Take a look at Wall Tie Replacement Guide (annimation).
There are two reasons why one might need replacement wall ties. The first is when the walls of a cavity wall structure have been built defectively. For example where the original built-in tie installation system has been incorrectly fitted, fitted with ties that are too short or fitted with ties at incorrect spacings. The second is where the original cavity tie system comprises metal connectors that fail or cause structural damage through the process of corrosion.
In both cases installation of a cavity wall tie replacement system will ensure that the outer brick facade wall is firmly anchored to the buildings inner and main structural masonry wall, allowing applied loads to be transferred and shared.
Provided that your walls are of a typical masonry cavity wall make-up, with each leaf being at least 90mm in thickness, you will need to install the remedial tying system at the rate of 2.5 wall ties per m2. Wall tie spacing should be at 900mm centres vertically by 450mm centres horizontally, in a staggered 'domino 5' pattern (PD 6697: 2010).
Areas most vulnerable to wind suction are those adjacent to open reveals (gable apexes, windows, door openings, etc.). Within 225mm of the vertical edges of an opening, unreturned or unbonded edges, and each side of a vertical movement joint, additional ties should be installed at a rate of one tie per 300mm height of brickwork.
In the unlikely event that either wall is less than 90mm thick, wall tie spacing should increase from 2.5 ties / sq. metre to 5 ties per m2 (450 x 450mm).
For wall tie replacement in brick clad timber frame construction wall tie installation should be spaced at 4.4 wall ties / m2. The density should be increased to 7 ties per square metre where the basic wind speed exceeds 25m/s (BS 6399-2: 1997 Code of Practice for Wind Loads).
Why not use our Wall Tie Replacement Calculator to establish how many ties you will need.
This will require a little DIY investigation by you. You should first check to see whether you have cavity wall insulation. If you have, you should avoid using chemically reactive resins and choose a wall tie system that uses the smallest installation bore in order to minimise any effect on thermal efficiencies. You will need to drill at least one investigation hole to each elevation and determine whether the bricks or blocks are solid (drilling rate will be constant) or whether they have perforations (drilling rate will be inconsistent).
You should ascertain the cavity width (the spacing between inner and outer walls of the cavity) by measuring the length of penetration of the drill bit when touching the surface of the inner (far) leaf and subtracting the thickness of the outer (near) wall. Refer to our Product Pages for your chosen wall tie replacement system to find out the length of the tie that you need.
As brick tying systems, they all work out about the same. The system with the lowest component costs is usually the one where installation process is the most time consuming and complex. The wall tie system that appears to cost the most is typically the easiest and quickest to install, with minimal prospect for operator error. Look out for ties that carry independant approvals for use in the building materials that make up your building structure.
All our wall tie installation systems are simple to install and can be installed by a competent DIY enthusiast, a builder or a specialist contractor. See the video below to see the speed and simplicity of replacement wall tie installation using a Twistfix helical wall tie.
Original wire type or butterfly wall ties that are embedded in a standard sized mortar bed can be left in place. They generally contain insufficient mass for any corrosion to cause structural damage to the walls. Simply installing a replacement wall tie system will restore stability.
Existing ties manufactured from steel plate, for example vertical twist fish tail ties, have prospect to expand as they corrode, forcing the brickwork apart and creating a series of horizontal cracks along tie-embedded courses. If a wall exhibits cracking running horizontally, spaced at 4-8 course intervals, the chances are that the existing ties are, or have been, corroding. The build-up of iron oxide layers (rust) results in an increase in the mass of the tie and the force created splits the brickwork along the bed-joint from one tie position to the next. In such instances it is wise to seek the advice of a Qualified Engineer to establish whether the corroding wall ties are fully expanded or are likely to expand further and cause additional distress to the wall. The Engineer will then consider whether additional works are needed to remove, structurally isolate or monitor the rusting tie irons.