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.

case study 56e19bd4a80183.85880495 - Grade 2 listed building remedial reinforcing

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.

case 32 a - Grade 2 listed building remedial reinforcing

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.

case 32 b - Grade 2 listed building remedial reinforcing

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.

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.

Grade I listed country house with detached bay window

Grade I listed country house with detached bay window

Madingley Hall, a 15th Century Oriel large bay window became detached – complicated diamond drilling pattern and installing Cintec sock anchors

case study 56e19bec9cf292.04166233 - Grade I listed country house with detached bay window

Madingley Hall is an elegant Grade I listed country house built by Sir John Hynde in 1543 and set in its own expansive gardens.

The hall is now owned by Cambridge University, and Action Wall Ties were engaged to undertake reinforcement works to stabilise the front bay of the building.

Over the years the Oriel bay had become detached from the main building. The internal walls of the bay were finished with oak panelling along with ornate plaster works, all of which were protected by listing in their own right.

Repairing The Detached Bay Window

case 34 a - Grade I listed country house with detached bay window

A complicated cross stitch anchor was proposed to stabilise the bay and preserve the integrity of this historic building.

Cintec Sock anchors

Action Wall Ties’ operatives diamond drilled 30mm diameter holes approximately 3.8 metres in depth and a second hole, angled off approximately 1 metre, into the masonry to meet and form cross ties to each side of the bay window at five levels.

They then prepared for, supplied and inflated the Cintec sock anchors in accordance with the specifications and manufacture’s recommendations.

This work was completed by AWT Cintec certified operatives.

case 34 b - Grade I listed country house with detached bay window

Action Wall Ties (AWT) are specialists in masonry reinforcement and repair, providing professional solutions to a wide variety of structural problems using leading edge structural repair techniques and Cintec sock anchors. Contact us on 01227 721 255, or email us.

King’s Cross Station Cintec Sock Anchors

King’s Cross Station Cintec Sock Anchors

One of London’s King’s Cross station’s main entrance brick arches was sagging and losing structural integrity. AWT was contracted by Network Rail to drill for and install Cintec sock anchors to repair the structural defect.

case study 56e19eb6768176.03107812 - King's Cross Station Cintec Sock Anchors

The subject building was central London’s King’s Cross station. This Grade I listed building’s eastern large spanning brickwork entrance arch was found to be de-bonding.

debonded brickwork bulges 1.3 - King's Cross Station Cintec Sock Anchors

case 51 a - King's Cross Station Cintec Sock Anchors

case 51 a 1 - King's Cross Station Cintec Sock Anchors

case 51 a 2 - King's Cross Station Cintec Sock Anchors

case 51 a 3 - King's Cross Station Cintec Sock Anchors

case 51 a 4 - King's Cross Station Cintec Sock Anchors

case 51 a 5 - King's Cross Station Cintec Sock Anchors

Action Wall Ties was contracted to drill for, and install, Cintec cementitious grouted sock anchors to reconnect the brickwork.

This entailed drilling 75mm holes into the 225mm arched timber frame and drilling into the brickwork with a 38mm diamond drill vertically to a depth of 1200mm. We then prepared for, supplied and installed cementitious grouted sock anchors with grade 304 stainless steel M12 threaded bar washer and nut.

case 51 a 6 - King's Cross Station Cintec Sock Anchors

case 51 a 7 - King's Cross Station Cintec Sock Anchors

Action Wall Ties (AWT) are experienced structural repair contractors with the capacity to work on both large and small public sector and infrastructure projects. We can assist with a wide range of structural repairs including the installation of Cintec cementitious grouted sock anchors.

AWT are available for contracts in London, Kent, Essex, Surrey and Sussex. Please contact us via our contact form, by email or call 01227 721 255.

Cavity Wall Construction History

Cavity Wall Construction History

This overview of the history of cavity walls looks at how the use of cavity walls started. It also looks at some of the problems that property owners need to be aware of and how AWT can help to solve these issues. Read on to find out about:

  1. Development of Cavity Wall Construction
  2. Wall Tie Corrosion
  3. Wall Tie Life Expectancy
  4. Wall Tie Damage by Corrosion
  5. Modern Wall Ties
simple horizontal - Cavity Wall Construction History
case 54 d - Cavity Wall Construction History
case 54 c - Cavity Wall Construction History
Masonry Damage from Corroded Wall Ties
Cracked Bricks from Failing Wall Ties
 
simple horizontal - Cavity Wall Construction History

Development of Cavity Wall Construction

Cavity wall construction has almost entirely replaced solid wall construction in the United Kingdom. It evolved in the latter years of the nineteenth century and became common in dwellings in northern and western Britain in the early 1900s.

