Knowing the early warning signs of foundation troubles can head off problems that ultimately could cost tens of thousands of dollars to fix. The sooner you identify potential problems, the easier — and less expensive — it is to fix them.
The 4 Basic Indoor Warning Signs
Houses settle over time, and a little unevenness isn’t cause for panic. At the same time, you’ll want to be alert to these warning signs that more dramatic changes are taking place:
A door begins to jam or fails to latch.
Cracks appear in walls, especially over doorways, windows, or where walls meet ceilings.
Cracks open in vinyl or ceramic tile over a concrete floor.
Windows that used to open and close easily suddenly begin to stick or won’t close completely.
Check the Outside
Moving outside, check to see if your foundation is straight by sighting down the length of your foundation wall from each corner. The walls should be basically straight, both up and down and from side to side. Check for leaning walls with a level.
A bulge or curve in either a block foundation or a poured concrete wall could signal that the foundation has shifted, or that the soil around your foundation may be expanding and contracting, putting pressure on walls.
Probe Concrete for Weakness
If your house has a poured perimeter foundation and the concrete appears to be chipping and flaking, poke it in a few places with a sturdy screwdriver. The concrete should be so hard that you can’t damage it.
If you manage to chip it or break a piece off, the concrete could be deteriorating because the mix contained dirty or salty sand, or too much water. This problem, common in homes built in the early 1900s in some parts of the country, has no remedy short of a new foundation.
Checking Structural Components
Foundation systems have other members besides the perimeter foundation wall. In your basement or crawl space, look for posts and concrete supports, or piers. Posts should stand straight and be firmly planted underneath the beams they support. Bottoms of posts should rest firmly on concrete piers.
You shouldn’t find puddles or see framing that’s wet. Check for rot by probing wood posts with a screwdriver or awl.
Puddles and other signs of moisture in a crawl space may indicate poor drainage around the perimeter foundation. Be sure that gutters aren’t plugged, and that soil slopes away from the foundation at the rate of 6 inches for every 10 horizontal feet.
Reading Foundation Cracks
As concrete cures, it shrinks slightly. Where the concrete can’t shrink evenly, it tends to crack. Concrete and block foundations usually have at least a few cracks. The trick is recognizing which are insignificant and which are serious. Here’s a list from least to most serious:
Hairline cracks in the mortar between concrete blocks are rarely worth worrying about.
Cracks at an L-shape section, such as where a foundation steps down to follow a hillside, are probably shrinkage cracks, especially if they meander and taper down to a hairline. These aren’t a structural issue, though you might need to plug them to keep the basement or crawl space dry.
Stair-step cracks in masonry joints are a bigger concern, especially if the wall is bulging or the crack is wider than ¼ inch. A plugged gutter or other moisture problem outside is probably exerting pressure on that part of the wall.
Horizontal cracks are most serious. It may be that water-saturated soil froze and expanded, pushing in and breaking the foundation. Or, you may have soil that expands when damp and shrinks when dry. The bad news: You probably need a whole new foundation.
Getting a Professional Opinion
A structural engineer can determine whether any of these warning signs point to normal settling or to structural damage. Expect to pay $500-$700 for a structural engineer to inspect your foundation and provide an evaluation, and as much as $2,000 for a full set of drawings for an engineered solution.
What Does Fixing a Foundation Cost?
These are several methods for fixing foundation wall problems, including:
Bolting on steel braces ($500-$70 each, spaced about 6 feet apart along the wall) or using epoxy to glue on straps of carbon-fiber mesh ($350-$450 each, similarly spaced).
Underpinning the foundation with helical screws or concrete piers. Installation costs $1,200-$1,500 per pier, with one every 6 to 8 feet.
A whole new foundation, which can run up to $40,000.
If you find small cracks (less than 1/16-inch wide), paint over them with a concrete waterproofing paint (about $25/gallon). Then check periodically to see whether the paint has cracked, which means the gap is opening up under pressure.
Jeanne Huber is the author of 10 books about home improvement. She writes a weekly column about home care for the Washington Post.