Bricklaying

Figure 1: Bricklaying

Image from Dengarden.com

This blog examines key bricklaying techniques.

First, let's start with the some of the key terms used in bricklaying:

• Header: the end face of the brick

• Stretcher: the long face of the brick

• Bed joint: the horizontal mortar joint between bricks

• Cross joint (or perpend): the vertical mortar joint between bricks

• Plumb: the vertical alignment of brickwork

• Course: a row of bricks laid in mortar

• Solid concrete block: widely used in construction and often used for internal garden walls or raised beds

• Gauge: height

• Weep hole: hole though brickwork through which water can drain

• Pointing: trowel finish given by the bricklayer to the mortar joints

Brick Bonds

Bricks can be laid in a number of different ways and the arrangements are known as bondings. The reason for bonding and not just stacking the bricks on top of each other is to evenly distribute the load that the wall is carrying along its entire length. This ensures that the wall reaches its maximum stability. The three bonds shown in Figure 2 are the stretcher, English and Flemish bond.

• A stretcher bond means the stretcher faces outwards and the bricks in a course overlap with the bricks in the course below one by half of its length. It is used for walls which are a single brick wide. The process is repeated through the full height of the wall. The perpends should be aligned, ie the joint in the 3rd course should align with the joint in 1st course one, etc. It is also known as a running bond.

• An English bond is one of the strongest bonds. It is formed by laying alternate courses of headers and stretchers and therefore can only be used for walls which are two bricks wide or more. Course 1 is stretchers and two rows thick, and the second course is headers and is one row thick.

• A Flemish bond is laying headers and stretchers alternatively on each course and can only be used for walls that are two bricks wide or more. It is not as strong as English bond. It is a suitable bond for curved walls because the radius of the curves is smaller than a row of stretcher bond

Figure 2: Stretcher, English and Flemish Bonds

Image from Dengarden.com

How Many Bricks Needed for a Wall?

The dimensions of a standard brick are 215mm long by 65mm tall by 102.5m wide. The standard amount of mortar that is applied between bricks is 10mm but this can be adjusted slightly if the actual brick sizes are slightly different.

To calculate the bricks required per square metre for a wall using a stretcher bond:

• The surface area per brick including mortar joints is:

(0.215m +0.01m) x (0.065m+ 0.01m) = 0.16875 m2

• Divide the answer into 1:

1/.16875 = 59.259, or 60 bricks per metre squared

Figure 3: Surface Area of a Brick Wall

Image from job-prices.co.uk

How Many Concrete Blocks Needed for a Wall?

The dimensions of the standard block used in Ireland are 440mm long, 100mm thick and 215mm tall.

• The surface area per block including mortar joints:

(0.44m + 0.01m) x (0.225 + 0.01m) = 0.101 m2

• Divide the answer into 1

1/ 0.101m2 = 9.9, or 10 blocks per metre squared

Figure 4: Concrete Block Wall

Image from chicagobricko.com

Concrete Block Types

Figure 5 shows images of a solid, a cavity and a concrete block. A solid concrete block has no hollow spaces. Cavity concrete blocks are hollow blocks and can only be used above ground level and can only be laid on their edge. A filler concrete block is solid, but is smaller with the same dimensions as a clay brick. Filler concrete block is mainly for making up levels in block walls, eg around window and door openings.

Figure 5: Solid, Cavity and Filler Concrete Blocks

Images from Goodwins.ie, Grange.ie and Wexfordblock.com

Lintels

A lintel (see Figure 6) is a structural horizontal support used to span an opening in a wall or between two vertical supports (Lintel, 2021). It is frequently used over windows and doors, to help support a building's structure. Lintels are generally used for load-bearing purposes, but they can also be decorative.

Figure 6: Lintel

Image from theconstructor.org

Window Sills

Window sills are the horizontal shelf below a window. Window sills should be longer than the opening on each side of the window and DPC should be fitted under the sill, along the sides, and up the back.

Figure 7: Window Sill

Image from warmliving.ie

Retaining Walls

Retaining walls (see Figure 8) are walls built to retain material such masses of water (dams) or earth (revetment walls). They can be used for create a usable bed out of a steep sloping site by creating changes in level.

Retaining walls can be constructed of brick, stone or concrete, depending upon the weight of material which has to be retained. The wall must have sufficient weight, width of foundation and be wide enough to cope with the pressure applied to it.

Since the pressure behind the wall decreases as it gets nearer the top, the wall does not have to be as thick higher up.

If there is water pressure from behind the retaining wall, the pressure can be relieved by having weep holes in the wall or building pipes through the wall to allow the water to escape.

