Cavity wall insulation and cavity wall ties mentioned in survey

[Klang180]

Hello

Just had a structural survey done on a mid terrace 1920s house we're in the process of buying. The surveyor is saying the following:

It is strongly recommended that a specialist cavity wall tie survey is carried out,
having regard to some evidence of repointing along mortar bed joints to the front wall
and the possibility of corrosion to wall ties in a property of this age. The worst-case
scenario could involve a complete remedial wall tie installation and isolation of the
existing ties.
Below is a photo of the front wall of the house as an example of what he has surmised.

So how likely is it that the cavity wall ties are in terrible condition and what sort of survey is needed to really take a look at these? Should we expect them to be corroded due to it being 100years old or do you think the recent retrofit cavity wall insulation has made the situation even worse? I am really erring between getting a survey to assess the damage or just walking away as this is one of many issues with the house and I am concerned it is just too much.

 

[JohnD]

Phone the surveyor.

An experienced local person will have seen lots of local houses built around the same time by the same builders using the same materials, so he may know of a particular common problem. Round my way houses of that age do not usually have cavities.

If there is a problem with rusty wall ties your house will not be the first.

Local builders will also know if they have been involved in repair attempts.

In marine areas salt spray can cause quite severe corrosion.

I can't see evidence of rain having run down that wall, from a faulty gutter or something.

In your photo, the bricks on the extreme right look different, as if an extension was put on the house at that point. Is it pure chance?

 

[Koolpc]

Surveyors always cover themselves even when nothing obvious is wrong!

 

[JohnD]

Yes, that's the other possibility.

 

[^woody^]

There is nothing in that photo to put a surveyor on notice of a wall tie issue.

I don't know how he's got from a bit a pointing to wall tie failure. Was he wearing red and blue with a large S on his chest and were there any x-ray images in the report?

 

[Klang180]

Phone the surveyor.

An experienced local person will have seen lots of local houses built around the same time by the same builders using the same materials, so he may know of a particular common problem. Round my way houses of that age do not usually have cavities.

If there is a problem with rusty wall ties your house will not be the first.

Local builders will also know if they have been involved in repair attempts.

In marine areas salt spray can cause quite severe corrosion.

I can't see evidence of rain having run down that wall, from a faulty gutter or something.

In your photo, the bricks on the extreme right look different, as if an extension was put on the house at that point. Is it pure chance?

Hey John, thanks for this response. I will give him a call tomorrow to discuss this issue and see if his knowledge of the local buildings have led him to this conclusion at all, or whether it is just cautiousness on his behalf.

The bricks on the right are the neighbours property, which they have had repointed far more recently than this house.

 

[Klang180]

There is nothing in that photo to put a surveyor on notice of a wall tie issue.

I don't know how he's got from a bit a pointing to wall tie failure. Was he wearing red and blue with a large S on his chest and were there any x-ray images in the report?

Haha point well made and I can see it may just be an exercise in covering his back. We paid a lot of money for this survey having been advised to go for the L3 version and now I am wondering if it was really worth the hassle? In any case this is the jusifiying remarks in his report:

With reference to the evidence of some localised repointing along the mortar bed joints at
the front, the fact that the property is around 100 years old and there is evidence of cavity
brickwork walls is such that it is possible that any wall ties present have suffered from
corrosion, if mild steel ties were used with only a fairly insubstantial bituminous coating.
Although we have not observed any obvious signs of cavity wall tie failure, for example in
the form of regularly spaced horizontal cracking along bed joints or as separation in
window reveals, the localised repointing might be disguising previous cracking. It is
therefore recommended that a specialist cavity wall tie survey is undertaken, which may
highlight the need for remedial wall ties and isolation of the existing.

 

[Klang180]

rear eleavtion

 

[JohnD]

...Although we have not observed any obvious signs of cavity wall tie failure, for example in
the form of regularly spaced horizontal cracking along bed joints or as separation in
window reveals, ...

He says he didn't actually see any signs of it.

So he just threw in boilerplate text.

 

[Klang180]

He says he didn't actually see any signs of it.

So he just threw in boilerplate text.

Thanks for that, it does doesn't it? Anything sinister about those cracks in the above pictures or the patchey repairs to the brickwork? I think overall the impression is of a house which has been neglected somewhat but we're worried it might go deeper.

 

[JohnD]

He also didn't see any obvious signs of elephants in the garden

Such as large trees uprooted, walls pushed over, big round footprints and massive droppings

But to be sure, you should consider a specialist elephant tracker to carry out a detailed survey.

 

[JohnD]

It looks to me like it might have been built with lime mortar but pointed with cement

I once had an old house, it was like that from new.

Some people say I didn't, but I did.

Modern practice is to cut out the joints with an abrasive disk, and apply the mortar with the nozzle of a gun. It seems to me to be a thorough job.
(I am not a builder). It will harden better in cloudy, drizzly weather, or you can mist it with a hose for a few days, starting the day after it is done so you don't wash it out. Hot dry sunshine is bad for new cement products.

 

[Klang180]

He also didn't see any obvious signs of elephants in the garden

Such as large trees uprooted, walls pushed over, big round footprints and massive droppings

But to be sure, you should consider a specialist elephant tracker to carry out a detailed survey.

I enjoyed this immensely and point well made.

 

[Klang180]

It looks to me like it might have been built with lime mortar but pointed with cement

I once had an old house, it was like that from new.

Some people say I didn't, but I did.

Modern practice is to cut out the joints with an abrasive disk, and apply the mortar with the nozzle of a gun. It seems to me to be a thorough job.
(I am not a builder). It will harden better in cloudy, drizzly weather, or you can mist it with a hose for a few days, starting the day after it is done so you don't wash it out. Hot dry sunshine is bad for new cement products.

Ah I see, my impression is that these older houses need lime mortar so as to 'breathe' but that may be a bit of a myth??

Sounds fairly sensible to me. I may end up asking a local expert on this matter how much it would cost and the likelihood of wall tie corrosion too.

 

[JohnD]

The surface area of the bricks is very much greater than the exposed surface of mortar.

If it had been rendered over the entire wall, that would make a difference, but it's a cavity wall with machine-pressed bricks and a DPC, so unless the gutters are spilling, no particular reason the walls would be damp. Lime mortar is softer and can accommodate a bit of movement. I can see some cracks and gaps in the mortar joints, especially round the arch, which I think need rectifying before repointing the wall. They may be very old. I haven't noticed severe cracks suggesting subsidence. Have a look at the neighbours houses as they will be similar construction.