Our house is 60 years old, clay bricks in lime mortar. Took down part of the inner leaf during alterations and discovered that the butterfly wire wall ties are rusting, but I still had a helluva job snapping one when I tried to get it out of the outer leaf. Anyone have any photos to illustrate the stage at which the ties need "replacing"?
Its good that the tie was still strong. If it wasn't you could have a big problem.
Wall ties hold the outer wall to the inner wall. The roof usually sits on the inner wall. When the wall ties fail in sufficient numbers the outer wall becomes unstabel and can fall away (collapse) Once wall ties start corroding they are considered to be in need of replacement. It seems extreme to install a new stainless steel system when you cant see any physical damage however it is a cheaper option than waiting and having to rebuild the wall.
No one will give you a definate time scale as to the remaining life of the tie.
The best thing you can do is find a reputable contractor and ask for a wall tie condition report. You could also ask a structural engineer.
Over the years there have been many varieties of wall tie, the earliest were made of cast iron, subsequent ones mild steel, later they were galvanised and today are stainless steel.
The early mild steel were inclined to rust and lift up the rows of bricks letting the wind blown rain in and once rusted through the suction effect of the passing wind could pull great chunks of the walls out.
Take a careful look at yours, they may be galvanised, all be it the one you removed is showing signs of rust.
Getting someone to locate each one and remove and replace will cost a lot.
Thanks for the advice fellas. The ties are definitely the old galvanized wire type and I am told that even they fail they don't need to be removed, or even isolated. As the walls aren't deformed or anything at the moment it's just a case of deciding whether to do the job now, as a precaution, or whether it can be deferred a few years. We have just had a rewire and all the walls are stripped, so I'm thinking we could have it done from the inside. Think I'll speak to neighbours whose house is on the market and ask whether any surveyors have picked up on it. Thanks again.
1. you post reads like it is the wall tie bedded into the inner skin that has rusted. Is this correct, or is it rusting where you can see it abutting the outer skin.
2. Perry525 is correct in stating that the corrosin of mild steel wall ties can result in horizontal cracking externally, however such cracking is unlikely to occur with the butterfly type you have suggested, only the thicker MS fish tail ties.
3. Finally, prior to 1981 the galvaniting on wall ties was insufficent. This was found after many failures in 1950's properties using galvanised steel ties. A new British Standard was issued in 1981 specifying a much thicker galvanising thickness.