Figure 8: Retaining Wall

Image from constructionor.com

Building a Wall

Firstly, a foundation must be laid, which will mostly commonly be a trench filled with concrete. For more on foundations, see the foundations blog.

• Check the foundation is level

• Set up a tight line, fixed to two concrete blocks at either end.

• Dry bond the first course of blocks. Dry bonding is setting out the first course of bricks dry before starting to build. It can help identify possible problems that may occur during the construction of the wall before committing to the position. Place the bricks in line along the length of the wall with a 10mm gap in between each one.

• For stability, build a pier/lead at each end. The blocks for the pier should be laid flat

See Figure 9 for an illustration of these first steps.

Figure 9: Laying the First Course of a Wall

• Starting at one end, spread a bed of mortar on the foundation approx 15-18mm thick

• Lay the first block on this bed joint.

• Using a trowel, place some mortar against the end of the first block. The joint should be thick enough (12-15mm) to allow the mortar to squeeze out when the next block is laid against it

• Check for level, the gauge and for plumb as each brick is placed in position (see Figure 10). If gauge is too big, or blocks are not plum or level, tap the blocks in the direction needed with a hammer. It is very important for the first course of all walls to be level and plumb as this sets the standard for the rest of the wall

• When all the blocks have been laid on the first course, the perps can be jointed using the jointing bar.

Figure 10: Checking for Plumb, Level and Gauge

• A lead can now be built at each end of the wall for the second course. A block is cut in half and then trimmed at each end using a lump hammer and a bolster, to make each half 215mm long (a block is 440mm long and when a block or brick needs to be cut, an allowance of 10mm for a joint has to be made). A bed joint, one and a half blocks long, is spread on the end bricks of the first course. Lay the half block first, put on a cross joint and then lay the full block. These blocks are now gauged, levelled and plumbed at the same time (Figure 11).

• When the two leads have been built, the line can raised to the 2nd course and the blocks are laid to the line using the blocks below as a guide

Figure 11: Second Course of the Wall

• The leads for the 3rd course are built in the same way as the first course, ie two blocks on flat (Figure 12).

Figure 12: Leads for the Third Course of the Wall

• The line is then raised for the third course of the blocks to be built and the process is continued until the wall is finished (Figure 13).

Figure 13: Finished Wall

Curved Walls

To build the first course of a curved wall:

• establish the striking point of the centre of the circle and mark out a curve out on the foundation using a trammel or string line (See Figure 14)

• place first course of bricks along the line of the radius in the screed (see Figure 15)

Figure 14: Marking a Curve in the Foundation

Figure 15: Checking Alignment in a Curved Wall

Two of the methods to ensure alignment are with plumbing points and using a trammel (see Figure 15).

Alignment with plumbing points

• Each brick in the first course of the curved wall is given a plumbing point, eg the middle of each brick

• These plumbing points are maintained over the entire height of the wall, thus keeping the wall plumb and the curve correct

• The wall should not be checked for plumb anywhere else except for these curved points

Alignment using a trammel

• Embed a steel rod in concrete, making sure it is perfectly vertical

• Attach a trammel to the steel rod and rotate around to ensure plumbness of wall

• For best appearance, use radial bricks (ie curved bricks). These are more expensive than standard bricks.

Curved Ramps

Circular ramps are often used on boundary walls where the wall joins a pillar, or at the end of a free standing wall to form a decorative feature. Curved ramps can be convex (curves outwards) or concave (curves inwards).

Figure 16: Marking a Convex Ramp on a Wall

Steps for setting out and building a convex ramp (see Figure 16)

• Establish the centre of the curve, or the striking point, and mark radius of the curve with a trammel

• Mark the curve

• Number the marked bricks to help remember what bricks go where and remove from wall for cutting. Take measurements in case any bricks are broken in the process of cutting them

Figure 17: Adding the Brick on Edge Capping to a Convex Ramp

Replacing the bricks and adding capping (see Figure 17):

• Cut and replace the bricks

• Build the Brick on Edge capping by laying the bricks on the edge with the header facing outwards

• The cross joints of the capping will be V shaped to accommodate the turning of the bricks around the curve

• Keep the bed joint to ca 10mm between the capping and the bed joint. To calculate the exact width of the bed joint:

  • The length of this curve is 1230mm

  • Divide by 75mm (length of brick and joint) = 17 bricks (round up to the nearest full brick)

  • 1230 / 17 = 72

  • Spacing should be 72mm, therefore joint should be 7mm (65mm +7mm = 72mm)

A similar method can be used for concave curve, but place the trammel centre point higher than the curve to mark out a concave shape.

REFERENCES:

Lintel (2021) Design Buildings Wiki (online) Available from <https://www.designingbuildings.co.uk/wiki/Lintel> [accessed 24April 2021]