Wall Tie Replacement
Reason for Wall Tie Replacement
It must be stressed that wall tie failure or cracking of the outer leaf of a domestic property is rarely an immediate threat to safety of the occupants. This risk is greater to pedestrians and adjacent property and measures must be taken to restrict access to the risk areas if serve wall tie failure is diagnosed.
Wind suction in gale conditions is the normal cause of collapse of the outer leaf walls with the gable top being the most vulnerable area. Attention should be given to narrow unreturned walls such as those between openings and to the very large areas of walling such as gables. With the increase in a wall height by rust lamination of wall ties it is possible that the load bearing characteristics of a structure may change. The outer leaf of a wall may become load bearing with the resulting distortion of a roof structure.
The installation of wall ties in an existing property may be needed to:-
- Stabilize a cavity wall damaged by corrosion of vertical steel twist ties
- Stabilize a cavity wall rendered unsafe by the loss of wire wall ties by corrosion.
- Increase the number of wall ties in a cavity walls constructed with insufficient ties.
- Tie back existing cladding walls to concrete, steel or timber frame structures.
- Stabilize two parallel single leaf walls with space between not exceeding 25mm, tied together with solid mortar, where leaves are separating.
- Tie new walls or bulging walls back to existing cross walls.
- Tie wall s either side of cuts made for insertion of openings or movement joins.
Signs of Wall Tie Failure
Horizontal cracking at regular intervals, normally every five to seven courses and frequently this will be evidenced by re-pointing resulting in wide joints. The metal detector will confirm the presence of wall ties along these joints.
Outward bulging of brickwork may indicate wall tie corrosion. The inner leaf of the wall, being more firmly tied into the construction, is less likely to move with the rust lamination of the wall ties than the outer leaf. This outer leaf may lift at the horizontal cracks, and/or be forced outwards.
A pagoda roof effect may be seen at gable ends where height expansion of a gable wall has caused the roof to lift. Misalignment of slates at the roof verge is an indicator.
Lifting or sagging of lintels and sills can indicate wall tie corrosion.
Internal wall tie defects.
Window reveals show positive movement between the frames and the plaster work or uneven depth of reveal where gaps have been filled prior to decoration.
Cracked corners are visible at the point internal walls abut external walls. Watch for outward movement of the outer wall that has been camouflaged by decoration but a spirit level will confirm the lean of the outside wall.
Cracking may be visible at the wall ceiling joint.
Stair strings and skirting boards may separate from the walls. A tell-tale paint line on the floor boards may indicate board has moved with the wall and not necessarily separated.
In extreme cases horizontal cracking may be visible or decorations may show ridges at 450mm intervals.
Wall Tie Replacement Survey
Wall tie corrosion is a big problem affecting Period houses today. This type of corrosion causes numerous building issues, trapped moisture in poor exposed mortar joints. The signs of these faults could be external bricks cracking and lifting mortar beds.
Our surveyor will be happy to attend and give on sight advice and a written report if required for a Mortgage on the condition of a property’s wall ties.
Wall Tie Replacement Service
Wall tie corrosion is a common problem in properties built prior to 1960. Wall ties represent an important support in cavity walls i.e. walls constructed with a cavity between the inner skin (load bearing skin of masonry), and the outer skin (weather shield). The outer skin is normally extremely thin in relation to its height so without support, would be subject to damage by wind.
The installation of metal ties during construction provides the support for the outer wall. However, unless the ties are manufacture from stainless steel or very heavily galvanized mild steel, the ties are prone to rust making the wall more vulnerable and occasionally causing brickwork to bow.
Mild steel ties regrettably have a shorter life than the brickwork in which they are imbedded and during the life of the building, may need replacement with stainless steel wall ties which, because they do not tend to rust, will ensure a permanent solution. From 1945 cavity wall construction became normal for houses and many other buildings.
A number of documented cases of cavity wall distress attributable to wall tie failure have occurred in Britain and it is now predicted that the issue could potentially affect all cavity wall structures built before 1981, some 10 million dwellings.
Free wall tie advice from the South’s leading wall tie replacement specialist; Pam ties approved wall tie installers, with proven wall tie installation expertise.
Be Dri Customer Service
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