Private and social housing adopted the occasional use of cavity
construction for external brickwork in the 1920s, although it only came
into common use after the Second World War. Over time such brickwork
can suffer from a range of defects, including cracking, bowing, failure
of arches and lintels over openings, and differential brickwork
movements, to name but a few. (To find out more about Cavity wall
construction history, click here)
Such defects as those
mentioned above are often attributable to a range of causes, the most
common being thermal/moisture (hygrothermal) movement, foundation
subsidence, wall tie inadequacies, changes in loading and cavity debris.
AWT
have extensive experience in the diagnosis and repair of these defects,
using both long established proven techniques and newly developed
solutions. Repairs are always undertaken with care and attention to
detail by our trained and highly skilled operatives.
Upon
instruction, AWT will undertake a building inspection (including cavity
wall tie survey) to note visible brickwork defects. We will then
prepare a clear, simple report, detailing our findings and the most
likely causations. Where applicable, the report will also provide
remedial work recommendations and a quotation or budget.
COMMON DEFECTS – CAUSATIONS AND REMEDIES
- Horizontal cracking to bed joints above DPC level
- Cause: Commonly associated with wall tie corrosion.
- Remedy: Wall tie treatment.
- Wall tie treatment – Generic repair
- Wall tie deficiencies
- Cause: Low density of ties and corrosion, together with inadequate embedment.
- Remedy: Installation of a recognised pattern of, and/or supplementary, remedial ties and, where appropriate, the isolation of old ties.
- Bowing brickwork
- Cause: Often associated with lateral restraint deficiencies.
- Remedy: Introduction of lateral restraint ties into existing
floor and roof. Often combined with the insertion of supplementary wall
ties and bed joint reinforcement.
- Failing brickwork above window/door openings
- Cause: Often attributable to inadequate support over windows (i.e. no lintels) 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.
- 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 hygrothermal movement is the cause then the
introduction of movement joints would be the most appropriate remedy.
Note:
Special care should be taken when assessing calcium silica brickwork
which has movement characteristics different from those of traditional
fired clay bricks.
- Bay window movement
- Cause: Often associated with localised subsidence and a lack of ties to the main building.
- Remedy: Tying back to main structure as a stand alone
solution, while at other times to supplement underpinning and/or
arboricultural works.
- (see Bay Window – Generic Repair).
- Brickwork dampness at ground floor level
- Cause: Mainly attributable to defective or missing damp
proof course (DPC) and/or cavity bridging with debris from original
construction. Often exacerbated by lack of adequate cavity ventilation.
- Remedy: Cavity cleaning often combined with the insertion of
a new DPC and the introduction of weep holes to improve cavity
ventilation.
- 2.2 F: Bridged Cavities – Cavity Cleaning – Generic Repair
- Spalling bricks/poor pointing
- Cause: Frost action and general erosion (but beware of crypto-efflorescence failure!).
- Remedy: Traditional brickwork replacement and re-pointing to match existing.
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: