How to Repair Brick and Block Foundations
Most often, the cause of damage to brick foundations is cracked mortar. If the damaged area is manageable, a do-it-yourselfer can easily perform the necessary repairs. Bricks were once used extensively to construct foundations. Today, however, if a foundation doesn't consist of concrete, it's probably constructed of concrete block. In either case, brick and block have one thing in common: They're joined together with mortar.
Unfortunately, over time, mortar deteriorates. Cracked and deteriorating mortar joints aren't only unsightly, but they also diminish the integrity of the surface and can allow water to get behind the brick or block, causing major damage. You prevent this problem by tuck-pointing the brick or block foundation, which means removing and replacing cracked or missing mortar.
If the cracked or deteriorating mortar is extensive (an entire foundation, wall, or wainscot), tuck-pointing is a project that's best left to professionals.
To do the repairs yourself, follow these steps:
Chip away cracked and loose mortar by using a slim cold chisel and a hammer. Remove the existing material to a depth of approximately 1/2 inch.
Wear safety goggles to avoid catching a piece of flying mortar in the eye. Use the cold chisel slowly and carefully to avoid damaging the surrounding brick. Use a brush to clean up all the loose material and dust after you finish chiseling.
Prepare your mortar and allow the mix to set for about five minutes.
You can purchase premixed mortar, or you can create your own batch by using one part masonry cement to three parts fine sand. In either case, you want to add enough water to create a paste — about the consistency of oatmeal. It's best to keep the mix a touch on the dry side. If it's too runny, it'll be weak and will run down the wall, making it difficult to apply.
Brush the joints with fresh water.
Doing so removes any remaining dust and prevents the existing mortar from drawing all the moisture out of the new mortar. Otherwise, the mortar can be difficult to apply and is likely to crack.
Apply the mortar by using a pointing trowel.
Force the mortar into the vertical joints first and remove the excess (to align with the existing adjacent mortar) by using a brick jointer. The brick jointer helps create a smooth, uniform finish. After you've filled in all the vertical joints, tackle the horizontal ones.
Avoid applying mortar in extreme weather conditions; mortar doesn't set properly in such circumstances.
A week or two after the mortar has set, apply a coat of high-quality acrylic or silicone masonry sealer.
Seal the entire surface — brick, block, and mortar. The sealer prevents water damage, which is especially important if you live in an area that gets particularly cold. Unsealed brick, block, and mortar absorb water that freezes in cold weather. The water turns to ice and causes the material to expand and crack. Periodic sealing prevents this problem from occurring.