Stabilizing Basement Walls with Steel I-Beams, continued

When my holes are ready, I set an I-beam in each. I place each I-beam tight against the wall, hold it plumb, and brace it in place with a 2x10 block or a piece of 3x3 1/4-inch angle iron, lag bolted into the joists above (Figure 4). The I-beam contacts the wall wherever the wall is farthest out (usually in the middle for block walls and at the top for poured walls).

Figure 4.A worker braces the top of an I-beam tight against the top of the leaning wall (top). The 2x10 brace is fastened to the existing floor joists using 3/8-inch lag bolts sunk into predrilled holes (bottom). Three-inch by three-inch angle iron can be used instead of the 2x10 block. This step is easier with two people -- one to hold the I-beam and block in place, and one to set the lag bolts. The top brace connection varies depending on whether the joists run perpendicular to the wall or parallel. Perpendicular joists supply strong bracing -- a single 2x10 or piece of angle iron spanning one joist bay is plenty. But a joist parallel to the wall is oriented sideways to the force of the wall pressure and can't handle the load by itself. In that case, I place solid blocking into the joist bays for three or four joists back from the wall, then lag a 2x10 into the joists under the blocking (Figure 5). This transfers the load of the I-beam into the whole floor system instead of dumping it all onto the side of one joist.

Figure 5.For bracing perpendicular to the floor joists, the author places solid blocking into at least three joist bays and lag bolts the brace to each of the joists directly under the blocking. The joist nearest the beam could not do the job on its own without this arrangement.

When my beams are pinned at the top, I plumb them up and brace them into the holes at the bottom. It's tricky to hold them still while you grout the bottom and the space between the I-beam and the wall. After years of struggling with that, I started bracing the foot of each beam into the hole with scraps of wood (Figure 6). It's quick and easy, and the wood gets buried in the concrete base of the pier.

Figure 6.The author braces the base of each I-beam in place with small blocks of wood. The wood blocks will be encased in the concrete pier base when the hole is grouted.

Next I grout the space between the I-beam and the wall with stiff concrete (Figure 7). I mix a batch of sack concrete in a wheelbarrow (dry enough to make a firm ball in my hands), put on some rubber gloves, and just pack it into the gap and whittle it smooth. That provides solid support for the wall from floor to sill.

Figure 7.A worker grouts the entire space between the I-beam and the wall with stiff concrete to provide full support for the wall. Excess grout is smoothed away for a clean finish (see photo at beginning of article).

Finally, I fill in the hole at the base of the I-beam, locking it into the earth and the existing slab (Figure 8). That makes the whole assembly one continuous, solid structure. In the six years I've been doing it, I've never seen one of these I-beams budge a millimeter.

Figure 8.The hole is filled with stiff concrete to embed the I-beam firmly into the slab and subbase. The surface is troweled level with the existing slab.

All I've described here is the wall stabilization. Many of these basements also need exterior waterproofing or an interior drain and sump system. As long as the water problems have been dealt with, the basement space can be finished any way the homeowner wants to once the I-beams are set (Figure 9). There's no need to leave access to the I-beams -- they can be simply painted, or boxed in and buried.

Figure 9.The completed I-beam installation (top) supplies reinforcing for the wall from footing to sill at 3 to 6 feet on-center. In the example below, the author then applied fiber-reinforced plastic panels to the basement walls. The basement is now ready for further finishing.

Costs and Scheduling

Jobs that require excavating call for careful estimating. There are dozens of factors to keep in mind -- access, proximity to neighboring homes, attached steps or other structures, landscaping, and possible low overhangs that can impede the excavator, to name a few.

But estimating a basic wall stabilization job is simple. Given a typical 30-foot wall to brace, I know I can break out the floor, dig the holes, and place the seven or eight beams that are needed in one day. I know it will take half of a second day to do all the grouting and clean up.

The only materials costs are for the beams, grout, lag bolts, and wood or angle iron for top bracing -- which comes to about $50 total in materials for each 8-foot I-beam I install. I price jobs to the homeowner for about $200 to $250 per beam, which covers labor, overhead, and profit.

For small jobs, I don't take a deposit. I just put the house on my schedule and call the owners a day or two before I start. Once I do start, I stay on the job until it's done; when I finish, they can pay me with a check or credit card. With this arrangement, I don't feel under pressure if I'm a day or two late getting started.

These small jobs often lead to larger jobs. Many of the people whose basements I've fixed will call me back later to finish out the space, or to do some kind of exterior grading or concrete work. And they often refer me to their friends as well -- I get most of these jobs through word of mouth.

That's especially true of the homeowners who like to watch. Some homeowners don't want to know what we're doing, as long as we get it done. Others will pull out lawn chairs, pack a lunch, and sit and watch us for the whole time. Every few minutes, I find myself stopping to explain what we're doing and why. But that doesn't bother me a bit -- the way I figure it, that makes them a little more educated. And it also means that when I'm done, they're that much more likely to refer me to someone else who needs my help.