Its widespread adoption as virtually standard in the construction industry happened throughout the building booms of the 1920s, ‘30s and ‘40s.

The gallery above shows the typical outer leaf (the external brickwork) of a cavity wall and the type of damage often associated with failing cavity wall ties.

When identifying whether a wall is of solid or cavity construction, something to be aware of is that the presence of headers in the brickwork (bricks laid with the smallest side facing out) is not always indicative of solid brickwork.

From the mid-1940s to the mid-1950s, “snapped headers” were often used in cavity wall construction to emulate the English bond brickwork pattern that was common in solid brickwork.

Action Wall Ties can help identify whether your property has cavity walls or solid brickwork and diagnose the underlying cause of structural defects.

In the early years, the skins of these cavity walls were held together by metal ties made from cast or wrought iron, mild steel or copper.

Wall Tie Corrosion

The corrosion of wall ties was first officially recognised in the 1960s in South Wales. At first, it was thought to be due to a combination of poor tie protection and exposure to the elements. Time has shown that many of the early ties and mortars were just more susceptible to corrosion.

Mild steel ties initially were either left unprotected or given a bitumen coating, but in the early 1930s zinc coatings or galvanising became accepted.

old corroded wall ties - Cavity Wall Construction History

The most common type of mild steel ties (under BS 1234) are strip ties (commonly known as vertical twist or fishtail) and wire ties (commonly known as butterfly or double triangle). The photo shows a range of traditional wall ties, all of which are prone to corrode and fail over time. In contrast, modern wall ties are carefully designed for strength and durability.

Wall Tie Life Expectancy

It is very difficult to predict the life expectancy of ties used in the construction of houses before 1945.

However, it can be fairly accurately predicted for those built between 1945 and 1964 :

  • Strip ties will probably last somewhere between 31 and 61 years
  • Wire ties will probably last somewhere between 15 and 31 years.

The expected life of ties used in construction between 1964 and 1981 is estimated at:

  • 23 to 46 years for strip ties
  • 13 to 26 years for wire ties.

ALL mild steel wall ties will eventually corrode – the only question is when!

As shown in the photo, Action Wall Ties can survey cavity wall ties by drilling small inspection holes and using an endoscopic camera to assess the wall ties. Contact us to arrange a wall tie survey.

case 54 a e1642420655249 - Cavity Wall Construction History

Wall Tie Damage by Corrosion

The key here is catching the problem as early as possible. If the symptoms are recognised before deterioration has progressed too far, the walls may be re-stabilised rather than needing to be re-built.

Old ties must be located using an electronic detector and replaced with a suitable corrosion-resistant remedial fixing.

Finally, existing ties will need to be isolated to prevent further damage to the outer leaf of brickwork. Corrosion of a tie within the inner leaf of a cavity wall is unlikely to become significant as they are embedded in a dry environment.

AWT’s specialist equipment allows them to isolate failing wall ties and install remedial wall ties with minimal disruption by working from the outside of the building.

Ferrous oxide (rust) will result when embedded mild steel wall ties corrode. This will expand to several times the thickness of the metal it has resulted from, often breaking through the outer leaf of the brickwork (sometimes splitting the bed joints) and causing either lifting or bowing of the walls and damage to internal finishes.

simple horizontal - Cavity Wall Construction History
rusty wall tie repairs kent - Cavity Wall Construction History
wall tie 1 - Cavity Wall Construction History
wall tie 2 - Cavity Wall Construction History
wall tie - Cavity Wall Construction History
rusted wall tie - Cavity Wall Construction History
rusted wall tie1 - Cavity Wall Construction History
Rust Damaged Wall Tie
Rusty Wall Ties
Failed Wall Tie
Crumbling Wall Ties
Rusted Wall Tie
Corroded Wall Ties
 
simple horizontal - Cavity Wall Construction History

From a structural perspective, this leaves the wall vulnerable to vertical and wind loads, especially in the case of large gable and unreturned walls. The instability of the wall will eventually result in the ties corroding away completely, necessitating the rebuilding of the wall. The gallery shows how corrosion causes the cavity wall ties to lose strength and eventually crumble away.

Modern Wall Ties

As shown below, Action Wall Ties uses a range of modern cavity wall ties that are far superior to traditional wall ties. Using their many years of experience, AWT selects the most appropriate remedial wall tie style for each project.

remedial stainless steel wall ties - Cavity Wall Construction History

There are 3 main types of replacement wall ties:

  1. Mechanical
  2. Helical
  3. Resin or grout bonded

All AWT’s replacement wall ties are made from high-grade stainless steel. They are designed to restore structural integrity and provide a long lasting solution to cavity wall tie issues.

Equipment designed by AWT can also realign brickwork that is bulging and bowing due to failing wall ties before installing new wall ties and lateral restraints.

