Damp damage: incorrect CWI?

Lungboy

Several years ago (I need to find out precisely how many) mum had the walls on her 30s semi filled. Recently, a bad damp problem has developed in the front corner walls. We had a damp company round this morning to have a look at it. Externally, the front of the house is lower than road level, so our driveway adjoins the house at quite a high level, tapering downwards away from the front corner. Because of this, the damp company said the insulation is sitting below ground level in the front corner as it's below the level of the drive.

Does that sound correct? If so, should the insulation company have refused to fill the wall? Do we have any comeback against the insulation company? If not, is it something claimable on house insurance as it was caused by a specific "event". Mum's freaking out about the cost of repairs so any help is very useful.

Furts

It would need a photo posted to guide folks on the problem. Even then we can only give a best guess.

In general I would say you cannot blaim CWI. This would be because the problem has only recently appeared. If it was a blatant defective situation you should have known by now.

All cavity wall insulation goes, in theory, below ground level. This would be for 75mm to 300mm typically. Hence your damp company's opinion would be open to questionning.

With regards comeback, the installation company - if they still exist, and some do not - will direct you to CIGA. I wish you good luck to get anywhere with them.

With regards an insurance claim I would say unlikely - it is probably a maintenance or fault issue which is not normal buildings cover.

Lungboy

The problem was only discovered recently due to a redecoration, but it's been hiding away for a lot longer I think. It sounds like the floorboards are rotten and possibly a joist too. I'll need to speak to the surveyor personally I think, I'm getting bits and pieces from my mum as she's old and disabled and gets muddled.

Lungboy

Exterior images to help:
http://imgur.com/GMTpLuG
http://imgur.com/IqN9fFG
http://imgur.com/6POHV6Z

Interior from a previous thread:
http://imgur.com/nEcPg3k
http://imgur.com/WvxPavm
http://imgur.com/HP83q1n

It's worse now, particularly on the flank wall.

Furts

This is a complex building detail and from a couple of photos I can only make general observations.

If you are saying the damp appears recent then it is likely to be from surface water off the drive, or blocked or damaged drains. There are two apparent gullies on the drive.

Coming on to the building detail, this is wrong. An acceptable detail would be a minimum of two courses of semi engineering bricks parallel to the drive with a dpc on top of this. Then the render would finish at this level, with a bellcast bead.

You do not have this, and your render touches the ground. This will be soaking up water which will pass around the corner to the lower levels by the door. The wet will also be passing through the wall if it is solid wall or if it is a defective or CWI filled cavity wall.

I cannot say if there is a tanking detail present, and if so, whether this is linked to effective vertical dpcs. This is because the tanking would be hidden. However render should not pass below dpc levels, and render does not usually get applied in conjunction with tanking and vertical dpcs. Hence again, this is saying that your render detailing is wrong.

Coming onto CWI, if the wall parallel to the drive is a cavity wall with CWI then this is unacceptable. Here the proviso is that some fool has not rendered down to the drive after the CWI was installed!

If CWI is present at the low level this is unnacceptable if it is capable of transmitting damp from the higher levels.

All these items need careful checking. It would be wrong to engage a damp company who are driven by profit and not proper investigation.

Lungboy

We've lived in the house for 30 years now, and it has always been rendered to the level it is now. The driveway has been in this configuration for that length of time too, although it was apparently different previously as the road to the front of the house went from a single track to a main double road. The council bought up lots of the front gardens and widened the road, meaning the driveway was steepened, all long before we bought it.

As you say, with such extensive render it's impossible for me to find there the DPC sits. I'm also fairly sure there are no airbricks to the front of the property, as the inside floor level is the same as the lower outside floor level.

The front wall and flank wall parallel to drive are cavity, and have been filled at some point within the last 10-15 years. The rendering existed at the level in the photos when the CWI was installed.

I've no idea on tanking, in fact I don't even know what it is

The damp survey was done yesterday and I'm waiting on the result. It was a free survey done by a DPC company, as I can't find any local independents and they seem to be well regarded even though they aren't independent.

