Sloping, bouncy floors in an older Dallas house: what is happening in the crawl space

What is usually going on under an older floor

In an older pier-and-beam house, sloping or bouncy floors almost always come from what is underneath: piers that have settled into the clay, wood shims that have crushed or rotted, and beams that have sagged or softened from crawl-space moisture. The fix is usually re-shimming and re-leveling the floor, replacing piers that have failed, and repairing or sistering damaged beams, done from inside the crawl space, along with whatever drainage work keeps the space dry. It is a different repair from a slab, and often a gentler one.

I evaluate foundations for FCS Foundation & Concrete, and a large share of the older houses I see in East Dallas, Oak Cliff, Kessler Park, Lakewood, the M-Streets and along Swiss Avenue sit on pier-and-beam. Our page on historical homes puts it simply: most of the area's older and historic houses sit on pier-and-beam foundations over a crawl space. This guide explains how those foundations age, what the signs mean and how a careful repair works.

How a pier-and-beam foundation is built

Instead of a concrete slab poured on the ground, a pier-and-beam house sits on a raised wood floor. Piers, short columns set on pads in the soil, carry beams that run under the house. Joists span between the beams and carry the floor. Between the top of each pier and the beam above it there are usually shims, the adjustable layer that sets the floor height.

That design has real advantages. Plumbing and wiring under the floor can be reached from the crawl space, and the floor can be adjusted without breaking concrete. But it also means the house is resting on many separate points, and each one can move on its own.

It also means the problems are usually local. One settled pier under a hallway produces a dip you can feel in that hallway and nowhere else. A row of crushed shims along one beam makes one side of a room slope. That is why the repair is often a matter of adjusting and replacing specific supports rather than lifting the whole house at once.

Why these floors drift over the decades

Our historical homes page describes the pattern after 60 to 100 years or more of wet-dry clay cycling: original piers settle, shims crush, and beams sag or rot. The clay under each pier swells and shrinks with the seasons, and piers near the perimeter tend to move more than those in the center because the soil at the edge of the house dries and re-wets the most.

Moisture in the crawl space is the other half of the story. Wet soil under the house makes pads settle, and damp air keeps beams and joists wet. Wood that stays wet softens and rots early, and a softened beam sags between the piers even if the piers have not moved at all. Poor grading or a downspout that drains toward the house can leave standing water under the floor after every rain.

• Piers that have settled into the clay, especially around the perimeter
• Wood shims that have crushed, shifted or rotted
• Beams sagging between piers, or softened by rot
• Standing water or damp soil in the crawl space
• Earlier repairs that stacked loose shims without fixing the cause

Signs worth a closer look

Older houses tend to show trouble early. The original doors and windows, plaster walls and trim all react to small movements, so you often notice something long before the problem is serious. These are the signs our historical homes page lists, and they match what I see.

A musty smell is the sign homeowners most often dismiss. Damp air from a wet crawl space rises into the house, and the same moisture that causes the smell is what rots beams. If the smell comes with visible mold or a stain inside, an environmental inspector's view of where the water is coming from is in this guide to musty smells and ceiling stains.

• Floors that slope, sag or feel bouncy underfoot
• Trim separating from walls and cracks in plaster
• Original doors and windows that stick or will not latch
• Piers or beams in the crawl space that look settled, tilted or rotted
• Cracks in the masonry or brick
• A musty or damp smell coming from below the floor

A look in the crawl space you can do yourself

If you can safely reach the crawl space access, a flashlight look tells you a lot. You are not diagnosing, just gathering notes for whoever evaluates the house. Look for standing water or mud, a white bloom or dark staining on the wood, beams that visibly dip between piers, and shims that are crushed, split or stacked several deep. Note any piers that lean. Photograph what you see.

Do not crawl in if the space is flooded, tight enough that you could get stuck, or shows signs of animals or exposed wiring. A professional can do it safely, and the photos from a quick look at the access opening are still useful. Outside, check where downspouts discharge and whether the soil slopes toward the vents. Water that runs toward the house in a storm usually ends up underneath it.

How a careful pier-and-beam repair works

Older houses need a careful hand. Our historical homes page says it directly: original longleaf pine, hand-laid brick and plaster walls cannot be replaced at any price, so we do not treat a historic house like a tract home. That shapes every step. We lift gently and in small increments, working from the crawl space wherever possible, so plaster and masonry have time to adjust instead of cracking.

Our historical homes work takes us to Munger Place, Swiss Avenue and Junius Heights in Dallas, the older streets of Richardson, downtown Carrollton and Fairmount in Fort Worth. In houses like these, the floor system is often original, and earlier owners may have added piers, posts or stacks of shims over the decades. Part of my job under the floor is sorting out which supports are doing real work and which are leftovers. If your house is in a historic district and the plan involves any exterior changes, check with your city about what review applies before the work is scheduled.

The work follows the evaluation. I take elevations across the floors, inspect the piers, shims and beams from below, and identify what has moved and why. The plan then combines whichever of these the house needs. The same crews also repair slabs, so a later slab addition on an older house can be handled in the same plan.

• Re-shimming and re-leveling the floor system with solid, properly sized shims
• Replacing piers that have settled or failed
• Repairing or sistering beams that have sagged or rotted
• Correcting drainage so water stops reaching the crawl space
• Re-measuring the floor to confirm the result

Drying out the crawl space so the repair lasts

Leveling a floor over a wet crawl space treats the symptom. If water keeps reaching the soil under the piers and the beams stay damp, the house drifts again. For houses where moisture is the driver, we encapsulate the crawl space: a heavy-duty vapor barrier over the ground and up the walls, sealed at seams and piers, with vents, penetrations and rim gaps sealed and a crawl-space-rated dehumidifier keeping humidity down. Where water actually enters, drainage or a sump comes first.

Our crawl space page describes the benefits as drier beams and joists, less mold and musty air rising into the house, slower moisture-driven soil movement under the piers, fewer pests and lower humid air for the air conditioning to fight. A typical encapsulation project takes one to three days, and the crew checks humidity readings before leaving. Drainage outside matters just as much, and the basics you can handle yourself are in my guide to watering and drainage around the foundation.

What it costs and how the warranty differs from a slab

Our published range for a typical repair in the area is about $3,300 to $8,500. On older pier-and-beam houses, our historical homes page places re-shimming at the low end of that range and failed-pier replacement plus beam repair at the high end. Encapsulation is priced on square footage, condition and access, the drainage scope and the size of the dehumidifier, so there is no honest flat price before someone has been underneath.

Warranties differ by the kind of work. Pier-and-beam re-shimming carries a one-year transferable warranty and pier-and-beam wood repairs carry a two-year transferable warranty, while pressed pier systems on slabs carry our lifetime transferable warranty. Shims are adjustable by design, and a floor on clay will need attention again someday. If your house has both a slab section and a raised section, my comparison of pier types for slabs covers the slab side.

Starting with a measurement

Our evaluation is free and carries no obligation. I measure the floors, look at the crawl space and the drainage, and explain in plain terms what has moved and why. You get a written, itemized estimate on the spot or within 24 hours, and if the floor is within what an old house can reasonably be expected to do, I tell you that instead.

Most pier-and-beam repairs are finished in a few days, and families stay in the house throughout. If you want to know what the days of work look like, my walk-through of a foundation repair week covers the sequence, from the first measurement to the final readings.

Questions people ask me