Concrete repair techniques Flexcrete approved contractor Archives

Concrete Cill, Mullion and Lintel Repairs

The Canterbury North Control Building, part of the UK power network infrastructure, was suffering from “concrete cancer”. Cracked and crumbling concrete window cills, mullions and lintels needed specialist concrete repairs to remedy the underlying issues and prevent further deterioration.

The Problem

AWT was contracted by AMEC Foster Wheeler to provide structural repairs on part of the UK power network infrastructure. Corroded reinforcing bars within the concrete window mullions and lintels was causing the concrete to crack and crumble from within. This is commonly known as “concrete cancer”. Weathering had also taken its toll on the concrete framework around the windows and doors.

Failing lintels and mullions can cause difficulties opening and closing doors and windows as the frames become distorted. There is also a danger of injury from falling masonry. More than superficial repairs by traditional building techniques was required.

The Solution

Action Wall Ties’ skilled operatives used specialist cutting tools to cut away larger areas of damaged concrete. Specialist tools were used to scabble the remaining areas to remove layers of loose scale, corrosion and unsound concrete.

The existing steel reinforcing bars were restored by this process to a clean, bright condition and coated with a suitable steel primer to prevent further corrosion. New stainless steel reinforcing bars were installed as necessary.

The bare concrete surface was treated with a Flexcrete 842 Bonding Bridge to prepare the surface. The damged areas of concrete were then restored using Flexcrete Monomix concrete repair mortar system. The finishing touch was achieved by applying Monolevel FC, a cosmetic grade mortar, to seal the repairs and leave a smooth surface finish ready for painting.

The concrete repairs achieved by AWT’s skilled staff restored the integrity of the masonry by getting to the root of the problem. A long term solution was provided that maintained the appearance of the property.

Greater London, Essex, Sussex and Kent are all covered by the professional services of Action Wall Ties.

Action Wall Ties (AWT) are specialists in structural defect remediation, masonry reinforcement and repair, providing professional solutions to a wide variety of structural problems. Contact us on 01227 721 255, or email us.

Bowing brickwork piers and dropping arches

Victorian two-storey bay window with bowing brickwork piers and dropping arches – realignment, bed joint reinforcement beaming, lateral restraints, reinforcement to the brickwork columns and grout ties and concrete repairs to masonry cill

The subject building was a traditionally built mid-terraced domestic Victorian/Edwardian house in South London on two floors below a pitched tiled roof.

Bowing brickwork piers and cracking, dropping and sagging of the structure around the bay window required urgent attention. Using equipment and methods designed by Action Wall Ties, the bay window was reinforced and repaired.

Detailed Case Study

Defect

Action Wall Ties’ investigation reported distortion and distress with localised cracking to ground floor, external spandrel brickwork and cracking and dropped key stones to the brick arches.

The slender brickwork columns to the ground floor had bowed outwards leaving a bow shaped space between the timber box window frame and the brickwork column that has been repeatedly re-pointed.

The bay window has a very large overhanging cill with supporting corbelled knees.

Causation

Action Wall Ties reported that the movement noted was considered to be progressive due to a combination of ageing and ineffective restraining of the slender brickwork columns and rotational effect of the overhanging cills, causing the bowing out of the columns and the arches to spread, crack and drop – cracking the supported spandrel brickwork above.

Structural repair solution

Our remedial scheme involved the introduction of bed joint reinforcement beaming, lateral restraints, reinforcement to the brickwork columns and grout tie injections, together with concrete repairs to masonry cill, all to reinstate the uniformity of the wall and provide restraint.

We provided temporary support to the underside of the ground floor brick arch key stones, removed the debris from the cracks and lifted the stones/arch back into a more level line with the adjacent brickwork.

As indicated with red double dotted lines on our proposal 1, we introduced two rows of twin stainless steel corded joint reinforcement, forming a deep masonry composite beam.

As indicated with green parallel lines on our proposal 1, the beam reconnected the bay window elevational brickwork, and this was accomplished with AWT designed equipment enabling us to diamond drill through each elevation and chase into the main elevational brickwork and install a grouted helical bar.

The formation of continuous beams within the existing masonry should redistribute the upper storey loads, to a large extent, to those parts of the supporting structure, below which are best able to carry them while at the same time assisting in restraining diagonal cracking and bulging tendencies.

As indicated with yellow stars on our proposal 1, in conjunction with the beams, we drilled for, and screwed direct into the timber floor joists, 8mm stainless steel lateral restraints – all resin bonded to the masonry.

As indicated with green parallel lines on our proposal 1, to assist in alleviating the rotation affect from the large cills we installed grout ties vertically, drilling for and injecting a grouted 8mm helical bar.

As indicated with blue parallel lines on our proposal 1, we introduced a purpose fabricated steel reinforcing post, fitted and fixed to the inside of the brickwork columns, fixed with stainless steel resin bonded fixings.

Action Wall Ties (AWT) are specialists in masonry reinforcement and repair, providing professional solutions to a wide variety of structural problems in South London and Kent. Contact us on 01227 721 255, or email us.