Furts

Lungboy wrote: »

We've lived in the house for 30 years now, and it has always been rendered to the level it is now. The driveway has been in this configuration for that length of time too, although it was apparently different previously as the road to the front of the house went from a single track to a main double road. The council bought up lots of the front gardens and widened the road, meaning the driveway was steepened, all long before we bought it.

As you say, with such extensive render it's impossible for me to find there the DPC sits. I'm also fairly sure there are no airbricks to the front of the property, as the inside floor level is the same as the lower outside floor level.

The front wall and flank wall parallel to drive are cavity, and have been filled at some point within the last 10-15 years. The rendering existed at the level in the photos when the CWI was installed.

I've no idea on tanking, in fact I don't even know what it is

The damp survey was done yesterday and I'm waiting on the result. It was a free survey done by a DPC company, as I can't find any local independents and they seem to be well regarded even though they aren't independent.

Bear in mind that the damp company will tell you anything in order to get a sale. I have yet to find a decent reputable one. Plus the "surveyors" are sales people - not surveyors - and have sales targets to meet.

Unfortunately, if you do not know the dpc configuration, and do not know the concept of tanking, you become an easy target for the sharks who infest the damp proofing industry.

Remember "knowledge is power". And "knowledge counteracts BS!"

Lungboy

I posted the same issue over on the screwfix builders forum. 2 replies so far, both saying the drive needs digging out from the wall and let the wall dry out. I guess some kind of French drain setup would be needed afterwards.

On the issue of the surveyor, I had the same chap booked for a damp and timber survey of a house I'm buying as both the valuation report and building survey mentioned damp problems. I was expecting the worst but when I spoke to him this evening he said no specialist damp work is needed, and that standard maintenance would fix the damp that's present. He did suggest a £700 woodworm treatment though

Furts

Lungboy wrote: »

I posted the same issue over on the screwfix builders forum. 2 replies so far, both saying the drive needs digging out from the wall and let the wall dry out. I guess some kind of French drain setup would be needed afterwards.

If you have blown fibre CWI such as Rockwool or Insta Fibre or similar then this will not dry out by this means. You are almost certainly going to be wasting time and money following that route.

In addition, if water is getting into the cavity you do not know if this is the location. For all we know there could be a defective chimney, or flashing, or cracked render or a host of other reasons.

Your Screwfix advice appears flawed because you do not mention a survey and a check your existing drainage - which could also be the source of the problems.

Regardless, a French Drain is a flawed and ineffective solution.

Lungboy

The French drain was my assumption, not their suggestion. The damp surveyor said he wouldn't need to touch the drive according to mum. Until I have his report I'm only relaying info secondhand, however, tanking and creating a new air gap have been mentioned.

Here's the SF thread http://community.screwfix.com/threads/damp-hallway-simple-fix-or-comprehensive-job.169064/

Furts

Lungboy wrote: »

The French drain was my assumption, not their suggestion. The damp surveyor said he wouldn't need to touch the drive according to mum. Until I have his report I'm only relaying info secondhand, however, tanking and creating a new air gap have been mentioned.

Here's the SF thread http://community.screwfix.com/threads/damp-hallway-simple-fix-or-comprehensive-job.169064/

The gist is correct and ties in with my comments - my quote of two courses of semi engineering bricks do measure 150mm high!

However you would be foolish to renew the drive - this is a recipy for disaster. Think it through - what if your drains are only shallow, or services are present? Then look at the practicalities - running a roller or a plate compactor along the side of the house could crack up and bring down the render, or worse.

A likely but worrying scenario is the walls may not even have been built to withstand the imposed load of the drive. This is a retaining wall situation, and the house may not have been constructed to cope with this considerable loading. Indeed, I would almost say it is a dead certainty that it has not been.

Compounding this, cars are bigger and heavier than they once were, and vans more common. Your drive may have been OK in the days when a car weighed 800kg. Now 2 tonnes is common.

Hence, the drive may need renewing if it is found that it is causing the house walls below ground to collapse inwards. In that case the house walls need strengthening below the drive level. This is a substantial task and would require a detailed design and Approval.

This damage at present could show up as damp.

In this scenario a buildings insurance claim may be your savior.