14-storey concrete frame block with bowing brickwork
A 14-storey concrete frame block with bowing brickwork and brick slip failing – re-tie, brick slip fixing, introduction of remedial expansion joints
The subject building was a 14-storey block of residential apartments, believed to have been constructed in the 1960s.
Problem with the brick slips
The building was of concrete frame construction. Cavity infill walls with two rows of brick slips concealed the concrete floors, forming the appearance of continuous brickwork.
The infill brickwork walls consisted of an external skin of half-brick thick stock bricks with a 60mm cavity and an internal skin of 100mm solid clinker rich blocks. The concrete floor slab was in line with the head of the window and there were two rows of brick slips that became detached from the concrete floor and in many cases had fallen.
Structural Repair Solution
Under the direction of Conisbee’s structural engineers, AWT completed a remedial scheme – which included the replacement and re-bedding of the brick slips and the mechanical fixing to the brick slips, the introduction of remedial ties and remedial expansion joints, and general brick repairs.
Action Wall Ties (AWT) are specialists in masonry reinforcement and repair, providing professional solutions to a wide variety of structural problems including cracked, lifting and falling brick slips on apartment blocks in the London area. Contact us on 01227 721 255, or email us to discuss your brick slip repair options.
Eight Storey Concrete Frame Block with Bowing Brickwork and Brick Slips Movement
Five circa 1950/60s eight storey blocks of concrete frame construction with cavity brickwork infill walls in London SW19. Bowing brickwork and brick slips movement, due to concrete frame shortening. Repaired by some rebuilding brickwork and brick slips fixed insitu – mechanically fixed with Action Wall Ties designed method .
The subject development comprised of five circa 1950/60s high-rise blocks of flats in South West London. The blocks are of concrete frame construction with cavity brickwork infill walls below windows and full height to flank elevations.
The Structural Problem
The infill cavity brickwork walls were constructed with an external skin of LBC type bricks, 75mm to 95mm cavity, and a hollow clay pot internal skin.
The infill walls were constructed from each concrete floor beam to the underside of the floor beam above with approximately 65mm support to the external brickwork.
This left 40mm protruding to accommodate six/seven courses of 35mm brick slip bedded onto the floor beam, forming the appearance of continuous brickwork. The bricks have weathered well, with little sign of spalling, though some damaged bricks were noted.
The manufactured brick slips were 35mm thick with a bedding groove to the rear.
The brick slips were bedded down onto the last brick course of the infill wall and onto the face of the concrete beam, with sand and cement mortar up to the first course of the brick wall above (no horizontal soft joints were found).
A cast-in wire butterfly tie was uncovered that had not been bent out and bedded into the mortar as intended. Previous repairs, bulging leaning movement, and hollow and missing brick slips were all noted.
Hollow clay blocks formed the internal skin of the cavity walls constructed in-between the concrete floor/beams and columns.
The wall ties were found to be galvanised vertical twist, generally adequately bedded, clear of building debris, installed to a good pattern and of adequate density.
No head restraints were located with the last row of ties six/seven courses down from the head of the wall. No significant corrosion to the existing ties was noted.
We found that the buildings had generally performed well, including the buildings’ brickwork infill walls, with the exception of the brick slips and the head of the infill walls.
Since the buildings had been completed, the concrete used in their construction had shrunk, the concrete frame had shortened and the bricks’ first irreversible expansion had taken place.
Where brickwork and concrete frame abut these opposing stresses were putting the brickwork in compression, locking in the brickwork to the continuous brick slips to the flank walls.
This effect was further augmented by thermal expansion, especially to the south-facing walls.
Where the walls were not adequately tied the compression force had been released laterally, causing bulging and leaning of the brick slips and the head of the wall down to the first row of effective ties.
Most of the brick slips had become detached from the concrete beam, probably due not only to the compression force described above but to differing movements and poor fixing details. Modern-day standards require a mechanical fixing to each brick slip.
