warm roof vapour barrier

[freddiefox]

Realised yesterday we've ommitted to take care of adding a vapour barrier in our new flat warm roof construction. Its not yet built but will be in the next few days so I'm under pressure!

Our original plan was to use 120mm ecotherm and tape the joints but this doesn't look sufficient.

Can anyone recommend a product/brand that fits the bill, doesn't cost the earth, self healing (as someone recommended to me) and up to current building regs?

Any other considerations greatfully received!

TIA!

 

[freddiefox]

Anyone?

Any views on this product for a warm roof? http://www.roofingsuperstore.co.uk/...t-of-42.html?gclid=CNDM-Kf7o8ACFSoEwwodkg8Auw

I've tried to get some of this as recommended by someone - cant find it anywhere - Sig dont have any locally either

http://www.siginsulation.co.uk/show_prod.asp?ProdID=1881&CatID=36&SubCatID=74

 

[freddiemercurystwin]

A vapour barrier when used for this type of application is just a thin plastic sheet eg http://www.ebay.co.uk/itm/2-5m-Wide...t=LH_DefaultDomain_3&var=&hash=item3a8be91b98

Forget felt or some fancy pants aluminium fella!

 

[freddiefox]

hello fellow freddy!

see thats what i thought too, however im getting different advice. We haven't yet confirmed roof covering - still waiting on a sample & quote. It appears I've been advised the type you suggest or vis queen by someone fitting rubber, or I've been advised a biutmen self healing type by someone fitting Zinc. Do you know if the final roof covering impacts what the vapour barrier should be?

It makes me think the zinc is likely to fail - wrongly or rightly

 

[freddiemercurystwin]

The purpose of the vapour immediately underneath the insulation is to minimise any moisture from entering the insulation whereupon it could condense against the underside of the roof covering, saturating the insulation. The choice of vapour barrier has nothing to do with the roof finish.

Different roofers will have different preferences, but really they all do the same thing. Some will use this manufacturer or that or from that supplier or that, using one that won't tear so easily or using a 1m wide roll on a windy day may be valid considerations for instance.

The purpose of a 'self healing' one is that its supposed to self heal if its damaged during construction (ie by a builder dropping a hammer on it or scuffing it with his size 12 boots or if it is penetrated with any screws or whatever. Again nothing to do with the choice of roof finish. But really its a bit of a gimmick.

 

[freddiefox]

Thank you!

So if we use just a plastic sheet type vapour barrier, how do we fix it without piercing it and compromising it? or do we just screw through? We are using staifix super 8's. I've been told the reason for the bitumen based one is because its self healing when you screw through. I just finally had a quote on the Alutrix 360 quid! just wow....

A completely separate question, but I'd really appreciate some help. I believe we need a 150mm upstand on a parapet wall/flat roof. We've around a 3 degree fall from the centre to the left and right. I've just measured and we're maybe 70mm odd short on a very small area of the front of the roof where the highest part is. Its around 1m length of 7m impacted. Are BC usually bothered on this (its a refurb not a new build, though warm roof means completely new roof build anyhow)? Is there another way around it without having to build up another row of bricks all the way around? I assume that 150mm does not include copping stones either.

 

[freddiemercurystwin]

You often pierce a vapour barrier, it could be the foil on the back of plasterboard or like this, whereby the fixings may penetrate the VB directly. There's not much you can do about but really its not much or a problem, there will theoretically be some leakage but really you're thinking too much. Had this been a swimming pool roof for instance I would be concerned, in a dwelling don't worry about it.

The 150mm is height of the flashing up to the underside of the coping. BC may allow 70mm as its a refurb. It will be slightly increased risk of course though.

 

[freddiefox]

Brilliant - thank you! Will check-in with BC