Damp in subfloor?

[hjf456]

Newbie here, so please be gentle!

I'm in the process of buying a 1920s mid-terraced house in South London. I had a full structural survey from a reputable firm who get consistently good reviews.

The surveyor highlighted damp meter readings that were '900-plus, off the scale' along the front bay window of the ground floor lounge, and then along one adjoining wall with the house next door - on which are two fireplaces about 3m apart. The surveyor used 'an Aquant electronic moisture meter'.

The whole of the downstairs has been made open plan, with an extension built in 2011 that spans the full length of the back of the house and extends to less than 3m (within permitted development).

The problem is, there is a laminate/engineered wood floor that covers the entire downstairs, so the surveyor was unable to confirm whether the original timber flooring in the old part of the house had beetle infestation, dry rot or other.

What he did note is that there are no visible air bricks out the back of the extension (though decking protrudes directly from the extension so it may be hiding them). The surveyor's concern was the extension was built without any adequate subfloor ventilation or air bricks, and therefore the original part of the house has air coming in the front (there are two air bricks at the front of the house) but not going out the back.

I'm now in a situation where the vendors don't feel there's an issue ("we've never had a problem") and can't produce detailed plans of the 2011 extension.

The council planning website appears to show the extension was approved retrospectively (though it's hard to 100% confirm this due to the lack of detail). The vendors did not do the extension - they bought off a developer in 2011 immediately after the work. The agent is unsurprisingly backing his clients.

My surveyor says the work to remedy the 'damp' would cost £8k-plus. The estate agent had someone go round yesterday and says 'there's no damp'.

I've spent the evening reading forums about damp, and the many myths that surround it. I feel it's foolish to ignore my surveyor (who I paid over £700 to!), but also know there's a lot of backside-covering with these surveys. Getting another damp specialist round is an option, but I've read that PCA ones will only try and flog you a DPC, and non-PCA ones will charge several hundreds of pounds and would still want to take up some of the laminate flooring.

We like the house but can't afford £8k to remedy something post-purchase and would need this factored into the price.

Any advice on what to do next would be gratefully received. It's causing many sleepless nights for me and my (heavily pregnant) wife!

Thanks

 

[Burnerman]

For properties with suspended timber floors, lots of ventilation is essential.....more so for the older buildings with earth instead of a concrete raft.
You don't say for sure if the extended area has a suspended timber or concrete floor - is it possible to see beneath the decking?
No one can say if there's rot, damp etc without getting a couple of floorboards up......very awkward with laminate down which will almost certainly be damaged.
The damp around the bay may be aggravated by the surrounding land being too high, or splash from leaking gutters and so on.
John

 

[hjf456]

Thanks John. My assumption is that the extension has a concrete floor. The house was 'flipped' in 2010/11 by a developer, so I assume they chose the easiest and cheapest way of building it - concrete rather than timber.

The gutters that run down the bay are in good order and there is an airbrick at the foot of the bay. I was surprised there was a damp reading there.

So you feel it's a case of lifting the laminate or nothing?

 

[Burnerman]

Obviously it's dead easy to be smart sitting at a keyboard
If your extension is concrete then obviously there won't be air bricks there.....however, air still has to circulate around the suspended timber area.
I've seen this done with ducts laid in the new concrete (whether that satisfies building control I wouldn't know). With a terraced property, you can't put more air bricks in the sides, naturally enough.
Suggestions? Difficult! Personally I'd want to see below the floors, but I appreciate the seller won't like that! Just possibly a professional surveyor may be able to put a camera scope through an existing air brick and take a look around with that.
You can expect damp on hearths - no issue with that - but there could be issues with that party wall.......maybe a bridged damp course or whatever. The same could apply to the bay window.
Curious that one professional says damp, and another says no damp - not very reassuring, that one.
Let's hear what other folks have to say!
John

 

[hjf456]

Thanks. Just so I'm clear, if ducts run through concrete to carry air flow, what would I expect to see at the point the duct meets the air? I assumed the duct end would be covered by some sort of grill or vent (which to a layman like me would look similar to an air brick)?

 

[Burnerman]

Sure, if there are ducts, (and that's not certain by any means) there would be a grille of some sort to keep rodents etc out. It needs a peek beneath the deck!
John

 

[ree]

OP, it would help you if you were to post a plan view (footprint) of the house showing damp areas, air bricks and concrete floors?
It would also help if you posted pics of the front elevation and the rear elevation.

