patching masonry cracks


Old 09-12-00, 09:49 AM
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I have some cracks in the mortar btween the bricks on the outside of my house. What is the best product and method to repair them?
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Old 09-12-00, 10:52 PM
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Deteriorated mortar between the bricks calls out louder for repair then cracks, especially if the mortar is hard and the crack does not appear to be getting any larger. The house may have shifted because of frost heave or a particularily dry summer, and this movement may have caused the crack.

You really can't repair a cracked mortar joint without relaying the brick. You can cut out the mortar to a certain depth and remortar, but this is just a cosmetic repair, and the brickwork is still cracked behind that repair.

If the crack doesn't appear to be getting any larger, I'd just caulk that crack just to prevent any rain water getting into the wall through it.

If you want to do the cosmetic repair, use a hand grinder fitted with a masonary blade to grind out the mortar between the bricks. However, if the mortar is hard, you'll find this is awfully slow going, even with a power tool doing the work. A chisel is even slower going.

Also, replacing mortar can often yield a repair that looks worse than the crack because it's often hard to match the colour of the old mortar. This makes the repair much more visible because the different colour mortar stands out much more than the crack did.

After having removed the old mortar to a depth of about 3/4 inch, wash out any dust with a wet paint brush, allow the brick to dry so that the surface appears dry, and then pack the joint with new mortar. I find the easiest way to do this is to put the mortar on top of a plastering trowel and pack it into the joints with a jointing trowel. Jointing trowels come in different widths and can often be purchased right at the brick yard, but I would expect Home Depot to sell them too.

Once the mortar has set up to the point where it's no longer soft enough to leave an impression in it with your thumb, pack the mortar in the joint with a tool called a "spoon". The idea is that by packing the mortar into the joint, you make the surface harder and denser and less prone to weathering. You can also just use a piece of 1/2 inch copper pipe as a spoon. If you take the copper pipe to an electrician and have him put a shallow "S" bend in it to provide clearance for your fingers and so it will actually ride flat against the wall, it works better.

Clean off any mortar from the face of the bricks. I've never used acid to do this. I just clean it off with a damp Scotchbrite scouring pad and hold up a wide taping knife to protect the fresh mortar joints while I'm cleaning the brick face.

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