The right mix is important when replacing mortar

Q: Brick mortar and I don't get along. At my house, the brick and mortar are falling apart. It's happening on the walls and in a brick patio in my rear yard. I desperately need a mortar how-to course so I don't end up with a huge mess. What are some of the important steps in brick mortar repair? Are there special tools that make the job go faster and look more professional?

A: Bricklaying mortar is a fantastic product when you stop and think about it. For all intents and purposes, it's just a glue. You use it to stick two or more things together. You may not know it, but there's an enormous amount of science involved in making mortar for brick. I can't begin to scratch the surface in this column.

There are many different types of brick mortar, many with different strength properties. A standard mortar is a mixture of Portland cement, hydrated lime and some form of clean, washed sand. The sand can have a significant effect on the strength and final color of the weathered mortar joints.

In my opinion, one of the most important tasks is to match the mortar to the job. You don't use the same mortar for your brick walls as you would to patch your brick patio. Patio mortar needs to be far stronger than the wall mortar.

To make a strong mortar for the patio, use pure Portland cement, sand and water. I would make the mixture very rich, meaning that there is lots of cement in the mix. Try a mixture of two parts sand to one part cement.

Get all loose mortar and dust out of the joint. Spritz the joint with water and add the mortar. Make the mortar stand up a little higher than the brick. Wait until it gets a little stiff, then scrape off the excess with a small pointed trowel. If the mortar smears onto the brick, you're not waiting long enough.

To repair the mortar in walls, look at the small, colored grains of sand in the mortar. Initially, when mortar dries it's a uniform gray color because the sand is coated with the mortar-cement paste. Over time, the mortar-cement paste erodes, exposing the pieces of small rock that make up the sand.

Visit a local sand pit and look at the different sands. Note that there can be a difference in both grain size and color. You want to match both as closely as possible. You also want to match the strength of the mortar. The older your home, the weaker the mortar.

Tim Carter is a licensed contractor. To view previous columns or tap into his archive of information and sources of building materials, go to www.askthebuilder.com. You can write to Tim Carter at P.O. Box 36352, Cincinnati, OH 45236-0352.