Grade 2 listed building remedial reinforcing

Grade 2 Listed Building Remedial Reinforcing

Grade 2* listed Spa Green Estate in London EC1, designed by Bertholt Lubetkin. Extensive remedial reinforcing including work to the hit and miss vents, brick slips and widespread brickwork repairs.

Spa Green Estate is a public housing estate in central London designed by Bertholt Lubetkin and Grade 2* listed in 1998.

It is widely viewed as being the finest example of public housing of its type, but remedial works were required and Action Wall Ties were engaged to undertake elements of the project.

Extensive remedial reinforcing was required including work to the hit and miss vents, brick slips and widespread brickwork repairs.

AWT operatives were made aware of the importance of the buildings and accordingly ensured that all works were carried out with the appropriate level of care and respect for the structure, and were completed to be sympathetic with the Grade II* facade all to the approval of English Heritage.

Long Lasting Structural Repairs

The After photos in the gallery below shows the building 14 years after the work was completed. This shows the quality of workmanship provided by AWT.

SpaGreen Listed works 300x225 - Grade 2 listed building remedial reinforcing — During Remedial Work

SpaGreen Listed C1 300x225 - Grade 2 listed building remedial reinforcing — After Remedial Work

SpaGreen Listed C3 300x225 - Grade 2 listed building remedial reinforcing — After Remedial Work

SpaGreen Listed C2 225x300 - Grade 2 listed building remedial reinforcing — After Remedial Work

SpaGreen Listed C4 225x300 - Grade 2 listed building remedial reinforcing — After Remedial Work

SpaGreen Listed C5 225x300 - Grade 2 listed building remedial reinforcing — After Remedial Work

Action Wall Ties (AWT) are specialists in masonry reinforcement and repair, providing professional solutions to a wide variety of structural problems on Grade 2 Listed Buildings in Kent, Surrey, Sussex and London. Contact us on 01227 721 255, or email us.

Cracking Museum Courtyard Walls

This Grade II listed mansion in London W1 is now a national museum housing the Wallace Collection. AWT were called in to repair cracked brickwork in the courtyard walls. The brickwork repairs on this heritage building needed to provide a cost effective, long term solution while preserving the appearance of the red brick and render walls.

The subject building in central London, known as Hertford House, dates from the 1770s and features red brick and render courtyard walls.

As part of a major refurbishment cracking to the front courtyard walls was to be addressed.

Working with the main contractor and architects we proposed and completed remedial works including bed joint reinforcement, brickwork repairs and render finish repairs.

AWT used their specialist structural repair techniques to restore structural integrity without the need for visible fixings or slow, costly rebuilding work. The beauty of the red brick and render finish was preserved.

Action Wall Ties are structural repair contractors with the specialist skills required for listed buildings. AWT work along with architects, project managers and local authorities to preserve historic buildings.

AWT are available for large and small projects in London, Kent, Essex, Surrey and Sussex. To arrange a survey or to discuss project details, please use our contact form, email us or call us on 01227 721 255.

Bulging and Cracking Ornate Bay Window

This Victorian/Edwardian terraced home in Lewisham SE4 was suffering with structural defects that were causing cracks in the decorative work around the bay windows as well as bowing brickwork.

The Structural Problem

The beautiful decorative moulding around the bay windows of this terraced home in South East London was cracking. Even more worryingly, the brickwork of the bay window was visibly bulging and rotating away from the main part of the house. Inside the house there were cracks appearing in the internal party wall.

Action Wall Ties were called in to find a permanent solution to the structural issues while preserving the period features of the property.

The Structural Repair Solution

The AWT’s survey team diagnosed inadequate restraint of the bay window and a point loading issue with the party wall. Reinforcement of the masonry and a redistribution of the load on the party wall was required.

AWT have an arsenal of techniques at their disposal that are not available to traditional builders. This allows them to repair structural defects without rebuilding works.

Following a thorough survey, the following techniques were selected to restore the structural integrity:

Bed Joint Reinforcement Beaming
Crack Stitching
Grout Tie Injection
Lateral Restraints
Concrete and Brickwork Repairs

The specialist tools and equipment developed by AWT allows them to repair structural defects without compromising the look of a period property such as this.

A twin diamond bladed machine with attached vacuum was used for precision drilling prior to the installation of rows of twin 8mm stainless steel corded joint reinforcements. This helped to redistribute the weight of the upper storey to those parts of the supporting structure best able to carry them. It also assisted in restraining diagonal cracking and bulging.

8mm stainless steel lateral restraints screwed into the floor joists’ bresummer beam and resin bonded to the masonry provided further lateral restraint.

Localised cracks in the brickwork were stitched together using stainless steel fixings embedded out of sight within the brickwork.

Any patches of defective masonry were cut away and the areas were repaired using Flexcrete – a specialist repair substrate.

The finishing touches included colour matching any replacement bricks and ensuring the pointing style and mortar mixture matched the existing texture and colour.

AWT’s specialist skills allowed these serious structural faults to be repaired quickly and economically without damaging the character of the period features.

Action Wall Ties (AWT) are specialists in masonry reinforcement and repair. We provide professional solutions to a wide variety of structural problems for home owners in Lewisham and the whole of London, Kent, Surrey and Sussex. Contact us on 01227 721 255, email us or use our contact form.