Ask the Builder: A Brick and Mortar How-To Course

Q: DEAR TIM: 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? -- Steve T., Morris Chapel, Tenn.

A: DEAR STEVE: For all intents and purposes, bricklaying mortar is just a glue, used to stick two or more things together into one object.

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. Note that the sand can have a significant impact on both the strength and final color of the weathered mortar joints. Not all sand looks the same, because the small rock particles that make it up are of different colors.

Many old masonry buildings were made with a mortar that had abundant quantities of hydrated lime or just lime and sand. Typically, the more lime, the weaker the mortar. You may think you want a strong mortar, but the lime in the mortar offers a unique self-healing property. The hydrated lime can actually grow crystals that may seal tiny cracks.

One of the most important tasks is matching the mortar to the job. You don't use the same mortar for your brick walls as you do for the mortar joints in your brick patio. The patio mortar needs to be far stronger than the wall mortar, as the patio is subjected to more wear and tear. And if you get freezing weather, the mortar must be able to withstand countless freeze-thaw cycles.

To make a strong mortar for your brick patio, just use pure Portland cement, sand and water. I would make the mixture very rich -- meaning with lots of cement. Try a mixture of two parts sand to one part cement.

Be sure you have all the loose mortar out of the joint and that it's dust free. Spritz the joint to be repaired with a little water and add the mortar. Make the mortar stand a little higher than the brick. Wait until the mortar gets a little stiff and 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 your brick walls, look very carefully at the existing mortar joints. Pay attention to the small, colored grains of sand that are visible. When mortar is first installed and it dries, it's a uniform gray color. This happens because all of the sand is coated with the mortar-cement paste. But over time, Mother Nature erodes the mortar-cement paste from the sand, exposing the different pieces of small rock in the sand. You may see brown, red, gray, white and even green pieces.

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. This will be well worth the effort if you intend to restore your brick walls so the repairs match the original work.

You can purchase bags of premixed brick mortar from a business that sells building supplies. Avoid the home centers, as they usually will not have a selection. You want to match the color of the mortar as well as the strength. The older your home, the weaker the mortar you should use.

Tim Carter can be contacted via his Web site, www.askthebuilder.com/printer_Submit_Question.shtml.