Cavity trays - what's that all about?

[Lobster]

Am endeavouring to sell a property at the moment - well, I've accepted an offer and the buyer's valuer has just been in and done his 'stuff'.

One issue has been raised relating to a flat-roofed extension, which I converted from an existing outhouse/porch area, by enclosing the area below the existing flat roof: Before:

surveyor has said: "The cement flashing at the junction of the kitchen roof and main wall is inadequate and will have a limited life and should be replaced in a more durable material" and "Install a proper flashing/cavity tray over the flat roof".

Bit peeved at the cement flashing issue as the property (along with all its neighbours) was built like that, there's no evidence of any deterioration of it, and no damp either. However, the cavity tray thing was new to me, and having googled a bit, it seems that by enclosing the space below the roof and converting an exterior wall to an interior one, then it's de riguer to install a cavity tray. Bit surprised Building Control never picked up on it, but there you go.

So, looks like I'm going to have to bite the bullet and do this work (especially in today's housing market). However, I'm not 100% clear what it involves. AFAICS, I need to remove the row of bricks immediately above where my black bitumen comes to, and insert a 9" DPC membrane so it curls up the inner leaf of the cavity wall - correct? And then I need to fit weep vents? Is that something like this: ? So, so you fit one of those in the vertical joint between bricks at either end of the DPC, with just the little plastic hole sticking out?

(Immediately under the DPC I suppose I should fit the lead flashing while I'm about it.)

So have I understood this correctly? Is DPC the correct material here? Any guidance mucho appreciated.

Thanks David

[Adrian]

I'm not up to speed with the technical aspects - but would another solution be to get quotes from a couple of builders and then knock that amount off the selling price ?

Saves you the hassle of doing the work on a place that you're trying to get rid of - and, in all probability, the new owners won't bother about the job until _they_ come to sell - and then only if their purchasers' surveyor picks up on it....

Sometimes seems to me that a surveyor's report is less a technical inspection and more a negotiating tool.

Just a thought... Adrian

[Mary Fisher]

...

Everything has a limited life. The surveyor's would be more limited still if he'd said that to me.

Mary

[Lobster]

Well yes I expect so; but I have no doubt it would be a sum well into three figures, for a job where materials would appear to be about 5 quids-worth; so I'm minded just to do this myself if it's a straightforward as it sounds. Trouble is, the buyer is quite jumpy - first-time buyer who has no clue about surveyors, and has been led to believe the work is urgent and Must Be Done.

Absolutely. But the way I see it, the surveyor has flagged two items as "Urgent" which the buyer wants sorting out (the other thing is the old cast iron guttering which I mentioned in another thread) and if I can DIY both of these at a cost of well under 100 quid in materials without affecting the purchase price, then in today's climate, that's a good result and I'll be happy.

Wretched surveyors though... other things he's pointed out are that the flat-slab concrete roof (as depicted in my last post) 'has been covered in bitumen-like material suggesting that the concrete is at the end of its life and needs replacing in the near future.' The reality is that the 4" slab is totally intact and watertight, but very ugly, so I slapped on some cold bitumen to make it look a bit less unsightly. The agent and I now have to convince the buyer of that, because I'm sure as hell not renewing the roof!

Then there's the wallpaper which is probably concealing cracks in the plaster (Hello?? All walls have been re-skimmed - there's no wallpaper in the house) - the kitchen units which are "generally satisfactory" (actually they are brand-new and in pristine condition); a long paragraph about how properties of this age are susceptible to failed wall-ties but that no signs were found and that the risk of failure was very small (actually there were extensive failures which were repaired about 6 years ago, as evidenced by the obvious filled drill holes in the brickwork). The joinery - "fair condition for the age of the property" (actually *all* the exposed joinery is brand-spanking new, and the property must be at least 50 years old) etc etc etc

[/rantmode] David

[Mary Fisher]

...

Just about sums it up. What are they for?

Can you not challenge the report?

Mary

[<me9]

When I built a lean to extension to the kitchen, the BCO was quite happy that I used silicone waterproofing on the wall above the new roof. That was nearly

20 years ago, and there hasn't been a problem. Possibly I ought to re-coat the wall. How long does Aquaseal66 last, and what is it's current equivalent?

[Adrian]

Aargh - bad situation ! On our previous house the surveyor failed to notice that all of the chipboard flooring in the big lounge was laid 'along' the floor joists, rather than across them. He also didn't notice that the central heating was only part-installed (radiators in-situ, but pipes not actually connected to anything....)

Great long list of tiny, irrelevant items - but missed the glaringly obvious - IMHO they're a complete waste of time !

Fair enough - you know the situation better than I

Don't suppose you have any photos of the slab before you bituminised it ? - might convince him...?

Yes - so many surveyors' reports seem to be wild speculation mixed with large doses of arse-covering - criminal, really....

Crazy situation - wonder how it all happened ??

Good luck with the sale Adrian

[Alan]

In message , Lobster wrote

What's going to happen if you don't do the work? Is the buyer going to pull out now that he has paid for the survey? Is he going to find another property that doesn't have any defects? He has probably already looked at a lot of properties and has selected yours as the best of the bunch in his price range.

Personally, if I had paid for a full survey and it had found something seriously wrong I would cut my losses and pull out. If it had found something minor, as in your case, I sure wouldn't want the seller to fix it.

[Derek Geldard]

I have a large lean-to conservatory about 18 ft. wide. it is 12 years old and no cavity trays were installed and we have had no damp problems. It must depend on the area of exposed wall over the flat roof and it's condition.That said it does look as if installing them is best practice nowadays.

