Brickwork for manholes

Published by Strada Imaging on

Manholes can be constructed using different materials, e.g. concrete and even plastics. However, their raising section are predominantly constructed using brickwork, even though pre-cast concrete sections are also sometimes used. In addition, historically manholes have been constructed using bricks entirely, and the practice continues to date.

Figure 1. Block shaped bricks have been in use since 7500 BC

Bricks can be laid in different ways. Single-skinned construction, as shown in Figure 1, is often used for masonry without significant load-carrying capacity. Mortar, which is cement and sand, is used as joint.

Figure 2. Single-skin construction with bricks

Stronger structures are made of double-skin construction (Figure 3), which is also used in manholes. In this construction, the bricks can be laid in two different ways, as shown below. British standard brick dimensions are 215 mm (length), 102.5 mm (width), and 65 mm (height). A 10mm mortar joint is the standard in the UK. Given these dimensions, the double-skin construction results in a total width of 215 mm, irrespective of the brick layout, as Figure 3 depicts.

Figure 3. Bricks in double-skin formation

For manholes and their raising sections, bricks can be laid in two ways, as shown in Figure 4 and 5.

Figure 4. Brick length side facing the opening
Figure 4. Brick width side facing the opening

When it comes to manhole construction, builders and quantity surveyors first have to evaluate the area of brickwork for project valuation. In this regard, a key task is to calculate the brickwork area. This area is calculated through the brickwork width (Figure 4). Key parameters involved in this calculation are: brick laying direction, brick dimensions, and mortar thickness in the horizontal and vertical dimensions. A module within GroundApp helps quantity surveyors easily perform this calculation. Any other double-skinned construction is also supported by this module.

Later in construction, the foreman, site engineer, or buyer will need to estimate the quantity of bricks needed for material ordering. In this regard, the same manhole brickwork module within GroundApp also enables performing this calculation.