We are often contacted by homeowners who are concerned about cracks in their properties. Recently we have inspected a number of period properties where the owners have noticed cracking around brick arches.
Brick arches are found within openings in walls, typically above windows and doors. They function to support the wall above the opening, transferring its load to the wall either side of the arch. In older properties, where the walls are of solid brick construction, the arch will either be formed of solid brickwork, or of a half-brick wide timber lintel on the inner part of the wall and brickwork on the outer part of the wall.
In all cases cracking is the result of some form of movement. Where cracking is present in or around brick arch, it may be that the movement is localised around the arch itself, or that the cracking is the result of movement elsewhere in the structure.
Movement to the bay has allowed the brick arch to drop slightly.
Movement localised around the arch may result from the failure of the arch or, if present, of its lintel. Arches and lintels may deflect as a result of minor movements within the structure which cause a loss of support to the abutments which carry their load. Timber lintels installed on inadequate bearings or which are undersized and overloaded may have settled or rotated. Alternatively, timber lintels may be subject to rot or beetle infestation, resulting in failure. Even slight movement in the arch or lintel will often result in cracks appearing around the opening. If lintel failure is suspected it will be necessary to remove the internal plaster and examine the lintel. If the lintel is severely deflected, or has been subject to rot or beetle infestation it will probably need replacing.
Cracking around brick arches is just as often the result of movement elsewhere in the structure. Openings in walls create a point of weakness, and it is at this point of weakness that movement within the structure will most often materialise. The causes of movement are numerous, and include soil shrinkage and heave, foundation failure, moisture, heat, the decay of materials, and poor construction to name but a few. In older properties, built on shrinkable clay sub-soils, on shallow foundations, and constructed of porous materials which are vulnerable to the effects of moisture and heat, a certain degree of movement is inevitable, and is, in the majority of cases, not a cause for concern.
The small cracks either side of this arch is the result of minor movement, and can easily by remedied by repointing during the course of external maintenance.
Where the cracking is not too extensive and is the result of minor movement within the structure re-pointing of the external brickwork to ensure weather-tightness is generally sufficient. In cases where the cracking is more extensive it may be necessary to provide additional reinforcement to the brickwork via the insertion of helical bars and/or to break out and replace sections of the brickwork.
Diagnosis of the specific cause of cracking can often be challenging, due to the large number of potential causes. However if you are concerned about cracks in your property our team of Chartered Surveyors are on hand to help. We can provide a bespoke report detailing the cause of the issue and the most appropriate remedial work. For further information you can give us a call 020 7183 2578 or send us an email.