Sheared brickwork

Foundation Repair Guide


Foundation repair

Foundation repairs range from simple DIY fixes to major reconstruction. Here’s what you need to know about your options, and when to call in a Pro.

Fixing foundation problems should be a priority for every homeowner. Foundation repairs prevent little problems from becoming bigger, keep your home safe, and protect the value of your property. Fortunately, foundation problems tend to develop and worsen slowly, giving you time to make a thorough evaluation and decide on the proper course for repairs.

Thin cracks
Cracks less than 10mm wide require the easiest foundation repairs, especially if they’re located where concrete tends to crack naturally from shrinking as it cures. You can probably leave these cracks as-is. But if water is seeping through or you’d like to seal cracks for cosmetic reasons, apply a good-quality epoxy putty.

Wide cracks
Horizontal cracks, vertical cracks wider than 10mm or stairstep cracks in bricks tip you to more serious problems. You can hire a contractor to plug deep cracks by injecting epoxy ( ~ $2,000), or do it yourself with epoxy putty, but either way, you’ll only be stopping water ingress.

Patching cracks won’t make your house level again or stop whatever forces caused the cracks in the first place.  [ eg corroding lintels or subsiding foundations.

Basic foundation issues.
A common culprit is water accumulation in the soil around the foundation, which expands the soil and puts pressure on walls and foundation footings, causing cracks to appear. Check to make sure all gutters and downspout drains are in good working order, and that the soil around your foundation is properly graded—it should slope at least 20mm for every 1 meter. Quite often foundations are required to have a perimeter drain system that channels sub-surface water away from the foundation. The drain system is made of  perforated plastic pipe buried in a gravel bed. It usually drains externally (a pipe that opens onto a low spot in your yard), or connects to the street curb.

It’s possible for this drain to become blocked, causing water to accumulate in the soil and putting pressure on your foundation walls. If you suspect a blocked perimeter foundation drain, seek the advice of a licensed foundation repair specialist.

Trees growing in the vicinity of your footings is an all too common a cause of foundation failures causing foundation heave and then differential ground moisture from the root suction causing the surrounding soil to contract.

Buckled walls and severe cracks
A perimeter foundation that has tipped, bowed, or severely cracked requires substantial reinforcement to prevent further deterioration. Repair the walls from the inside with  steel braces, carbon-fiber mesh, or wall anchors spaced 1500mm or so apart along the entire wall.

For about $1000 each, steel braces install against the wall and attach to the floor and overhead joists, blocking further movement. However, they intrude into the basement area about  150mm, making it difficult to finish the walls. A newer experimental option being practised overseas , is almost invisible, involves spreading epoxy in vertical strips and then pressing on carbon-fiber mesh to lock the wall in place.

Wall anchors are similar to large bolts. They consist of metal plates in your yard (installed by excavating), and metal plates on the inside of your foundation walls The plates are connected by steel rods buried horizontally. The connectors are gradually tightened to stabilize and help straighten the wall. Wall anchors are placed every 1500mm, and cost average $850 each.

If a foundation wall bows severely (more than 75mm) or if you want to make it straight again, you probably won’t be able to fix the problem from the inside. You may need to excavate part or all of the foundation and rebuild it— in the order of  $10’s of thousands.

Sunken areas
If a broken water pipe, a plugged gutter, or a drainage problem in your yard has sent enough water cascading alongside a perimeter foundation to undermine an area, a contractor might be able to shore up the area with more concrete or shim the sill plate to make the area level again. Or you might need to tear out a section of the foundation, repour, and tie the new section into the old with rebar and epoxy.

Simple fixes with concrete and timber might cost as little as $500 or as much as several thousand dollars. Just be sure that the underlying cause is fixed first, or the repair won’t last.

Foundations on reactive soils
If your house is out of kilter and there is no obvious reason, it may sit on soil that expands when damp and shrinks when dry. This so-called “expansive soil” is found in all states of australia and has damaged about a quarter of all houses in the U.S.[no figures for Australia].,and are in need of foundation repair according to the American Society of Civil Engineers. If you suspect you have the problem, check with your local building authority to see if reactive soils exist in your area.

Dealing with this kind of soil is most difficult if you have a slab foundation because access is to underneath the slab is limited. First, try to reduce moisture fluctuations under your house. Make sure soil slopes away from the house, and pipe away all gutter water. Replace water-thirsty landscaping within 1.5 meters of the walls with plants that need little water or, even better, install a concrete path around the house so rainwater can’t soak in there.

Root barriers are effective as a moisture control mechanism

If you live in a damp climate and notice settling issues such as sticky doors during droughts, try the opposite approach. Keep the soil evenly moist by running drip irrigation around the perimeter during dry spells. If you see cracks in the soil, it’s too dry. But don’t dump water into a crack; irrigate 500mm away from the foundation, and use an automatic timer so you add a little water several times a day rather than a lot all at once.  This approach is not entirely reliable but is cheap.

A contractor may be able to raise a sunken area in the middle of a room by “mud-jacking,” … pumping a cement slurry under the slab under pressure. Mud-jacking can’t raise load-bearing walls, however. For that, you need to support the slab with underpinning that reaches down to a more stable layer, a fix that costs $5,000 to tens of thousands of dollars.

Options for underpinning include steel posts driven in hydraulically, helical piers, which have blades that screw into the soil. Installation costs $1,200-$1,500 per pier, with one every 1500mm. Another option consists of drilling holes 300 – 450mm diameter down to good load bearing soil or rock and fill with reo and concrete.

 Structural engineer Involvement with foundation repairs
Trustworthy advice comes from a structural engineer. An initial visit (about $500) should reveal the severity of your problem and tell you what to do next. If you need a full engineering report, expect to pay several thousand dollars. You might also need a soils engineer [geotech] and core samples, doubling the cost.

In the end, you should get a written report that makes specific recommendations and lays out pros and cons of each option. If you need a complicated fix, you might want to hire the engineer by the hour ($100-$200) to inspect while work is underway.

If you don’t need the piece of mind of an engineer you can call direct a foundation repair contractor for an appraisal and quotation for $250 generally a cost refundable if the work proceeds