Slab vs Pier and Beam: What's Under Your Garland Home?

Most guides to slab vs pier and beam are written for someone about to build. They compare the cost per square foot and help you pick one.

That's not the choice most people in Garland face. Your house already stands, and its foundation was chosen the year it went up. What you really need to know is which kind you have. That decides what tends to go wrong, what a repair looks like, and the one mistake worth avoiding.

There's also a twist the building guides skip. Here, "slab" covers two quite different things. So there are really three answers: pier and beam, a slab reinforced with steel bars, and a post-tension slab held together by steel cables.

Census figures put the median Garland home at 1978. Here's how the city's 84,954 homes break down by when they were built:

• Before 1960: 11.4%
• 1960s: 15.9%
• 1970s: 27.2%
• 1980s: 20.2%
• 1990 or later: 25.3%

The Census doesn't record foundation types, so what follows is the trade's general pattern, not a fact about your address. Before 1960, pier and beam was the usual way to build in Texas. Around 1960, Texas builders moved to slabs poured on the ground and reinforced with steel bars, called rebar. Post-tension slabs spread after that. The Post-Tensioning Institute says it set out its design method for house slabs on expansive soil in 1980, and that millions of homes have been built with it since.

So if your house is from the 1950s or earlier, check for pier and beam first. A house from the 1960s most likely has a rebar slab. From 1990 on, post-tension becomes more and more likely, though it's never a sure thing.

The tricky part is the middle. Nearly half of Garland's homes, 27.2% from the 1970s and 20.2% from the 1980s, went up during the years builders were switching. For those houses, the build year alone can't tell you. The checks in the next section can.

To find your build year, look up your home on your county appraisal district's website. For most of Garland, that's the Dallas Central Appraisal District at dallascad.org, where you can search by street address. The record also has a foundation entry. That's an appraiser's note rather than an inspection, so treat it as a first clue.

You don't need tools for this, just a slow walk around the house.

If none of that settles it, there's still a safe answer. Before anyone cuts into the floor, the cables can be found with a scanner, so nobody has to guess.

A pier and beam house sits above the ground. Wooden beams carry the floor, the beams rest on piers, and a crawl space sits underneath. In many older Texas homes, those piers are short stacks of concrete block on pads near the surface. They aren't columns sunk deep into the ground.

That's why these houses move with the clay. One pier drops while its neighbor holds, and the floor between them goes out of level. The shims, the thin spacers between a pier and its beam, can also compress over the years.

The good news is access. Someone can crawl under the house and see every pier and beam, and most repairs happen right there. Shims get reset, a failed pier gets rebuilt, and rotted wood gets replaced. Nobody cuts through concrete.

The risk is the crawl space itself. Heavy clay drains slowly, so water that gets under the house tends to stay, and damp wood rots. It happens out of sight, in a space nobody visits.

So the habit worth building is simple. Have someone go under the house now and then, before the floors start telling you something's wrong, and keep the vents clear of mulch and flower beds. Our pier and beam repair page covers the work itself.

A conventional slab is one concrete pour on the ground, with a grid of steel bars inside. If your house dates from the 1960s or 1970s, this is the most likely answer.

A rebar slab is stiff. Through a dry summer, the clay at the edge of the house shrinks first, while the soil under the middle stays damp. The slab can't bend to follow it, so it cracks. How much the ground moves depends on the soil under your street, and our guide to Garland's soil shows how much that varies.

Repair usually means piers driven down beside the slab edge, then a slow lift back toward level. That work happens outside, and it doesn't cut the slab.

Inside the house, a rebar slab is the easier one to work on. If a pier is needed in the middle of the house, or a plumber has to reach a leaking drain, the crew can tunnel underneath or cut through the floor. Cutting and patching a rebar slab is routine work.

The weak spot is the plumbing. Supply and drain lines run under the slab, out of sight. A slow leak keeps one patch of clay wet, and lifting a slab can strain a line that was already weak. That's why a plumbing test before and after a lift is worth having. Our guide to the repair process shows where it fits.

Apart from those edge patches, a post-tension slab looks much like any other. Inside, steel cables run through it in plastic sleeves. Once the concrete has cured, each cable is stretched with a hydraulic jack and locked off at the slab edge. That squeezes the whole slab together, which helps it resist cracking.

The force is large. Concrete Network, a trade publication, puts a typical cable at 33,000 pounds of pull, and the cables stay under load once they're locked off.

That's why the stamp in the garage says what it says. Cutting, coring or drilling into the slab can snap a cable, releasing that force all at once. A cut cable is also hard to fix. The Post-Tensioning Institute publishes methods for splicing a damaged one, but it's specialist work, and far better avoided.

Here's the part that matters day to day. Piers set outside the house don't cut the slab, so routine pier work goes much the same on either kind. The risk comes with jobs that go through the floor:

• An interior pier in the middle of the house
• A plumber breaking out the floor to reach a leak
• A remodel that moves a toilet, sink or shower drain
• Bolting a car lift or a heavy safe to the garage floor

Before any of those, the cables should be found with a scanner first, or the crew can tunnel underneath instead. A good contractor will bring this up without being asked. If one doesn't, it's a fair thing to raise.

Everyday living never touches the cables. The warning is about cutting, coring or drilling into the concrete itself.

The type of foundation on its own isn't a reason to walk away. What matters is the condition of that particular house, and the type tells you where to look.

A seller who has those answers ready is telling you something good. And if you'd like a second pair of eyes before you buy, a free foundation inspection covers the floor readings and the crawl space.