Wall Tie Services | damptec

Wall Tie Services

The tie in a cavity wall is used to tie together the internal and external walls (or leaves) constructed of bricks or cement blocks, making the two parts act as a homogeneous unit. It is placed in the cavity wall during construction and spans the cavity.

Cavity walls incorporating metal ties have been in use since the nineteenth century, however it was the 1930s building boom that saw the production of large numbers of cavity constructed properties. The role of the cavity is to stop rainwater from getting into the building and to provide a certain degree of thermal insulation.  From 1945 onwards cavity wall construction became the norm for domestic and commercial buildings.

How do I know if I have a cavity wall?

If you are unsure if your property has a cavity, one way to tell is to look at the arrangement of bricks: if the bricks alternate between lengthways and widthways then this is a good indication that the wall is solid.  If all the bricks in your wall are laid lengthways then this suggests that the property has a cavity wall.

The early metal ties were produced mainly from wrought or cast iron and performed satisfactorily, but in more recent years mild steel ties have been used and despite galvanising or bitumastic treatments have been found to suffer from corrosion and fail. This may result in instability of the cavity wall and the likelihood of it moving out of plumb.

Visual signs of damaged wall ties and wall corrosion

  • Vertical or horizontal cracking at regular intervals in external mortar joints.

  • Cracks in render coats.

  • Internal cracks; vertical cracks may be found at internal wall junctions and horizontal cracks appear at internal wall and ceiling joints.

  • Bulging brickwork.

Causes of corrosion

  • Inadequate protection - prior to the 1930s ties were not galvanised.

  • Substandard galvanising - the British Standard for weight of galvanising was actually reduced between 1964 and 1981.

  • Chemical action - for instance where corrosive black ash mortar has been used.

 

If you suspect that your wall ties have failed, it’s important that you get a professional diagnosis before the issue escalates.

Damptec have PCA qualified and experienced surveyors who have a range of solutions at their disposal to solve your cavity wall tie problem.

Did you know that cavity main wall construction now accounts for over half the UK building stock?

Most houses built before 1935 have solid brick external main walls. This would typically be two bricks wide with each row of bricks interlocking to form a solid 9 inch brick wall. After this time the trend, particularly from 1930 onwards, was for main external walls to be built incorporating a cavity i.e. a wall with two 'skins' and a gap/cavity in the middle. Initially, both 'skins' would have been of brick material. Later on changes in building regulations would mean that the inner 'skin' or 'leaf' was built using blockwork which resulted in improved thermal (heat retention) in the building structure.The cavity can be filled with additional insulation materials in the form of foam, blown glass fibre or polystyrene chippings/sheets to improve the thermal qualities of the wall. In order to hold the outer and inner skins together metal wall ties were inserted as the wall was being constructed. More recently metal ties have been replaced by stainless steel and plastic wall ties.

How do you know if your home, or a house you are proposing to purchase, is at risk of wall tie corrosion? If remedial treatment is needed, what does this involve and what are the costs?

The Building Research Establishment (BRE) has carried out research in this area which can be summarised as follows:

  • Some pre-1981 metal cavity wall ties are more prone to corrosion than others because the metal used often lacked protection against corrosion. Generally, the older the cavity wall tie the greater the risk.

  • After 1981 metal wall ties were better protected against corrosion and stainless steel/plastic alternatives introduced.

  • Cavity wall tie corrosion can be exacerbated by environmental factors, i.e. being close to industrial (airborne) pollution or exposure to salt air (cliff-top/seaside) will increase the risk of wall tie corrosion.

This means that cavity walls built before 1981 are potentially at risk.

This is particularly the case for properties built in industrial areas or close to the sea. Eventually, if left unnoticed/untreated, corroding wall ties will fail. The consequences are that if enough ties fail in the same part of the wall partial or total collapse occurs. Signs of wall tie failure include cracking along the brick courses and bulging in the wall.

To complicate things further, historically we have seen a variety of wall tie types used in construction. To ascertain what proportion of these are at risk of corrosion the Government commissioned the Building Research Centre (BRE) (an independent buildings research organisation) to investigate.

Wall Tie Condition Survey

Our surveys and remedial works follow the guidance as set out by The Building Research Establishment Digest (BRE) No. 329 “Installing Wall Ties in Existing Construction” and BRE Digest No. 401 “Corrosion of Metal Components in Walls” 

Our experienced and qualified surveyors will carry out a thorough survey to collect and record information about the construction of the walls and the condition of the wall ties.  We use specialist equipment such as metal detectors, cavity wall cameras and low impact drills.

Our survey includes:

Visual Inspection of the External Leaf

  • A visual inspection to determine which areas of the structure are affected by cracking, bulging and bowing.

Ascertaining Existing Wall Tie Spacings

  • metal detector is used to check if the cracking corresponds to the existence of a wall tie. This is a highly effective way of locating existing wall ties and establishing the placement pattern.

Investigating wall tie condition

  • Once the existing wall ties have been located, the surveyor inspects a series of ties by drilling a 10mm hole into the outside of the building to allow a cavity wall camera to be inserted into the gap (provided that insulation is not present).  If insulation is present then bricks would need to be removed.

Provide advice and quotation including the following information:

  • Type of construction i.e. solid brick, perforated brick, concrete block, etc.

 

  • As the role of a cavity wall tie is connecting the outer and inner brickwork or blockwork of a building to ensure that it is structurally sound, it is important that the cavity wall ties are working properly and not defective. 

 

  • Wall tie identification, with photographic evidence.

 

  • Wall tie orientation.

 

  • The surveyor can advise whether the problem can be resolved using remedial wall ties or lateral restraint ties, or whether additional work is required.

 

  • The report will then objectively identify the best and the minimum remedial measures based on the condition of the wall ties, as set out in the BRE digest table 4.

 

  • As property care experts, we believe that it is our duty to provide as much information as possible so our customers can make informed choices when it comes to repairs to their homes.

To find out more about cavity wall tie replacement, please call Damptec today on 0845 600 4404. Alternatively, you can request a property survey online.
 

Remember, with our 10 year structural TUG guarantee, you can have peace of mind that your cavity wall problem has been successfully treated by specialists.

Wall Tie replacement

If a problem with wall tie corrosion has been identified, our specialist technicians are fully trained and PCA certified to treat the problem as follows:

  • Holes are drilled into the brickwork at regular intervals conforming to the BS 5628 Code of Practice.

  • Installation of new stainless steel wall ties fixed either mechanically or with resin.

  • If the original ties have serious corrosion, then they can be removed as part of the repair programme or new ties installed around them. 

  • We preserve the appearance of your property by making drilled holes good to match the appearance of the existing wall.

 

Wall Tie Testing

We would always proof test the selected type of wall tie via a tension test to establish that the wall ties are gripping the masonry sufficiently. This is done by exerting a known force on the tie after installation.  After successful testing of the tie work can then proceed with the installation of the remainder. Such testing should continue randomly throughout the installation works.

 

 


 

 

Suspect a problem?

We are here to help. If you suspect a problem and require a survey, or need advice, please contact us for more information.

Damptec Systems Limited
Unit 45, The Clocktower Business Centre                   Company Number: 
8308861 
Works Road, Hollingwood                                           VAT Registration Number: GB 
139 5306 07 
Chesterfield, S43 2PE