What is a wall tie?
An essential component of cavity wall construction, wall ties are used to connect the inner load bearing leaf to the protective outer leaf of a building, thereby providing structural stability. Nowadays, wall ties are typically manufactured from stainless steel due to its corrosion resistant properties, but this has not always been the case and some older buildings may include wall ties manufactured from other materials.
Why does wall tie failure occur?
Wall tie failure can happen where there has been corrosion of the existing wall ties or when insufficient or incorrect wall ties have been installed.
When a mild steel or galvanised steel wall tie corrodes, there is a build up of rust (also known as iron oxide), which causes the tie to expand in size. The resulting pressure on the surrounding masonry causes cracking in the mortar bed. Expansion in the external wall can also cause the brickwork to bulge outwards.
Poor installation during the construction phase can also result in wall tie failure. When building with wall ties, it is important to install the correct tie for the type, height and location of a building and a tie of sufficient length for the cavity.
If wall tie failure is not addressed it can lead to severe structural issues including the potentially dangerous collapse of the masonry outer leaf.
What are the signs of wall tie failure?
• Cracked brickwork (typically horizontal, or stepped)
• Bulging brickwork
• Rust stained walls
• Structural problems on similarly facing elevations of neighbouring buildings of similar age / building type
What is the solution?
Installation of remedial wall ties, followed by the removal or isolation of the existing wall ties, is the quickest and most cost effective solution to wall tie replacement. There are various remedial wall ties available, but the three most common are:
• Mechanical Expansion
• Resin / Grouted
Mechanical Expander Replacement Wall Ties
A mechanical expander retrofit tie consists of a threaded bar with sleeves which are pushed through pre-drilled holes. To create a secure connection, the ties are turned, expanding the sleeves.
Resin / Grouted Replacement Wall Ties
Resin or grouted ties are anchored into place when their resin (or grout) sets. A downside of these types of tie is that they are not suitable when cavity wall insulation has been installed.
Helical Replacement Wall Ties
Helical ties can be used in most wall tie replacement applications due to their self-tapping properties which gain fixity by cutting into the substrate when power driven, creating a secure and reliable mechanical connection.
The helical DryFix mechanical pinning and remedial tying system from Helifix requires no resin, grout or mechanical expansion. DryFix ties are simply power-driven into both leaves, via a small pilot hole, using a special attachment which leaves the tie recessed below the face leaving the masonry virtually unmarked while restoring structural strength.
In applications where the strength of the inner and outer building skins are unknown, a resin fixing is typically required. Helifix offers two helical wall tie solutions for this application – RetroTie and ResiTie. RetroTies are dry-fixed in the far leaf and resin bonded at the outer end while ResiTies are resin-bonded at both ends. For buildings with poor quality hollow inner leaf construction, grouted CemenTies may be used.
Please note: Wall tie replacement is not a DIY job and the most suitable tie should be specified by a structural engineer, surveyor or Helifix representative and work of this nature should be carried out by an Approved Installer. Contact us for more information.
Wall Tie Replacement Projects
If you think your home may need wall tie replacement contact the Helifix team who will diagnose the problem and provide an approved installer to carry out the remedial work required.