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Working with Mortar

Laying bricks in mortar is a skill that requires practice before you become proficient. You probably will never be able to throw mortar and lay bricks as quickly as a journeyman, but with patience you can learn to make straight walls with clean joints. Professional masons take their mortar seriously. Mortar must be just the right consistency, neither soupy nor dry. It must have the correct ratio of sand, lime, and cement. Otherwise, laying bricks will be a struggle and it will be difficult to keep the courses even. For small jobs and repair work, use premixed mortar that contains sand. For larger jobs, you may be able to save money by buying the sand and the cement separately and mixing them yourself.

Tools: Mason’s hoe, mortar box or wheelbarrow, brick trowel, mortarboard.

Caution! Avoid Cold Weather - Mortar loses its strength if the temperature drops below 40 degrees. Don't risk ruining your work. Hold off on the project and wait for warmer weather.

1. Mix the mortar. Consult your supplier for the best mix for your area and your project. In most cases, a good ratio is 4 parts sand, 1/2 part lime, and 1 part mason’s cement. Adding lime and sand weakens the mortar. Measure by shovelfuls. Mix small batches in a wheelbarrow; for larger jobs use a mortar box. Shovel in half the sand, then all the mortar and lime, then the rest of the sand. Mix the dry materials thoroughly, then carefully mix in clean water a little bit at a time.

2. Add color pigment. If you want to color the mortar, add the pigment to your dry mix. Follow label instructions carefully. Keep accurate track of your proportions so if you mix another batch you can achieve the same color. If you retemper (remoisten) colored mortar, you will change its color, so don’t mix too large a batch and don’t let it dry out.

3. Test the mortar. Pick up a small amount of mortar with your trowel and quickly turn the trowel upside down. If the mortar sticks to the trowel, it is the correct consistency. If the mortar stiffens before you use it all, add water and remix. (Don’t do this with colored mortar.) But if it stiffens a second time, throw it out and make a new batch.

4. Pick up the mortar. Drop a shovelful of mortar onto the mortarboard. Place the mortarboard close to your work and keep it at a comfortable height so it will be easy to move mortar onto the wall. Simply getting the mortar on your brick trowel in the correct position takes some practice. Slice off a gob and shape it so it is about the size and shape of your trowel. Scoop it up with a smooth sweep, giving a slight upward jerk with your wrist to make the mortar stick firmly to the trowel. Take the time to practice this essential technique.

5. Throw the mortar. Bricklayers talk of “throwing” mortar for a reason. Don’t try to carefully place it. In one motion, flick your wrist and pull the trowel toward you. Plopping the mortar onto the bricks helps it adhere better. Using a standard-size brick trowel with the correct amount of mortar, you can throw enough mortar for two bricks.

6. Furrow the mortar. Spread the mortar to an even thickness if necessary. Lightly draw the point of the trowel across the length of the mortar to make a furrow down its middle. Don’t make the furrow too deep or you may form an air pocket.

7. Butter the brick end. Some bricks stick better if they are dampened. Ask your supplier if this is recommended. After the corner brick is laid, butter one end of the other bricks using a scraping motion with the trowel.

8. Place the brick, remove excess. Place each brick so you have to slide it only slightly into place. Push it firmly up against the preceding brick. Immediately slice off the excess mortar oozing from the sides; use this excess as part of your next trowel load.

Building Mortared Stone Walls

Choose stones that blend well together, both in color and texture. A good variety of sizes not only looks better, but it also makes it easier to find the correct size of stones without having to cut them to fit. Ashlar is best to work with, but semidressed stones or rubble work well also. Have the stones delivered as close to your work site as possible to minimize lifting. Be prepared for some difficult physical labor. You’ll have to lift, shift, and try different stones to get the best fit.

Tools: Round-point shovel, tamper, mortar box and hoe, drill or hammer, mason’s line, brick trowel, wedges, brush.

Working with Mortar - Don’t allow excess or smeared mortar to dry and set on the stones. Every stone or two, take the time to wipe the stones clean with a wet rag. It is much harder to remove excess mortar once it sets. Because stones are not as porous as bricks or blocks, they do not absorb much moisture and mortar sets up more slowly. If mortar squeezes out quickly, sprinkle on a bit more mortar mix or Portland cement to absorb water and stiffen the mortar before setting on a stone.

1. Lay a concrete foundation. Unlike a dry-laid stone wall, a mortared wall develops ugly cracks if it settles unevenly. Dig a trench about 6 inches wider than the wall and 6 inches deeper than the frost line or at least 12 inches deep. Tamp at least 2 inches of gravel at the bottom, position two pieces of reinforcing bar, and pour at least 8 inches of concrete. Finish the concrete footing so it’s 2 inches below grade. Make two batter guides out of 1x4 lumber; use these to make sure your wall batters, or slopes inward, about 1 inch per rising foot on both sides.

2. Lay the first course. Allow the concrete foundation to set and cure for several days. Spread a 2-inch-thick bed of mortar. Start on the end with a tie stone—a stone that spans the width of the wall. Use large stones along the visible face of the wall and fill in the middle with smaller stones and mortar. Tap the stones with the handle of your trowel to force air pockets out of the mortar.

3. Lay the stones. Position the batter guides at each end of the wall and use mason’s lines to make sure you maintain a uniform slope and line up the stones straight. Dry-fit several stones, remove them, throw the mortar, then set the stones in position. Place tie stones about every 4 feet in alternating positions for each succeeding course. If a heavy stone squeezes out too much mortar, use wood wedges to support the stones until the mortar sets. Maintain uniform joint spacing.

4. Rake the joints. As you complete a section of wall, use a piece of shim or a scrap of wood to scrape away mortar to a depth of about 1 inch. Follow with a stiff brush and a wet rag if necessary to make sure stones are clean and the joints are uniform.

5. Build second lead, fill in the middle, and top with capstones. Use flat, smooth stones for the visible ends of the wall. Build up the ends, called leads, first. Lay no more than three courses of stones in a day because the weight of the stones will squeeze mortar out of the bottom courses. Fill in the middle section, again dry-fitting the stones, removing them, laying on plenty of mortar, and carefully setting the stones in the mortar. Remember to include tie stones every 4 feet or so. Cap off the wall with a row of large, flat stones. When you mortar these stones on top of the wall, do not rake the joints. Leave them flush with the surface of the capstones to keep water from sitting in the joints, freezing, and damaging the wall.

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