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Buildings sometimes settle and cracks develop in the mortar joints. Older mortar will succumb to the elements and simply erode away. This is often the case if water leaks from a gutter or downspout and is allowed to stream over the face of a brick or stone wall.
I have chiseled out many a mortar joint. It is tedious work, plain and simple. If you want excellent results, be prepared to take your time. The brick must not be chipped in the process. You can easily chip brick or stone if you aggressively attack the mortar joint. Hard blows from a hammer will transfer concentrated blasts of energy to the mortar. This energy is often absorbed by the brick. Chips and cracks are common if you hammer too hard. The chiseling action must be directed sideways in the joint, not towards a brick.
Mortar Removal Tips and Techniques
The removal of the old, loose mortar is the most important part of a tuckpointing job. If you cut corners here, you might as well forget about doing the job at all.
There are three ways to tackle the job: hand work with a hammer and chisel; the use of power equipment, or a combination of the two. If you have just a little repointing to do, a hammer and chisel may be the trick. However, if there is a significant amount of work you may combine a grinder or a hammer drill to assist you.
IMPORTANT TIP: Power equipment will permanently damage brick surfaces. You will become fatigued and a drill, power chisel, or a grinder will slip and scar or chip a brick. I only advocate the use of power equipment for small periods of time when you are fresh and alert.
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The task of removing mortar by hand is made easier if you choose the correct chisel. Purchase a special brick pointing chisel. It is a small, flat chisel that resembles a miniature, thickened carving knife. The chisel comes to a point and the shaft of the chisel is approximately 1/8 to 3/16 inch thick. This way it can easily fit between two brick.
You need to chisel approximately 3/4 inch deep into the old mortar to enable you to get a good bond with the new mortar. The new mortar needs to be able to have adequate brick surface to adhere to.
If the mortar is old lime mortar, chiseling will be easy. If the mortar is a rich Portland cement mortar you may have to use a roto-hammer with a 1/4 inch bit. Drill straight into the mortar keeping the holes about 1/4 inch apart. This method will allow you to finish the job with the pointing chisel.
Always remove the loose mortar and dust before proceeding. I always squirt out the joints as well with water. The surface of the old joint must be dust and grit free for a good bond.
Matching Mortar Color
Once you have removed all the loose mortar, you still must invest a lot of time for a perfect match. Mortar texture and color must be matched. Color tinting may be involved. It was not uncommon for masons of old to add natural pigments to the fresh mortar mix. Dirt and weathering forces can cause the mortar to have a different appearance than when first installed. This is especially true of horizontal mortar joints, as you will find in brick walkways. My front sidewalk mortar is very dirty, even though it is only eight years old. When I go to repair a joint, I will be forced to scrub the joints clean with my Stain Solver Oxygen Bleach to make sure the repairs will match.
Look closely at your existing mortar joints. If your house is older you will undoubtedly see lots of sand particles. Notice the different sizes and colors of the individual grains of sand. These small dots of color are responsible for a vast majority of the overall color you see. It is no different than the color photographs you see in the newspaper each day. Those photographs are made up of tiny color dots.
If you want your tuckpointing to match the existing mortar, you must start first with the correct sand. It might not be as hard as you think to locate the sand. The key will be to think about when the house was built and where sand pits were located at that time, not the present locations. Freight, or hauling, is the largest cost when buying sand. That is true today and it was true 100 years ago. For this reason, brick masons try to purchase sand from a convenient source.
Ask the experienced employees at the local brick supply houses and gravel pits where the sandpits of old used to be located. Try to see if there is still sand available from these old pits.
To get a sample of sand from your existing mortar to compare with new sand, you need a little bit of muriatic acid. The acid will dissolve the old lime and cement from the mortar. The net result will be sand in the bottom of the glass or other vessel you choose to use for this simple process.
If you live in a coastal area, where sand often contains sea shells and other calcium carbonate pieces, the acid treatment will not work. The acid will dissolve the sand!
Mix 1 part of acid to 5 parts water in a clear glass if possible. Drop in some of the old crumbling mortar. If the mortar begins to bubble vigorously, that is usually an indication that the mortar contains a high percentage of lime. If there is minimal bubbling, Portland cement may be a majority binder.
In either case, allow the mortar to sit in the acid solution for up to several hours or days. You can redo the experiment after the bubbling stops to make sure the acid has done all its work. When completed, there should just be sand particles in the bottom of the glass. Pour off the acid and get the sand into a paper towel to dry. Once dry, put the sand into a small clear glass or plastic bottle that you can get from your local pharmacist. It's time to go find the new sand. Be sure you look at dry sand samples at the gravel pits and building supply stores. Pay attention to particle size and color.
Installing New Mortar
Once you have found the correct sand, and followed my instructions on how to blend the right amount of lime and cement with the sand, you are ready to point the brick joints. You need two or three simple tools to make this an easy task. Purchase or borrow a regular brick trowel, a small pointing trowel and a tooling jointer. The pointing trowel is simply a thin, rectangular piece of metal that is attached to a wooden handle. They come in different sizes to match the width of the mortar joint. Always use one slightly smaller than the width of the joint. The tooling jointer is simply a tool that creates a profile to match that of your existing joint. Some are concave, others create a V-groove and still others create a line.
You need to dampen the old mortar joint before installing the new mortar. Place mortar on the full sized brick trowel and hold this level with the joint to be filled. Use the small jointing trowel to bulldoze mortar into the joint. Take your time and do not get any mortar on the face of the brick. Strike off any excess mortar and allow the mortar to stiffen before tooling it.
To really match color and texture, you may have to distress the new joint in a month. Acid washing will often create a weathered appearance. Coffee, tea or other colored liquids can add colors to recreate dirt or other stains. Stand back at the street to judge the results of your work.
|Message from Tim:
Years ago while researching a column about cleaning decks, I discovered the wonders of Oxygen Bleach. It is perhaps the 'greenest' cleaner I know of as it uses oxygen ions to break apart stains, dirt and odor molecules. There are no harsh chemicals, and it works on just about anything that is water washable.
I decided to create my own special blend using ingredients made in the USA. In fact, the raw materials in the active ingredient are food-grade quality registered with the FDA. I call my product Stain Solver. I urge you to use it to help clean your mortar. You will be amazed at the results!