Flat roof fail

[sxturbo]

One thing to check is what the architects plans advise. If the builder has built to plans, then he might have a get out of free cars and it will be the architects you need to go after.

When detailing parapets, the roofing material should go over the parapet under the coping stones. The coping stones should also be secured in place with rods to stop them moving and becoming loose. It's not just about installing a cavity tray.

 

[D0GMAN]

I wondered that too, we're currently trying to get in touch with the architect to clarify a few things.

This is from the architects specification document and blueprint.

IMG_0695

• D0GMAN
• 8 Nov 2021

IMG_0696

• D0GMAN
• 8 Nov 2021

This is from the builders original quote.

IMG_0694

• D0GMAN
• 8 Nov 2021

 

[sxturbo]

that does seem very much to be a build issue then based on the supplied information.

looks like the roof will need to come off, along with the coping stones and maybe mushroom vents installed, the roofing material to be taken up and over the inner leaf under the coping stones, and the coping stones ideally should be held in place with studs.

the roofing material neds to go over the inner leaf as per the attached crude drawing (roofing material in red) this is incase any of the joints between the coping stones fail and this stops the water from flowing behind the roofing material.

 

[D0GMAN]

that does seem very much to be a build issue then based on the supplied information.
looks like the roof will need to come off, along with the coping stones and maybe mushroom vents installed, the roofing material to be taken up and over the inner leaf under the coping stones, and the coping stones ideally should be held in place with studs.
the roofing material neds to go over the inner leaf as per the attached crude drawing (roofing material in red) this is incase any of the joints between the coping stones fail and this stops the water from flowing behind the roofing material.

Yes, I'm sure you're right. Mushroom venting looks likely from what I've seen if it has to remain a cold roof. The original rubber membrane did go up and over the parapet prior to coping stones being fitted. When they ripped out the rubber they cut it at the base of the roof so that rubber under the coping stones is still there.

20160608_151547

• D0GMAN
• 8 Nov 2021

 

[sxturbo]

Looks like it was done right first time apart from the venting.

2nd time it's been done wrong and still not vented

 

[Notch7]

With a parapet roof, I can’t see how the roof could be adequately ventilated.

looking at the construction images, my suspicion is the 120mm insulation may have been pushed up tight to the underside of the counter firrings…..leaving no cross ventilation.


I can see how it’s happened, I’ve been on sites where very similar has been done - I’ve had strong disagreements with builders on this - I did one orangery where the client engaged their own team to do the roof etc - and they insisted on putting the firrings above the insulation like you have.

 

[D0GMAN]

With a parapet roof, I can’t see how the roof could be adequately ventilated.
looking at the construction images, my suspicion is the 120mm insulation may have been pushed up tight to the underside of the counter firrings…..leaving no cross ventilation.
I can see how it’s happened, I’ve been on sites where very similar has been done - I’ve had strong disagreements with builders on this - I did one orangery where the client engaged their own team to do the roof etc - and they insisted on putting the firrings above the insulation like you have.

Doing a little research it doesn't seem to be that uncommon to get this wrong. Which begs the question, why isn't it being picked up by building control during construction, is it not something they routinely inspect? Probably being naïve here but aren't they at all responsible for passing off work that contravenes there own regulations?

 

[sxturbo]

Doing a little research it doesn't seem to be that uncommon to get this wrong. Which begs the question, why isn't it being picked up by building control during construction, is it not something they routinely inspect? Probably being naïve here but aren't they at all responsible for passing off work that contravenes there own regulations?

Lol, building control, full of People who haven't got a clue and ride the gravy train. They pick fights with things they don't need to and things they need to they ignore.

It's even worse when builders use their own inspectors, they just pass everything..

Best bit is they hold zero accountability.. imo they're a waste of time, but you have to use them.

See below where council inspectors have zero accountability.
https://www.stephens-scown.co.uk/co...ng-control-arent-liable-for-spotting-defects/

 

[datarebal]

It's even worse when builders use their own inspectors, they just pass everything..

Brave statement

 

[sxturbo]

Brave statement

They have zero accountability,

Least with the council ones they can be jobsworths, and suffer little man.tyoe syndrome.

Private inspectors have zero accountability also and are given the same rights as council engaged inspectors, so they really don't. Need to give a monkey's. The builders there mate, regular contract work so doesn't want to upset them incase it affects future work.

Building control really is pointless,

Another interesting legal read

https://www.fenwickelliott.com/research-insight/annual-review/2019/liability-approved-inspectors

 

[Notch7]

Doing a little research it doesn't seem to be that uncommon to get this wrong. Which begs the question, why isn't it being picked up by building control during construction, is it not something they routinely inspect? Probably being naïve here but aren't they at all responsible for passing off work that contravenes there own regulations?

It’s because building control is underfunded and inspectors are spread too thin.

I used to deal with a private building control and one inspector said he had 300 live jobs….no wonder they only spend 5 mins on site.

interstitial condensation is a complex problem and the nature of construction is the detailing can easily go wrong.

There have been major problems with new build houses - from the major housebuilders as a result of terrible interstitial condensation issues in walls and roofs.


And don’t forget our climate, flat roofs can get totally soaked by rain during construction

 

[D0GMAN]

All very illuminating and really shouldn't be a surprise. Think I might apply as a building reg officer, I'm sure I can manage to tick off a few boxes.

One more pic when they came out to replace the deck and rubber, showing the celotex up tight to the firrings as @Notch7 stated.

IMG_0338

• D0GMAN
• 9 Nov 2021

 

[sxturbo]

It very seems that you had 1 problem, and the builder trying to fix it without understanding the reason for failure , then failed to rectify the initial failure and introduced another fault.

Now you've found yourself with 2 faults.

The 2nd fault is easily fixed the roof needs to be installed as originally planned by removing the coping stones.

The roof, I.dont think can be turned into a warm roof without some major work, there isn't enough height on the parapet, so would need at least another course on the parapet, not sure if anything can be done in regard to the firrings to give you some additional room.

You could move the insulation down and install mushroom vents, not sure how many vents you'll need but I presume the roof will be peppered with them to get the air flow...

I think now the failures have been found and the cause, you now need fixes so you can get quotes and build up your case.

 

[D0GMAN]

@sxturbo Yes that all sounds right. To be honest it's already a bit of an eye sore, we used to have a nice view of the garden before, the extension mostly covers everything now, but of course that's on us. Loads of mushroom vents probably wouldn't improve the view unfortunately.
Pre action legal letter went out today so lets see what happens next.

 

[catlad]

Its a cockup in a few ways! but if you remove the parapet wall things will be a lot simpler.