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Block-Laying Basics - Continued

Because the moisture content of sand varies, so does the amount of water that must be added to the mixture to get it right. Basically, the mortar should be as wet as possible and still be workable. Wet mortar is sucked up into the pores of the units and, in the finished wall, forms a tenacious bond. However, mortar that is too wet is just about impossible to work with and makes a mess of the finished wall. And mortar that is too dry does not bond well with the units.

Trowel Techniques

Good, workable mortar is soft and mushy but not soupy. If you're mixing it with a mechanical mixer, it should flow through and around the paddles in thick globs, leaving noticeable voids in each paddle's wake; if you're mixing it with a mortar hoe, it should pass easily through the holes in the blade, forming cylindrical-shaped columns of mortar as it does. Workable mortar can be loaded up on a trowel without flowing off the sides yet yields readily when a brick is pushed into it.

There are two main troweling skills: spreading bed-joint mortar efficiently and buttering (in other words, getting the mortar to stick to vertical and inclined surfaces). With bed joints, the object is to bring as much mud to the wall as possible without dropping it en route. So you first scoop up a full but manageable trowelful of mortar and bring the loaded trowel a few inches above and in line with the units you're covering. Then you drop your arm, rotate your wrist, and pull the trowel toward your elbow. With practice, these steps become one fluid motion that leaves a nice line of mortar on the tops of brick or the face shells of blocks.

Troweling Tips

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To efficiently spread bed-joint mortar, the author brings his loaded trowel to the footing, gives the trowel a little downward motion, then stops abruptly.

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Next he quickly rotates his wrist while pulling the trowel back, leaving a uniform line of mortar.

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When buttering bricks or blocks, he picks up about half a trowelful of mortar, then gives it a good hard shake by thrusting it down and pulling it back up sharply.

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This flattens the mortar against the trowel (D) so that it will stay put when the trowel is turned over.

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When buttering, the trick is to keep the mortar from sliding off the trowel. Begin by picking up about half a trowelful of mortar. Hold the trowel so the mortar is facing up, then give the trowel a good hard shake by thrusting it down and pulling it back up sharply. This motion — which flattens the mortar against the trowel so that it stays put when you turn the trowel over — comes in handy when you need to do things like butter the ends of bricks and blocks, apply mortar to the top edges of hollow blocks, or butter the edges of bricks laid in a rowlock pattern.

Work From the Corners

Whenever possible, I design a foundation so that each course can be built with full blocks. Before laying any block, I lay the corner blocks, then snap lines from corner to corner. To maintain accurate spacing while laying the block, I mark 16-inch centers along the chalk lines. This helps keep the mortar joints consistently sized and ensures that the last block in each course will fit into place.

Laying the First Block Course

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Block courses start at the corners; a string stretched between the two corner blocks helps align the remaining blocks in the course, while pencil marks placed 16 inches on-center on the footing help the author space the blocks properly.

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When setting the last block in the course, he orients it so that the flanged end is dry, which creates a bigger opening that's easier to fill with mortar.

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After setting the block, he throws mud in the joint until it's full.

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Then he  uses a 3/4-inch tuck-pointer to pack the joint.

I work from inside the wall, with all of my tools and materials set up within the footing perimeter so that I don't have to reach over the string lines. I set my first pair of corner blocks in mortar, aligning their bases with the chalk line and using a spirit level to keep the blocks plumb. Stretched between each pair of corner blocks, a string line helps align the remaining blocks in the course. To set the line, I attach it to a pair of line blocks and hook the line blocks over the corner leads. Tension, created by pulling the line taut, holds the line blocks in place.

As I set in place each of the remaining blocks in the first course, I align its bottom with the chalk line, its top with the mason's line, and its end with the pencil mark on the concrete. Buttering the ends of both the block I'm laying and the last block laid helps ensure that the mortar joints are fully packed. Orienting the last block in the course so that a flanged end is at the last unfilled joint creates a bigger opening that's easier to fill with mortar.

I lay the second course of block the same way, setting the corners first and then setting up string lines. When I set these blocks, the block end needs to be half of a mortar joint (about 1/4 inch) shy of the center of the web of the block below for proper alignment.

Brick Tricks

When building with brick, it's easy to correct for out-of-level conditions by making the mortar joints slightly thicker or thinner as the corner leads are built. Because the corners establish the elevation for the remaining bricks in each course and the final building dimensions, I'm careful to continually check that each one is plumb and at the right elevation as I lay up the walls.

Building Brick Corner Leads

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The author uses the edge of his trowel to quickly align the brick that he's laying with the one below.

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Then he uses a level to make sure the corner is plumb.

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When the mortar has had time to set up, he uses line blocks to hold strings.

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Because string tension can pop a freshly laid brick right out of the mortar, he sometimes runs the strings long and uses line twigs as guides.

To help space brickwork evenly, I always take the time to lay out each course, making marks with a pencil directly on the course below. This ensures that the final "closure" brick in each course fits perfectly.

Finishing Up a Brick Course

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After centering the final "closure" brick in the course, the author removes the string line.

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He then throws mud down the unmortared joint.

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He packs it full with a 3/8-inch tuck-pointer so that the head joint is completely filled.

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Then cleans up the front of the joint.

When setting brick, it's important to completely fill head joints with mortar to prevent water from penetrating the wall. To do this, I'm careful to fully butter each brick before setting it, rather than partially buttering the last brick laid and setting the brick dry. When I set each brick, I push it into place so that mortar starts to squeeze out of the head joint.

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Though partially filled head joints are all too commonly seen in the field.

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Head joints should be completely packed with mortar to prevent water intrusion. The author butters the end of each brick before setting it, then taps the brick with his trowel to compress the mortar and align the brick with his layout marks, which are marked on the course below.

Had this wall been taller, I would have needed to use additional steel to laterally reinforce the brickwork. But the only extra steel needed here was the 10-inch L-shaped anchor bolts for attaching the mudsill. I typically install the anchors as I lay up the final three courses of brick, cutting the bricks around the bolts where necessary and completely packing the space surrounding each bolt with mortar. Because three courses of standard bricks equals 8 inches, 2 inches of each bolt remain above the finished foundation for attaching the sill.

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To hold down the treated mudsill, the author installs L-shaped anchor bolts, cutting the bricks to fit around the bolts and filling any voids with mortar.

Keep It Clean

It's no fun removing dry mortar from brick, so I try to work as cleanly as I can. When cutting excess mortar from head and bed joints with my trowel, I turn the blade slightly outward, which reduces the amount of mortar that smudges the face of the brickwork. After the mortar has begun to dry in the section of wall that I'm working on, I dress the joints with a 7/8-inch concave jointer, which compresses the mortar and makes the joints look neat.

Later, if I'm working with smooth-faced brick, I'll carefully clean it off with a dry Norton synthetic steel-wool pad while the joints are still soft. The next day, I'll use a nylon pad and water to give the brick a more aggressive cleaning.

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Synthetic steel wool works well for cleaning smooth-faced brick. The author scrubs carefully with a dry pad while the joints are still soft, then gives a more aggressive cleaning the following day with water.


John Carroll is a mason and builder in Durham, N.C., and the author of Measuring, Marking & Layout.