The extension (& the knock-thro?) would have been issued with Certificates of Regularisation if retrospective consent was applied for? The applicant would have a copy (where is it?), and the Council would definitely have a record of issuance. Why not google up to thoroughly understand these issues.

Ignore anything the agent says, they lie for a living. Same with the Surveyor's reviews - they write them themselves. Totally independent D&T surveyors operate in London ie. they dont do the work, they only report. But you dont really need any more reports given there will be a mortgage survey and probably some retentions.

Laminate, like render, can often be applied to cover something up.

Ventilation ducts are typically required by BCO in concrete extension floors - they are simply air bricks with duct pipes attached.

None of the above should put you off buying - London property prices will probably rise and cover all your costs within a year. No structural issues have been raised. Use all the above to beat down the asking price.

Dont "assume" anything when buying a property - verify everything and only accept written or legal copy.

 

[hjf456]

Hi Ree

Thanks for taking the time to comment.

I've uploaded four pictures of the house and a floorplan (in my albums), showing in red where the damp has been found by my surveyor. The pictures show front and rear elevations, the point where the decking meets the bi-fold doors and the internal downstairs room looking front to back. You'll see the flooring covers the entire space.

I have Googled extensively to find out if Building Control needs evidence of subfloor ventilation to approve an application, but it seems to be a grey area. I've spoken to the council who can only confirm that the application was approved, but have no more paperwork than the original pencil drawings that were submitted (which don't state the materials used).

My hope is that the decking is covering some duct vents, but it's impossible to know without breaking it up. Maybe one I have to take back to the sellers as a must-do.

The mortgage survey came back fine as the property is in good nick (on the face of it). It's more about making sure I'm paying the right price considering what I might be lumbered with underneath all that laminate...

Thanks in advance for any further insight.

 

[ree]

Thank you for the pics and plan.

Can you clarify how many surveys/reports you've had - by who? Did the mortgage survey note any damp in the walls? Did the mortgage survey concern itself with any of your above apprehensions?

What application was approved by the Council? The original extn plans or a retrospective application?

I cant see any BCO allowing the thro ventilation to be blocked off as yours appears to be by the extn slab. Get a copy of the original pencil drawing and see if ducts were detailed in it - the material is irrelevant.
AAMOI: there is a something (a grill?) in the centre of the extn floor - do you know what it is?

The laminate looks to be reasonable stuff & the floor is level, perhaps it was laid as an enhancement to the buyer and not as a cover up?

You have two knock-thro's - one between the front room and the rear room, and one thro the rear elevation.

A floor access trap might be found under the stairs or in a hallway mat well - just saying.

 

[joe-90]

If I lived in London I'd cut grooves in the concrete with a grinder when the house was empty and vent across. That will be about £300 plus materials thanks. If the laminate is click type - I'll put it back down for a hundred. Job done.

You won't find a perfect house. The vendor will simply put it back on the market. Either buy it or walk away.

 

[hjf456]

Thanks both.

I got a full structural survey from a RICS surveyor. He highlighted the damp and put a remedial price of £8,500+ on fixing it ('Management of dampness, redecoration and subfloor ventilation').

On the back of this, the estate agent got a PCA damp proofing firm round for a timber and damp report. They recommend putting in two vents at the back of the extension 'to provide adequate subfloor ventilation' (at a cost of £380). They say that moisture levels around the skirting and plaster in the ground floor 'are within the prescribed limits'. I find this slightly contradictory, and am not sure what the vents will do if there is no adequate subfloor ventilation under the extension... They get poor reviews online, btw.

There was one planning application approved, with basic drawing plans submitted that don't show any obvious ducts. There were two further BC applications - one rejected as 'work has already commenced' and one approved about 3 months later - presumably after the work had been completed. I find it unlikely the developer would have downed tools for 3 months. Hence my concern that it may have been finally approved by BC retrospectively, and after the laminate went down.

It gives me heart that you think the BCO wouldn't have signed off without proof of subfloor ventilation. I think I have to take this back to the sellers and insist we take up a portion of the decking to settle this once and for all!

What's in the middle of the floor is a tissue/cloth that must've been there on the day of inspection (surveyor's photo).

Thanks again for your help, and Joe-90, I appreciate your honesty. Useful feedback.

 

[hjf456]

Oh, and the mortgage survey didn't bring up any issues whatsoever, though from my experience (particularly in the current market) mortgage surveyors just need assurances that the property is generally safe and sound. They don't normally do damp readings, more a quick visual walk-around. The property looks to be in good condition and is in a decent area, so they obviously felt it ticked most boxes. Thanks