If you’re researching how to brace a foundation wall, chances are good you have a problem to fix. In many cases, foundation walls fail due to lack of support, or some outside factor like soil erosion. When foundation walls fail, the tell tale sign is usually a crack that appears vertically, along with additional sagging of the structure the foundation is supporting. Today we will discuss how to design and inspect a foundation wall and how the professionals approach bracing one.
Why Do Foundation Walls Have to Be Braced?
Foundation walls tend to be underappreciated considering the job they perform. As the name suggests, often these foundation walls support more than the enormous weight of the structure above. Unless a home sits on a very flat lot, chances are very good that the foundation walls will also be supporting backfill.
In most situations, backfill is dirt that has been dug up from either the footings or grade work on the lot. Most building codes require that backfilled dirt slope away from the home’s foundation in an attempt to avoid the aforementioned erosion problems. However, as landscaping and outdoor features are added, root systems and collecting water can exert too much pressure on the foundation, leading to cracks and sagging.
For this reason, foundation walls must be adequately braced for the application, or they will likely fail in the future. Bracing can be accomplished in a number of ways, depending on the structure and what the foundation walls will be supporting. For example, if the structure is built into a sloping lot or hillside, the foundation wall facing the slope will be supporting the weight of the dirt, all of the shrubbery and trees, and all of the water in the dirt. As a result, the foundation walls must be constructed to resist this enormous weight.
How Do I Know How Much Bracing My Foundation Walls Require?
It might be surprising to learn that the dimensions and materials required for constructing a foundation wall is one of the easiest steps in the process. This is because in those municipalities with building codes, a whole section of the book is dedicated to foundation and retaining walls, eliminating guesswork. For example, given the home’s dimensions, the slope of the lot, and a set of prints, a technician can use the building code tables to design and support an effective foundation wall. Design features may include filling the wall with concrete, adding rebar, adding thickness, and using diagonal bracing.
Another residential example might be when a foundation wall is shared between a crawl space and a ground level garage. Although the garage level will generally be ground level, the actual first floor will be higher, unless the home is on a concrete pad. In this common design, the foundation wall between the crawl space and the garage will likely need to support backfill on the crawl space side. Generally speaking, any wall over 48” tall will require additional bracing, such as the addition of fiberglass infused concrete and steel rebar.
Another popular, but relatively expensive, foundation wall bracing solution is a process called jacketing. Jacketing refers to the addition of fiberglass reinforced concrete and/or steel rebar to an existing foundation footings. Sometimes, age and less than perfect construction can cause inadequately poured footings to lean, crack, and buckle. Jacketing can alleviate this problem by essentially re-pouring the footings on top of the original, as long as the underlying issue has been corrected.
Professionals accomplish this by excavating the area around the area, often on both sides. Digging under a home to expose the footing can be a chore, but reinforcing only one side of a foundation wall can be problematic, especially if the problem was caused by soil erosion. Jacketing is often accompanied by a french drain or other drainage method to prevent the problem from recurring.
Another foundation bracing option involves the use of steel and pressure treated lumber. Steel bracing is the typical solution for sagging foundation walls when the bracing will not impact daily life. An example might be an unfinished basement, where a concrete pad adjoins a sagging masonry wall. Using common steel bracing however, can impact the use of the space, as the bracing often has to be substantial.
Steel bracing can be accomplished in any number of ways, including installing steel rods placed inside the wall, steel strapping, and simple steel corner bracing. The design of the structure will usually dictate the method used, but they all are effective and durable. Steel corner bracing is usually the least expensive option, but as mentioned, these braces will extend away from the wall, potentially making the space unusable. Here we will describe the process an experienced do-it-yourselfer or professional might use to brace a sagging foundation wall in an unfinished basement.
Step 1 Building the Brace
In most situations the brace will be a simple triangle made from straight, pressure treated lumber reinforced with steel in the corners. The primary goal at this stage is to prevent further damage. The brace should be as high as the wall and contain as many diagonal components as possible, as this will increase the strength. Steel brackets are added to the right angles on both sides on the brace, as this will prevent the brace from separating under pressure.
Step 2 Drilling the Holes
Once the brace is built, it can be moved into place and marked for drilling. In most situations, heavy gauge concrete screws are used to secure the brace to both the foundation wall and the concrete floor, but concrete anchors can also be used. Because it will be resisting so much force, these screws or anchors should be no more than 12” apart and extend into the foundation and concrete floor by at least 1 ½”. Most professionals use a hammer drill to make these holes, but any drill with a masonry bit can be used.
Step 3 Mount the Brace
Next, the brace is placed firmly against the foundation wall and the screws are installed. The pros will often use a heavy duty cordless impact driver for this step, but a ratchet and socket will also work. Exerting force towards the foundation wall while installing the screws is usually unnecessary. Just snug contact with the wall should be enough to make the brace effective, as the goal is to prevent further movement.