Common problems include cracked walls, rising damp, and failing mortar making chimneys or other structures unstable.
Where there are cracks in brick masonry walls, foundations or chimneys, the first task is to determine the cause of the cracking and if the crack is likely to get wider.
Settlement of the ground over time
With settlement, the key question is to determine if it is still occurring. This can be done by monitoring the width of the crack. If static, then the decision is whether to accept the movement that has occurred and work around it or attempt to underpin the building.
Past earthquake damage
Cracked joints may able to be repointed, and it is possible to replace bricks that are cracked. If the crack is still widening or a repair is proposed, specialist engineering advice and design is required.
Shrinkage and swelling in expansive clays
Expansive clays will always swell and shrink in response to the amount of rainfall so it is likely that these cracks will open and close regularly. While joints can be repointed, they may crack again as the clay moves.
Corrosion of reinforcing in lintel beams
Corrosion of reinforcing usually means some significant damage, which will need to assessed by an engineer. Where the damage is minor such as a small amount of spalling to the lintel, a specialist epoxy repair may be possible. Corrosion that has also resulted in cracking of the brickwork will generally require an engineered solution.
Rising damp can be a problem with chimneys (almost all bungalows had one, and many had two) and within the walls of bungalows constructed with brick.
With chimneys, the problem of the moisture can be avoided by inserting a DPC between any timber and the brickwork – it was common for original timber to be in contact with the brick, and this timber is commonly rotted and in need of replacement with new H3.2 treated material.
For brick wall construction, the problem is more difficult to remedy as the rising moisture occurs because the DPC, if inserted originally, has failed over time. A sign of moisture being present is efflorescence on the walls and/or paint bubbling from the surface. Repair is difficult because inserting a DPC into an existing wall requires substantial and progressive removal (and replacement) of bricks. One option that may give some success is the application of a proprietary waterproofing system to the face of the bricks.
The strength of any brick structure depends to a large extent on the strength of the mortar. For bungalow brickwork, a lime mortar was used. Unless this was cured slowly over a period of time, the result was a poor quality, low-strength mortar. There were no standards for producing or mixing mortars, so lime mortars were not always satisfactory.
Over time, therefore, the mortar may have failed, making the brickwork unsafe.
Even apparently sound-looking chimneys from this period can collapse in an earthquake. Removal of a chimney does not require a building consent under Schedule 1 of the Building Act. This exemption is limited to any building up to 3 storeys high as long as the removal does not affect the primary structure, any specified system or any fire separation (which includes firewalls protecting other property). Remember to check roof sarking/framing which sometimes is supported on chimney structures. Be aware also that some bracing walls rely on support from chimneys either side. Any repair work that is necessary – for example, making good the gaps left in a roof after chimney removal – can also be done without a consent. In all cases, work must still comply with the Building Code.
If the chimney is still used or the owner wishes to retain it, it could be strengthened. The most practical approach adds steel angles on the external vertical chimney corners and then 25 x 3 mm steel bands around the outside of the chimney, fastened with coach screws to the wall framing. The other option if the chimney is still in use is for the most hazardous part (above the roofline) to be replaced with a lighter weight metal flue.
Chimneys should also be assessed for fire safety if the fireplaces they serve are to be used for heating.
Other structural issues that may require assessment by an engineer include:
- previous and proposed modifications to the building, such as excavations, where walls may have been removed or are proposed to be removed
- the addition of an upper floor or part upper floor.