Concrete frame building repairs to infill walls Archives

Concrete Frame Remedial Works

Inspection of this 9 storey concrete frame tower block revealed serious defects in the previous remedial works by another company. AWT installed remedial head restraints and wall ties to restore structural integrity.

The Structural Problem

This circa 1970s nine storey social housing apartment block in Dagenham that was over clad some two years previously with a polystyrene insulation system, that was deemed unsafe and removed to be replaced with PermaRock mineral Fibre EWI system. AWT was contracted to undertake an intrusive inspection of the wall ties, head restraints and visible concrete elements.

This concrete framed building’s cavity infill walls rely on wall ties to provide a degree of interaction between the two leaves, increasing vertical load and resistance to lateral movement (generally wind load) than two leaves acting separately and head restraints to tie the inner and outer walls to the concrete frame. Sound, correctly installed wall ties and head restraints are vital to the structural stability.

The British Standards Institution and the Building Research Establishment Specification Digest provide clear guidelines for the fitting of wall ties and head restraints in concrete framed buildings. Not only must the appropriate type and size of wall tie and head restraint be fitted but the number of fixings per square metre and the pattern of fixings within the masonry must also be considered.

Our Structural Repair Inspection

The AWT inspection comprised a limited inspection of the existing wall ties by drilling 12mm holes in the outer leaf of the brickwork to view within the cavity using an Endoscope. A metal detector was used to establish the remedial wall tie density and distribution and condition.

Our inspection revealed the original wire butterfly wall ties were in poor condition and found to be over their useful lifespan. Many of the original wall ties were also incorrectly installed or not embedded at all.

The remedial wall ties installed to replace the original butterfly ties were installed poorly and with insufficient population. Insufficient or incorrectly fitted head restraints dramatically reduce the load bearing capacity of the brickwork. If wall ties are broken, missing or incorrectly fitted this can allow the masonry to bow and crack.

The remedial wall ties were installed in an erratic pattern rather than the recommended pattern for maximum load capacity. The majority of the remedial wall ties had been installed in the mortar bed joints rather than into the bricks. The wrong length of ties had been fitted and insufficiently resin bonded. Many of these wall ties could be removed by hand!

The head restraint fittings were also incorrectly fitted with many being too long and protruding out of the brickwork rather than being securely fixed within the masonry.

The Structural Repair Solution

AWT provided high quality remedial work that is designed to last. Our skilled operatives take pride in their work and are committed to ensuring that every project they complete is safe.

High quality remedial ties were carefully installed in the correct pattern and density. Head restraints were also fitted to restore structural integrity.

AWT provide cost effective, safe remedial repairs to concrete framed buildings throughout London and the South East.

To book a time for one of our surveyors to visit your property, call us today on 01227 721255, email us at enquiries@actionwallties.co.uk or use our contact form to get in touch.

Eight Storey Concrete Frame Block with Bowing Brickwork & Brick Slips Movement

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.

Discussion

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.

C1 300x225 - Eight Storey Concrete Frame Block with Bowing Brickwork & Brick Slips Movement

C2 300x225 - Eight Storey Concrete Frame Block with Bowing Brickwork & Brick Slips Movement

C4 300x225 - Eight Storey Concrete Frame Block with Bowing Brickwork & Brick Slips Movement

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.

1980s Office Building with Failing Brick Slips

Imposing 1980s quadrangle designed head office building in Essex with failing brick slips. The contract for remedial fixing of the brick slips was awarded to Action Wall Ties.

The subject building was an imposing 1980s quadrangle design commercial head office building, over four floors, in four wings with entrance towers to each corner.

This building was undergoing a major refurbishment for new occupants Cofunds when some detached brick slips were noted. Action Wall Ties was invited by Como Interiors to undertake an inspection of the brick slips and any associated defects, and to report our findings and recommendations.

Action Wall Ties inspected Mayland house building, identified the defect, reported on our findings and recommended AWT designed fixing of some 20,000 brick slips.

Action Wall Ties was instructed and successfully completed the fixing of 20,000 brick slips to this building on budget and on program. Our work met with the approval of both Como and Cofunds.

The Structural Problem

The building was found to be of concrete frame construction, with cavity brickwork infill walls, an external skin of stretcher bond reddish multi-stock bricks constructed on each concrete floor beam with brick slip facing, and with windows up to the underside of the floor beam above in-between brick clad columns.

The external brickwork infill walls were found to be supported on the floor beam by approximately 60mm, with 50mm protruding to accommodate finishing and with brick slips bedded in front of the concrete floor beam, thus giving the appearance of brickwork. To each wing the brick slips formed a full brick soldier course with three courses of stretcher bond to the return wall and the entrance towers.

Since this building was built the concrete frame had shortened, and the bricks’ first irreversible expansion had taken place. We believed that these movements, together with thermal movement, had resulted in the sand and cement bedding mortar becoming detached from the concrete floor beam. Any further movement within the brickwork, and/or erosion/deterioration of the pointing mortar, could un-lock the brick slips allowing them to become dislodged and fall. Present-day practice is to mechanically fix all brick slips.

The Structural Repair Solution

Action Wall Ties have considerable experience in remediating brick slip defects and have developed methods and equipment to enable the successful fixing of brick slips in situ, avoiding damaging (i.e. cracking with impact hammer type drills) the delicate brick slips. With specially sharpened drills, developed to enable rotary drilling of the slips to complete the fixing, we inserted a special colour matched epoxy putty into the pre-drilled hole then drove a stainless steel fixing into the epoxy putty to fill hole, providing not only a mechanical fixing but bonding all the elements together. We then made good and sealed the access hole with coloured epoxy putty.

Action Wall Ties have developed a unique approach to fixing brick slip issues on low rise and high rise concrete frame buildings. Using their specialist drilling techniques and carefully designed fixings, AWT can repair brick slip defects in an economical manner that maintains the appearance of the building and minimises disruption.

Kent based AWT provide their expertise to customers in Kent, Essex, Sussex, Surrey & London. To arrange a survey or to discuss your project, please call us on 01227 721 255, email us or fill in the contact form.

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.