Remedial wall ties

[SimonJ]

Looking at buying a 1900 cavity wall house, which needs the wall ties replacing due to failure of the original ties.

I have had a quote for the work, but with no mention of removing the old ties.

The survey picked up some cracking in the brickwork, attributed to the old ties corroding and expanding.

The replacement ties will obviously bring the wall back up to strength, but if the old ties are left in, will the corrosion cause further damage to the wall?

If the old ties do have to come out, how are they removed?

[nightjar]

No. They only have to be stopped from expanding into the brickwork around them and damaging it. What happens is they drill holes through the centre of bricks for the new ties and epoxy them in place at both ends, plugging the outer part of the holes with a mix of epoxy and brick dust from the drilling. Then a chap with a rotary file in a power drill cuts the mortar away from around the existing ties, leaving a cavity around them. The holes created by this are simply re-pointed with no mortar behind the pointing, leaving the outer end of the old ties floating in a hole. The inner ends of the ties don't rust in the same way, so can be left in place.

Colin Bignell

[robgraham]

"nightjar .me.uk>"

What intrigues me is how do they know precisely where the ties are to be able to drill round them?

Rob Graham

[Andrew Gabriel]

No idea, but endoscope and metal detector probably get you near enough.

[dennis]

I would imagine they could just run a tct cutter along the mortar removing half of it and exposing the ties. Then re-point.

[Andrew Gabriel]

Sounds like a good way to have the wall collapse on you.

[meow2222]

Yes, just do it patch by patch. I wouldnt want to run into an iron tie with a coarse cutter though.

NT

[RobertL]

perhaps they locate them by seeing the external damage that their expansion is causing.

R

[Jim]

Nope. We had this done last year and they only remove small sections of pointing around the end of the corroding wall ties.

[Andy Dingley]

Same way you can tell that the cracking is caused by rusted wall ties expanding and blowing the joint, rather than any old movement - the crack pattern is quite distinctive.

If you're hacking the old ties with a 9" wheel (as used to be done), this is quite accurate enough. If you're using a cylindrical mortar rake cutter, then a simple wall stud detector is usual. These old ties are quite hefty, they're not the modern stainless steel thin wires.

[dennis]

A wall won't collapse if it has half the mortar still in the joints. They are external walls so they don't actually carry any more weight than the wall. You do it in sections anyway, just as you would do to insert a DPM.

[nightjar]

When they did my house, you could see one or two places where the bricks were spalled due to tie expansion. Brick layers follow a pattern when putting the ties in, so once you have one, you can quickly find the others by counting bricks across and rows up or down. As a final check, the chap used a hand-held metal detector, but I didn't see him get any wrong.

Colin Bignell

[Phil L]

They aren't removed, they are isolated, so when you next speak to someone about the wall ties, make sure you ask for the old ties to be isolated as your first quote doesn't cover this - expect the quote to be considerably higher.

To isolate the old ties, the mortar is cut away from them top and bottom and a plastic sleeve filled with grease is inserted over them and then pointed over.