Almost all such buildings constructed since 1950/55 have been built using external cavity brickwork. This brickwork usually performs quite satisfactorily if properly constructed and maintained, but can suffer from a range of defects over time. Cracking, bowing, failure over window openings, brick slip failure, dampness and spalling brick faces are the most common problems experienced.
These defects can be attributable to a range of causes, the most common being thermal/moisture (hygrothermal) movement, foundation subsidence, loading changes, inadequate restraint, cavity deficiencies and general “wear and tear” over the years.
AWT have extensive experience and expertise in the diagnosis and repair of such defects, using both long established proven techniques and newly developed innovative solutions associated with the remediation of brickwork containing embedded corroding steels. Repairs are always undertaken with care and attention to detail by trained and highly skilled operatives.
Upon instruction, AWT will undertake a building inspection (including a cavity wall tie survey in accordance with BRE 401) to note visible brickwork defects. We will subsequently prepare a clear, simple report, detailing any defects that were discovered and their most likely causation. Where applicable the report will also provide remedial works recommendations, quotations or budgets.
COMMON DEFECTS – CAUSATIONS AND REMEDIES
- Wall tie deficiencies
- Cause: Corroding or low density of ties together with inadequate embedment.
- Remedy: Installation of a recognised pattern of supplementary remedial ties and, where appropriate, the isolation of old ties.
- Failing brickwork above window/door openings
- Cause: Generally attributable to inadequate support over openings and often made worse by window replacement.
- Remedy: Introduction of bed joint reinforcement to span the brickwork over the opening and pinning of the brickwork followed by general local re-pointing.
- Failing/de-bonding brick slips
- Cause: Often poor fixing specification and/or lack of soft joints.
- Remedy: Replace and re-bed as necessary, fix slips using mechanical fixings and, as necessary, form soft joints, or complete removal and replacement with alternative material.
- Cracking in brickwork
- Cause: Often associated with subsidence and/or hygrothermal movements.
- Remedy: The introduction of bed joint reinforcement to beam over the areas affected by subsidence. This will sometimes supplement underpinning and at other times can be utilised in conjunction with arboricultural measures. If movement is due to hygrothermal forces, movement joints should be introduced.
Note! Care should be taken when appraising calcium silica bricks, which have movement characteristics different from those of fired clay bricks.
- Failing brickwork above window/door openings
- Cause: Often attributable to inadequate support over windows (i.e. no lintels) and rotation of boot lintels (i.e. a concrete lintel with a toe that appears to have no bearing onto the brickwork), and often made worse during window replacement.
- Remedy: The introduction of bed joint reinforcement to span the brickwork over the opening, pinning and general making good.
- Boot lintels – Generic repair
- Horizontal cracking to bed joints above DPC level
- Cause: Commonly associated with wall tie corrosion.
- Remedy: Wall tie treatment – Generic repair.
- Corroding embedded steel causing brickwork cracking [e.g. steels over openings]
- Cause: Moisture ingress.
- Remedy: Either exposure and treatment of the steel, or the removal of the steel and the provision of an alternative support mechanism.
- Bowing brickwork
- Cause: Often associated with lateral restraint deficiencies.
- Remedy: The introduction of new lateral restraint ties into the existing floor and roof. Often combined with insertion of supplementary wall ties and bed joint reinforcement
- Spalling bricks/poor pointing
- Cause: Frost action and general erosion [but beware crypto-efflorescence failure!].
- Remedy: Traditional brickwork replacement and re-pointing to match existing.
- Brickwork Dampness
- Cause: Mainly attributable to defective or missing DPCs/cavity trays and/or cavity bridging with debris from the original construction. Often exacerbated by lack of cavity ventilation.
- Remedy: Cavity cleaning often combined with insertion of new cavity trays and weep holes, to improve cavity ventilation.
- Cavity cleaning – Generic repair
All proposed brickwork remedial works are individually designed to provide a durable cost effective/best value repair through the introduction of stainless steel bed joint reinforcement, beaming, lintel repair, lateral restraints and resin bonded ties to reinstate continuity and structural integrity.
Case studies and generic repairs: