Removal of corroding mild steel, Temporary support Archives

Hazardous Masonry on Grade 2 Listed Building

Listed Building with Bulging & Cracking Masonry

This Grade II listed building in Thanet, Kent, was built in the 1840’s. The owners of this period property were facing the prospect of demolition and rebuilding of the facade of the property due to serious structural defects. Previous repairs using standard building techniques had failed to solve the structural problems. The property is currently in use as a nursery school. The business would have been forced to close for several months during traditional building works. AWT were able to repair the severe structural problems in a couple of weeks and preserve the period features without disrupting the running of the business.

The Structural Problem

The structural issues with this Victorian, Grade 2 listed property in Ramsgate, Kent were becoming hazardous due to the risk of falling masonry. Traditional building methods would have required several months of expensive and messy deconstruction and rebuilding work. The business would have been forced to close during the building works and the subsequent re-plastering and redecoration.

The front of the building had clearly visible bulging and cracking to the head of all the first floor windows. There were also cracks in the brickwork and stucco works each side and to the underside soffit of the window opening heads. There were clear signs of previous attempts at repairs that had failed to get to the root cause of the problems.

grade 2 listed structural defect - Hazardous Masonry on Grade 2 Listed Building — Buckling Brickwork

As shown in the photo below, the mild steel embedded within the masonry had corroded and the rust caused it to expand to several times the thickness of the original metal. The heavily corroded wrought iron arch bars were lifting and cracking the brickwork and the decorative stucco around the windows. The stucco stringer course frieze and cornice of the parapet wall was also cracking and distorting. Previous attempts at repairs had provided a temporary, cosmetic repair but had failed to solve the underlying structural defects.

The continued expansive corrosion of the wrought iron arch bars would, without remedial works, lead to the failure of the masonry and the risk of detached masonry falling from the building. Urgent structural repairs were required.

Rusting wall bars 300x225 - Hazardous Masonry on Grade 2 Listed Building

Rusted metal grade2 listed 300x225 - Hazardous Masonry on Grade 2 Listed Building

The Structural Repair Solution

Structural repairs to listed buildings need to be handled carefully to preserve the period features of the building. AWT have many years of experience working on listed properties. AWT can help the owners of listed buildings to navigate through the process of obtaining permission for repair works.

The specialist tools and techniques that AWT employ allow structural repairs to be made without the need for visible fixings. Using custom designed drilling and cutting tools, AWT can remove corroded metal fixings and embed new stainless steel fixings within the masonry.

In order to allow the business to remain open during the structural repair works, AWT arranged for the scaffolding to be erected at the weekend while the nursery was closed. The scaffolding was then double boarded and netted for safety. The AWT crew accessed the scaffolding from the side of the building allowing parents, children and staff to access the building as usual through the main entrance.

vertical wall ties 225x300 - Hazardous Masonry on Grade 2 Listed Building — Preparing Vertical Wall Ties

grade 2 listed structural works 225x300 - Hazardous Masonry on Grade 2 Listed Building — Drilling for Vertical Wall Ties

The AWT team used their specialist techniques to form composite beams within the existing brickwork and then remove and replace the corroded wrought iron arch bars. The team then reconnected and reinforced the brickwork above the windows and the parapet wall. They also repaired the cracked decorative stucco.

Before metal grade2 listed 225x300 - Hazardous Masonry on Grade 2 Listed Building — Before – Cracks & Broken Bricks

replacement lintel Thanet Kent 225x300 - Hazardous Masonry on Grade 2 Listed Building — During – Lintel Replaced

After metal grade2 listed 225x300 - Hazardous Masonry on Grade 2 Listed Building — After – Ready to Paint

This project required a combination of:

Bed joint reinforcement beaming
Grout tie injection
Resin bonded ties
Cintec sock anchors
Removal of corroded mild steel arch bars
Replacement arch bars
Brickwork repairs

The team at AWT strive to make all works as sympathetic as possible with the existing masonry. Not only do they try to match replacement bricks and pointing for colour and style they even match the mortar mixture texture.

The high quality fixings used by AWT combined with their thorough knowledge of structural defects ensures a long term solution to structural issues.

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

AWT are available for large and small projects in Kent, London, 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.

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.

1930s style low-rise apartments with balustrade wall defect repairs

An estate of 1930s style low-rise blocks of apartments with balustrade wall defects – corroding mild steel balusters cracking masonry to half-brick thick balustrade walls – removal of the baluster embedded into the coping stone and brickwork,

The subject buildings are 1930s low-rise blocks of apartments in London, of conventional brick and filler joists construction, with open access decks and private balconies.

The Structural Problem

Cracking and dislodging of the brickwork and coping stones to the balustrade walls of the private balconies was reported and noted.

Discussion

Action Wall Ties investigated the defects and reported that the causation was found to be due to expanding corrosion of the handrails mild steel supporting balusters built into the masonry.

The corrosion of the embedded mild steel results in the formation of ferrous oxide that expands to several times the thickness of the metal it has resulted from, thus breaking out of the brickwork splitting bed joints and lifting of the brickwork.

Structural repair solution

Action Wall Ties remediation involved cutting the baluster at the coping stone line, removal of the baluster embedded into the copping stone and brickwork, and completing repairs to the brickwork and coping stone. AWT re-drilled holes down into the walls for grout and designed all the necessary stainless steel fixing plates, thereafter welding the original baluster to a fixing plate.

Action Wall Ties (AWT) are specialists in masonry reinforcement and repair, providing professional solutions to a wide variety of structural problems in Kent, London, Surrey and Essex. 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.

Cross Rail Projects Victorian Connaught Tunnel

Crossrail Projects Victorian Connaught Tunnel

AWT were the chosen contractors for the Crossrail project at the Victorian Connaught Tunnel in central London. Strengthening, pinning and pressure grouting techniques were used for this vital infrastructure project.

The Crossrail project was to breathe new life into the old Connaught Tunnel. It was built by the Victorians but was, at the time of this work, a disused brick-arched structure lying beneath London’s Royal Docks that survived a hit from a bomb during WW2. This was to be the only existing tunnel to be re-used for Crossrail. Works involved the widening, deepening, as well as strengthening, of the existing structure.

Action Wall Ties’ expertise and experience was sought to undertake the proposed strengthening works to the brickwork arches to the approach cutting, and the damaged area of brickwork rings that form the tunnel. This was to be carried out with the introduction of injected grout, grouted ties and pressure grouting areas where the brick work rings had separated, which was believed to be due to bomb damage.

In line with the Crossrail specification to reconnect the brickwork with the temporary supports in place we firstly drilled vertically 20mm holes 1000mm deep and injected cementitious grout, filling any contiguous voids. Once this was set we revisited the grout filled holes and re-drilled to 25mm for, and injected, cementitious grout and 16mm stainless steel bars simultaneously pinning the brickwork rings together.

After the completion of the pinning, in an attempt to fill any voids to complete the reconnection, we drilled a pattern of 16mm holes with the entrance counter drilled to receive injection packers, ready for the pressure grouting injection. With the pre-batched TamCrete MFC grout mixed and holes flushed with water we injected the grout up to 1 bar over injection pressure, until either hydraulic lock or venting grout from adjacent holes is attained.

Finally, AWT made good the entrance holes with concrete repair mortar.

AWT can provide cost effective structural repairs for a wide range of public sector and infrastructure projects. We operate not only in London but across the whole of the South East of England. We have many years of experience working on large projects, liaising with structural engineers and local authorities.

Contact AWT today to book a survey with one of our experienced team of structural repair specialists. Contact us on 01227 721 255, or email us.

Harrow High School. Corroded Window Arch Bars

Harrow High School. Corroded Window Arch Bars.

As can be seen in the photos, there were cracks in both the external brickwork and the internal plaster work around the windows of these school buildings in Harrow, Greater London. In places the external brickwork was crumbling.

The Structural Problem

The brickwork above the windows was visibly lifting and cracking. An inspection by Action Wall Ties quickly identified the cause as corroding mild steel arch bars which were reducing the support from the existing lintel arrangement. This type of fault also results in difficulties with opening and closing windows.

The flat brickwork arches in the building were of differing ages but all were built on mild steel arch bars. As these bars had rusted the resulting ferrous oxide (rust) expanded to several times the thickness of the original metal in turn lifting and cracking the brickwork above. In places the facing brickwork had crumbled to reveal the metalwork.

The Structural Repair Solution

The remedial works were designed to add tensile strength and reinstate the brickwork’s integrity without detracting from the appearance of the building.

The brickwork openings required remedial support and the arch bars needed to be removed to stop any further damage to the building. Bed joint reinforcement and beaming fenestration lintel repair techniques were used to restore the tensile strength of the masonry.

Bricks were carefully removed to allow the cutting and removal of the corroding arch bars. Two rows of twin 8mm stainless steel corded joint reinforcement fixings were installed forming a deep masonry beam. The formation of continuous beams within the existing masonry redistributes the upper storey loads and assists in restraining diagonal cracking and bulging.

Specialist drilling rigs were used to drill for and install helical stainless steel pins through the brick arch and into the line of the deep masonry beam that had been installed within the existing masonry.

Where possible the existing bricks were reused. Replacement bricks were colour matched to blend in with the original brickwork. The cracked mortar was raked out and repaired with new coloured sand and cement mortar to match the existing mortar.

Action Wall Ties serve customers not only in the Harrow area but throughout the South East i.e. Kent, Greater London, Sussex, Surrey and Essex.

Action Wall Ties (AWT) are specialists in masonry reinforcement and repair, providing professional solutions to a wide variety of structural problems including issues with window arches. Contact us on 01227 721 255, use our contact form or email us.