How to Repoint a Cinder Block Wall

Cinder block walls, chimneys and siding can break down over time. If you catch the crumbling mortar in time, you can save the structure from tumbling down with a fairly easy process. Pointing is the external part of mortar joints in masonry construction. When weather and time chip away at the mortar between the cinder block bricks, it's time for a repoint. Water can leak into the crumbling mortar and cause serious damage. When it's freezing, the water turns to ice and expands to push against the cinder block that's already weak in its position on your once sturdy wall. Fixing a cinder block wall takes a few steps but isn't terribly difficult to tackle with basic tools and information.

Before you begin, take a gander at your mortar. Figure out where the damage began, and you'll save yourself future repointing. If the cinder blocks themselves are cracked, you may have a foundation problem that needs to be addressed first. Cracks are common, so if you have a crack that's less than 2 millimeters in width, you may be better off walking away.

Once you've fully inspected the wall and decided where the deterioration originated from, you'll want to remove the crumbling mortar down to the point where it's rock-hard. For Portland cement, which is generally used for cinder block walls, you'll need a grinder, caulking cutter with a diamond blade or other handheld machine to smooth down to the middle of the joint. A chisel and hammer can be used for tight spaces and small jobs.

Pour 3 parts sand and 1 part masonry cement for a basic mortar mix into an appropriately sized bucket. Add two gallons of water and mix from the bottom up. Add another gallon and continue mixing, adding water as you go until you have a smooth consistency. There are many premixed mortars available as well. Refer to the directions on the masonry cement you choose for best results.

Apply the mortar to the deepest affected area first and build out from there. It's not as simple as slapping on some mortar and smoothing it over. You'll want to apply layers ¼ of an inch at a time to create a strong bond that hardens. Once the new mortar is flush with the old cinder block, spray it down with water. You'll want to do this often. Remember it as two and two, every two hours for two days, then four and two, every four hours for two days. Cover it with plastic tarps or burlap and anchor it so that sunlight and rain can't reach your work and wreak havoc. After about a week, you can apply an acrylic or silicone masonry sealer to slow down deterioration.

If a block needs replacing, you'll need a drill and chisel. Place ¼-inch holes in the center of the brick with your drill to make it easier to chip it out with the chisel. A small sledgehammer can help if the cinder block is stubborn. Brush away debris and blow out the dust with condensed air before spraying it down and wiping away any dust. Mix and apply your mortar around your new brick before putting it gently in place with a pointing trowel. Try to keep it steady as you level it with its neighbors by applying mortar on the sides to make the joints even.

By taking the time to repoint, you can have a secure cinder block wall for decades and save yourself a heap of trouble over the long term.