Did you come across this website ?

Which might be interpreted as saying it might be best to install cavity trays but it can be good enough to do without if your existing walls are sound.

Is the new area created where the porch was now part of the kitchen and plastered ?

The surveyor's biggest concern is to make sure he doesn't end up with a law suite on his desk so reports are always conservative. We've had reports done on several local properties and they all read like an MOT test report into Deacon's "One Hoss Shay" .

In every instance someone else has come along and bought the place and are as happy as a pig in glabber after 15 years.

I think so. The builders used DPC when the replaced our windows.

DG

[fred]

In article , Mary Fisher writes

Exactly, this is a negotiation, not an ultimatum.

I would suggest a written reply (written in suitable technospeak of course) advising that the method of mortar flashing is consistent with local building practice, was passed as appropriate by the building control inspection and during the long life of the property has not resulted in moisture ingress. Similarly, the concrete slab roof shows no sign of age related degradation and the sealing with bitumen based sealant was simply to enhance its appearance and durability.

If pushed, agree to add some flashing cut into the mortar joint above the slope, dismantling the wall to install a cavity tray would be ridiculous.

I'm guessing if you hadn't painted the roof and up the wall, the surveyor wouldn't have said a peep, it just attracted his attention.

[Dave Liquorice]

To let the bank/building society putting up the money that the place is =

not going to fall down in the near future. A "Home Buyers report" or "Mortgage Valuation" surveys are not worth the paper they are printed on= IMHO. The surveyor will not go into the loft space or other voids, will =

not lift floor coverings or move furniture etc.

They list all manner of trivial "defects" to try and indicate they have =

actually done something for their =A3500+...

Not worth it and in any case the report was commisioned by the buyer not= the seller. There is no contract...

[John Rumm]

?

I think the only thing I would be inclined to do in this case would be to install a lead flashing over the transition. Rake out one of the joints, and install tuck some lead into the slot. Keep each strip no longer than 6' (to prevent expansion warping). Wedge each strip of lead every so often with a rolled up bead of lead cut from some scrap, that you tap in with a bolster. Dress it down over the gap and onto the slope of your concrete flashing. Finally point up the gap.

[Derek Geldard]

?

That's what the builders did with my conservatory mentioned in my earlier post, and also to an extension on the side of the house done many years previously.

In neither case have there been any problems.

DG

[Lobster]

Thanks John. This advice on the basis that installing the cavity tray is OTT?

Thinking I might try and see if I can get to speak to the BCO who signed off the project, and get his take on it: might get some useful ammo there.

David

[meow2222]

Well, you got 2 options: submit or object. If you object, the key is to give the potential buyer something the can see clearly with their own eyes, so they're left knowing the surveyor cant possibly have been right.

Dear potential buyer:

cement flashing... standard practice... can see it on all houses in the street etc. Yes, it will have a limited life, as does every form of flashing, but its been just fine for the last 50 years, but yes admittedly there is the possibility you may need to do some maintenance to the building at some point before you die of old age. Such is life I'm afraid.

bitumen: since the surveyor has not seen the roof under the bitumen, it does seem open to question for him to base his report on what he merely imagines to be under there. I painted it with bitumen as a concrete slab looks ugly when new, and even uglier when weathering has caused all sorts of staining and streaking. As you will notice, bitument does not suffer this problem, and still looks fine after all these years.

etc - its probably worth a shot.

NT

[Lobster]

Mm, probably I'm going for a third option: submit AND object! Partly, I think I have a stronger case against the surveyor if I agree to one or two points which I can resolve easily (like the guttering) but dig my heels in over others which are clearly bollocks, like the roof (which no way is being touched).

Regarding the cavity tray (and possibly the flashing too?) my understanding now is that the cavity tray *wouldn't* have been necessary before I enclosed the area beneath the roof, but is now - if so that's harder to defend. I certainly don't want to fit this if I can help it, but just some new flashing would be a doddle to install.

Still trying to reach my BCO to pick his brains. David

[John Rumm]

Indeed, Lead flashing is very widely used in circumstances such as this and very effective. It is also easy to retrofit. To attempt to install a cavity tray at this stage would seem overly complex.

Yup, might help.

[Andy Champ]

Last survey I had done (on an 18thC flat) he reported that the insulation on the loft was thin. We bought it anyway - that I can fix :) - only to find that the insulation was thin, *right next to the hatch where the PO kept his spare boxes and nowhere else*. And if I wanted to thicken that bit, there were even a couple of spare rolls up there ready.

Ah well.

Andy

[Hugo Nebula]

On Mon, 26 Nov 2007 07:38:08 GMT, a particular chimpanzee, Lobster randomly hit the keyboard and produced:

I wouldn't press him on it if I were you. Yes, you should have had a cavity tray, but it's one of those things that a blind eye is turned towards.

[Lobster]

Ah... too late actually: I got hold of him last night! He didn't mind talking (also I think the property/project had interested him as he'd been brought up in an identical house two or three doors away!) and he said that it's not something he would have insisted upon; yes, in an ideal world there should be one but it wouldn't be a compulsory thing for an old property. 'Surveyor covering his arse' was the phrase he used IIRC...

I didn't push on the issue of the 'change of use' of the roof which now encloses an internal space rather than an external wall, which is what I read about the other day as being the requirement for the cavity tray - is that where you're coming from?

Anyway - have asked the estate agent to tell the buyer to take a hike over it (in the nicest possible way) so we'll see what transpires.

David