How to Reinforce a Brick Foundation
Brick was a common foundation option at the turn of the 20th century. It is no longer. One of the primary reasons for this is that brick wears faster than concrete. Most old brick foundations are now probably in need of repair and reinforcement. While there are many methods to accomplish this, the building of a simple “sister wall” creates an interior wall that reinforces the exterior brick. Concrete is then poured from the outside in between the bricks and the new concrete wall.
Frame the interior sister wall by laying cinder block about 1/2 inch to 1 inch from the brick wall. Since this interior wall is not be exposed to the elements, it need not be perfect. Any gaps can easily be filled with mortar, grout or epoxy.
Lay a layer of mortar about a full inch on the concrete basement floor behind the exterior foundation wall. This is where your hollow-celled concrete blocks are to be laid. These are effective because they can later be filled with concrete. Place the blocks with the cells facing up.
- Frame the interior sister wall by laying cinder block about 1/2 inch to 1 inch from the brick wall.
- These are effective because they can later be filled with concrete.
Pour concrete into the cells of the blocks. If you want even stronger reinforcement, you can place rebar into the cells after pouring a small amount of concrete into them. This is not strictly necessary, but it might give you more peace of mind.
Use a 2-by-4 piece of lumber on the top of the wall if you find a gap. Since you are going to be pumping concrete into the space between the new wall and the failing brick, this wood beam can be removed once the concrete has been cured. What you are doing here is setting up a cinder block scaffolding for poured concrete.
Remove bricks and wood with a chisel from the outside of the foundation in order to make room for the concrete pump.
- Pour concrete into the cells of the blocks.
- Since you are going to be pumping concrete into the space between the new wall and the failing brick, this wood beam can be removed once the concrete has been cured.
Insert the nozzle of the concrete pump into the gap in the exterior brick wall. Pour concrete from the outside into the cells and between the concrete block wall and the brick foundation. This does several things. It increases your insulation to a great extent. It attaches this new sister wall to the failing brick wall, providing the reinforcement. Even if your bricks are falling away from the house, you now have a new means of attaching bricks.
Repair all cracks and holes in the bricks from the outside. After the concrete has dried, you begin from the outside and replace cracked or broken bricks. You can use grout, often 3 parts sand to 1 part portland cement, to all fractures and holes.
- Insert the nozzle of the concrete pump into the gap in the exterior brick wall.
- After the concrete has dried, you begin from the outside and replace cracked or broken bricks.
Spray the newly repaired wall with a rubber membrane liquid spray. This is a waterproofing compound that, when it dries, seals the newly reinforced brick foundation. It is now waterproof, and protected from termites and from radon. You now have a thick, reinforced and watertight foundation that should last.
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- Unless you have a background in this work, have a professional come in and pour the concrete.
- Always order more blocks and mortar than your own calculations say you need.
- Remove all excess cement or concrete from the joints
- It is probably best to have a professional come in and inspect your plans. Most of the work you can do yourself, but before you begin, consult someone with experience.
- New bricks
- Mortar, grout or epoxy materials
- Cinder blocks
- Poured concrete
- Rebar poles (optional)
- Rubber membrane liquid spray