it was easily fixed, for about $3000, and it was a pretty significant repair that had to be done. I felt like that was not a huge expense on a 50 year old foundation and was happy to get it completely and easily repaired. Repairing a slab foundation is a huge ordeal, and in Texas that repair must always be disclosed in future sales and it generally lowers the property value, even if the repair is guaranteed to be sound. Not the case with a pier and beam foundation which is usually much easier to repair if necessary.

As for flooding, that was actually what caused the issue in the pier and beam foundation I was just describing. A neighbor had built some sort of retaining wall or something that had routed water toward my house (the house I was buying anyway). No one knew this would create a problem but it did. Water had weakened a section of the piers and beams on one corner of the house. All that was required was for that small section of piers and beams to be replaced (not difficult) and for the water to be rerouted, which was also not difficult. Like I said, the total cost was $3000 and it was 100 percent repaired.

So yes, with a pier and beam foundation, you do need to be sure that water is routed away from the house. That isn't particularly difficult to do - you'd need to do that regardless of the type of foundation you choose.

I have had ankle surgery and one thing I can tell you is this - pier and beam floors have a bit more "give" to them than concrete slabs do. Many homes on pier and beam have hardwood floors. This combo is a lot easier on the ankles and knees over time than flooring on a concrete slab. But I don't really think that generally speaking, this is something you need to over analyze or use as a major factor in a decision. It's just something to consider.

Hope that helps.