When inspecting brickwork for new builds, it’s essential to know what good brickwork should look like and understand the causes of poor brickwork. This guide aims to help snaggers recognise quality brickwork and avoid common issues. For a comprehensive resource, refer to the NHBC Good Craftsmanship Guide to Brickwork and Blockwork in New Build Homes.
Appearance Standards
According to NHBC guidelines, brickwork should be viewed from a minimum distance of 10 metres. This perspective helps in accurately assessing the overall appearance and identifying any flaws.
Several common problems can detract from the quality of brickwork. Low strength, variations in mix, and poor durability are among the most frequent issues. Ensuring proper mixing and curing of materials can help prevent low strength, while maintaining consistent proportions in the mix can address variations. To avoid poor durability, it’s crucial to use appropriate materials for the environment and exposure.
Proper practices are essential for maintaining high standards. Keeping mixers and equipment clean is fundamental. Materials should be stored correctly to avoid contamination and degradation. The mix used must be suitable for the type of bricks or blocks, their location in the building, and their exposure to environmental elements. Detailed instructions can be found in the NHBC guide. It’s also important to follow manufacturer recommendations for masonry cement and maintain consistent mix proportions throughout the project.
To minimise cracking, it’s necessary to provide movement joints in the outer leaf. For clay bricks, the recommended joint width is 16mm with spacing at 12 metres (15 metres maximum). Calcium silicate bricks should have a 10mm joint width with 7.5 to 9 metre spacing, and concrete blocks and bricks should have a 10mm joint width with 6 metre spacing. For any masonry in a parapet wall, the joint width remains 10mm, but spacing should be half the usual distances and 1.5 metres from corners, effectively doubling the frequency. The first movement joint from a return should be no more than half of these specified dimensions. Additionally, ties should be installed on each side of movement joints at 300mm vertical intervals or each block course.
Fairfaced Masonry Standards
Fairfaced masonry should exhibit a uniform texture, finish, and colour, including the mortar. Excessive colour banding should be avoided, and there should be no significant cracks or damage over 15mm in diameter. Where only one side can be fairfaced, such as in half brick walls, the other faces should be left neat and tidy.
When assessing fairfaced masonry, several tolerances need to be met. The wall should be adequately straight on plan, with a maximum deviation of ±8mm in any length up to 5 metres. In section, the tolerance remains ±8mm per storey height (up to 3 metres). Vertically, walls should not deviate more than ±8mm per storey and 12mm in total for taller walls. External reveals should have a maximum deviation of 4mm over 1 metre.
Bed joints should be straight, with a maximum deviation from straightness of ±8mm in any 5 metre section. The thickness of an individual bed joint should not vary by more than ±1.5mm from the average of the next eight successive joints. To determine if bed joint thickness is acceptable, measure and sum the thickness of eight successive bed joints, then divide by eight to find the average size. For instance, if the measurements are 11, 10, 12, 10, 11, 9, 11, and 10, the sum is 84. Dividing by eight gives an average size of 10.5mm. The acceptable range for the bed joint below these eight measured joints would be 9-12mm.
Perpend joints should not cumulatively displace in the same direction for more than five joints. The centre line of any perpend joint should generally be within ±15mm of the centre line of the next five successive perpend joints. To achieve proper setting out, perp joints in masonry panels between openings may be offset with the perp joints in the panels above and below, but the joints within the panel should not cumulatively displace.
Render and Cladding Standards
Render should be consistent in texture, finish, and colour. It should be flat, with a maximum vertical and horizontal deviation of ±4mm over a 5 metre section. It should also be free from crazing, which consists of hairline cracks generally less than 1mm deep and no more than 0.2mm wide. Some colour variation is normal due to differences in the suction of the background and the orientation of the wall. Daywork joints, patching, and other repairs may be visible but should not be unduly obtrusive. Minor localised hairline cracking is likely to occur in both traditional and proprietary render systems, but such cracking and crazing should not impair the performance of the home.
Curtain walling should be within reasonable tolerances and appearance for the materials used, with a maximum deviation of ±2mm in any storey height or structural bay width, and ±5mm overall, unless otherwise specified in the design. Similarly, rainscreen cladding should meet reasonable tolerances for the materials, with a maximum deviation of ±3mm in any storey height or structural bay width, unless otherwise specified in the design.
Brick slip cladding should adhere to the same tolerances as fairfaced masonry. For timber cladding, variation in colour is expected as uncoated timber exposed to weather can develop a silver/grey colour over time due to normal weathering.
Tile hanging should be reasonably uniform in appearance, especially at abutments. Significant variations in texture, finish, and colour should be avoided. Cast stone elements should be reasonably uniform in both colour and texture. It’s important to note that efflorescence, fungicidal growth, and colour variation may occur due to orientation, shading, and pollution. Surface abrasions and chips should be repaired according to the manufacturer’s recommendations.
For further detailed guidance, download the NHBC Good Craftsmanship Guide to Brickwork and Blockwork in New Build Homes. This guide serves as a comprehensive resource for maintaining high standards in brickwork and blockwork for new builds.