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.
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
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
(Figure 2). 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.
Figure 2. 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
(A). Next he quickly rotates his wrist while pulling the trowel
back, leaving a uniform line of mortar (B). When buttering
bricks or blocks, he picks up about half a trowelful of mortar
(C), then gives it a good hard shake by thrusting it down and
pulling it back up sharply. This flattens the mortar against
the trowel (D) so that it will stay put when the trowel is
turned over (E).
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 (Figure 3). 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
Figure 3. 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 (A). 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 (B).
After setting the block, he throws mud in the joint until it's
full (C), then 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.
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 (Figure 4). 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
C D The author uses the edge of his
trowel to quickly align the brick that he's laying with the one
below (A), then uses a level to make sure the corner is plumb
(B). When the mortar has had time to set up, he uses line
blocks to hold strings (C). 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 (D).
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 (Figure 5). This ensures that the final "closure"
brick in each course fits perfectly.
Finishing Up a Brick Course
Figure 5. After centering the final
"closure" brick in the course (A), the author removes the
string line and throws mud down the unmortared joint (B), packs
it full with a 3/8-inch tuck-pointer so that the head joint is
completely filled (C), 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 (Figure 6).
Figure 6. Though partially filled head
joints (top) are all too commonly seen in the field, head
joints should be completely packed with mortar to prevent water
intrusion (bottom). 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 (Figure 7). 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.
Figure 7.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 (Figure 8). The next day, I'll use a
nylon pad and water to give the brick a more aggressive
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.