Long Lasting Structural Repair Solution
AWT completed a remedial scheme providing a viable repair by rebuilding sections of the brickwork and brick slips, introducing a pattern of mechanical fixings to the brick slips and angled head restraints along with a number of horizontal soft joints.
The gallery below shows the blocks 13 years after work was completed. The quality repairs by AWT are still going strong. In the long term, quality structural repairs provide better value for money than repeated, ineffectual repairs using traditional building methods.
All of our work to low and high rise blocks follows the guidelines provided by the British Standards Institution and the Building Research Establishment Specification Digest.
Action Wall Ties (AWT) are specialists in masonry reinforcement and repair, providing professional solutions to a wide variety of low, mid and high rise block structural problems.
AWT work with councils, housing associations, project managers and architects across London, Kent, Surrey & Sussex.Contact us on 01227 721 255, or email us.
Eight-storey 1960s concrete frame building in Aldershot, Hampshire. Cavity cleaning and remedial wall ties.
Cavity Wall Problems
The subject building started as a 1960s eight-storey commercial concrete frame building that was converted to 50 flats in 2004. Dampness, poor insulation and instability to the brickwork flack walls and brickwork features were constantly experienced and reported.
Action Wall Ties was instructed to engage a firm of consulting structural engineers to jointly undertake an intrusive inspection in order to establish a defects report on our findings to enable the design of a suitable remediation.
Concrete Frame Cavity Wall Repairs
Following AWT and Conisbee’s intrusive investigations a remedial scheme was developed that proposed providing temporary support at each floor beam, with AWT developed props, to accommodate the continuous removal of brickwork to clean the cavity and install a cavity tray
This was followed with the reinstatement of the brickwork, together with remedial wall ties and bed joint reinforcement to assist in supporting the brickwork.
Once the intrusive survey has been completed, remedial wall ties were installed and the areas of bridged cavity identified for cleaning to the foot of each infill wall line.
AWT are experts in repairing cavity wall ties and other common defects on high rise concrete frame buildings. We work together with housing associations, councils and structural engineers to find economical and effective solutions.
Bulging Brickwork and Brick Slips on 60s /70s Apartment Blocks
Concrete frame blocks of social housing in Wandsworth, London with clearly visible bowing to the brickwork and infill brick slip. Defective support to infill wall with cracked and detached brick slips.
The Structural Problem
The structural survey report on this South West London social housing block
The survey of these circa 1960s/1970s blocks of flats revealed, that due to a construction defect, the external brickwork had insufficient support. AWT also found heavily corroded wall ties plus a lack of weep vents and no horizontal expansion joints.
The infill wall external brickwork was originally only supported onto the concrete floor beam by less than 50mm. Where the wall had bulged outward this was reducing the support to just 30mm with the loads onto the brick-slips causing them to bulge out.
Our Structural Repair Solution
The infill wall brickwork was leaning and in danger of becoming detached. AWT promptly made the elevation floor safe (erecting a scaffold to provide access) by installing AWT’s specially developed props.
The remedial work included:
Installation of stainless steel support angles and cavity trays
Clearing debris from the wall cavities
Rebuilding the brickwork by removal, re-bedding and fixing of brick slips
Installation of stainless steel wall ties
Provision of horizontal expansion joints.
Repair and Replacement of Brick Slips
The original bricks and brick slips were reused when possible. Replacement bricks, mortar and sealants were colour matched to maintain the visual integrity of the apartment blocks.
Action Wall Ties are the apartment block structural repair specialists. Our brick slip and wall tie replacement solutions are available to clients in the South East i.e. in London & in Kent, Sussex, Surrey & Essex.
Action Wall Ties (AWT) are specialists in structural repairs to concrete framed buildings and tower blocks. From movement issues to wall tie replacement and brick slip repairs. We provide specialist professional solutions to a wide variety of structural problems. Contact us on 01227 721 255, or email us.