Kent based Action Wall Ties (AWT) are specialists in wall tie surveys and replacement, providing professional solutions to a wide variety of cavity wall problems. We serve domestic and commercial customers, local authorities, housing associations and insurance companies across London, Kent, Essex, Sussex and Surrey.

Contact us to discuss your requirements or book a survey on 01227 721 255, or email us.

 

Structurally Unstable Period Property

Structurally Unstable Period Property

Victorian / Edwardian property in Harrow, Greater London, saved from partial demolition and rebuild.

case study 58dd0a549b8da4.65274980 - Structurally Unstable Period Property

This period property in North West London was saved from partial demolition and rebuild by our specialist structural repair techniques and solutions.

The Structural Problems

Slender brick columns between the front windows were severely bowing outwards.

The masonry above the windows was dropping and sagging. The gable wall above was leaning inwards and had started to collapse.

Bowing brick columns 4 - Structurally Unstable Period Property

There was evidence of previous attempts at repairs by traditional builders.

The building had been deemed structurally unstable and was unoccupied. Standard building contractors has proposed demolishing the affected areas and rebuilding. This process would be lengthy and costly.

Demolition and rebuilding would have destroyed much of the ornate brickwork and altered the character of the property. A partial rebuild of the property would also have entailed removing all the internal finishings from the affected areas which would add to the costs.

Click on the gallery below to see how far out of alignment the brick columns were.

The brick columns around the windows of this Victorian / Edwardian property had rusting metal fixings within the brickwork. This is a common cause of cracking and bowing in brickwork.

The slender support columns were visibly bowing causing structural instability in the brickwork above.

The brickwork of the gable above was leaning in and was only being held in place by the internal roof rafter. Some of the brickwork had collapsed inwards leaving a hole in the wall.

Apex 4 - Structurally Unstable Period Property
After

Structural Repair Solution

Specialist equipment designed by Action Wall Ties was employed to firstly retain the columns to allow the removal of the corroded fixings and debris then realign the columns back to inline before installing new stainless steel fixings to reinstate the structural integrity of the masonry.

Specialist hydraulic rams developed by Action Wall Ties were used to gradually realign the thin brickwork columns. Custom made stainless steel fixings were then installed to strengthen and stabilise the masonry.

Replacement bricks, where necessary, were colour matched to the existing bricks. In areas where the mortar was disturbed repointing was carried out using colour matched mortar.

Long Lasting Structural Repairs

The precisely targeted repairs carried out by Action Wall Ties preserved the decorative brickwork of this Victorian / Edwardian property. The repair works were substantially cheaper and faster than the proposed rebuild. In contrast with rebuilding, the precision techniques used by Action Wall Ties left the internal finishings of the property virtually unscathed.

Action Wall Ties offer structural repair services to period properties for clients in the South East – in London & in Surrey, Kent, Sussex & Essex.

Action Wall Ties (AWT) are specialists in repairs to period properties with bespoke solutions avoiding the need to demolish and rebuild. We also offer professional solutions to a wide variety of structural problems. Contact us on 01227 721 255, or email us.

Bowing and Bulging Wall

Bowing and Bulging Wall

The joint owners of this 4 storey semi-detached Victorian villas (converted into flats) reported visible bulging, dropping brickwork arches to the rear and gable solid brickwork walls and long cracks developed internally.

case study 5b62f1ba37a455.34142644 - Bowing and Bulging Wall

The Structural Problem

The Action Wall Ties surveyor inspection identified ineffective and inadequate restraining plus spreading of the of the brick arches as the root cause of the problem. This had allowed the main elevation brickwork to bulge outward and brick arches over the doors and windows to spread and drop causing the brickwork above to crack. It also caused long cracks in the internal plaster work of the flats.

Bronsbury front view - Bowing and Bulging Wall

This is a common problem with properties of this type and age. As well as damaging the structural integrity of the property it often makes doors and windows difficult to open and close as the frames are warped by the pressure of the sagging brickwork load above.

Restoring Structural Integrity

The introduction of remedial reinforcement to the masonry and lateral restraints was recommended to provide restraint and support to restore the brickwork’s integrity.

Specialist equipment developed by Action Wall Ties was used to install bed joint reinforcing beaming, stainless steel lateral restraints and pins within the structure of the property. This restored the structural integrity of the masonry without the need for any visible restraints.

The cracked mortar was raked out and repaired with new coloured sand, lime and cement mortar that was a match for the existing mortar’s colour and texture.

Action Wall Ties’ specialist knowledge allowed them to restore the property’s structural stability without the need for costly rebuilding work. Their specialist equipment also minimised the disruption for the residents.

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

Action Wall Ties serve customers in North West London and the whole South East of England.

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