roofers installed vented soffit - building regs no likey

davebwithane · Posted: Wed Feb 29, 2012 1:17 pm

Hello
Just had building regs round to look at my re-tiled, re-soffited and re-fascia'd roof.
The soffit and fascia has been installed and the soffit is vented. Building regs say this is incorrect and it should not have been vented.
Now what do I do ? Big job to get it removed. Is there something I can put over the vents ?
Thanks
Dave

freddymercurystwin · Posted: Wed Feb 29, 2012 1:52 pm

Can you explain a bit more about the roof construction, why BC are involved and why they have said the venting is incorrect. What underlay was used breathable or felt?

You saying they won't approve it with the vents insitu?

davebwithane · Posted: Wed Feb 29, 2012 2:09 pm

Thanks.

Had the roofed stripped, celutex put in between the rafters, breathable felt over then re-tiled.

They said the airflow is incorrect with vented soffits insitu and they need to be taken out before approval is given. No vents required at all due to breathable felt.

Regs involved 'cos the entire roof covering is being overhauled.

freddymercurystwin · Posted: Wed Feb 29, 2012 3:07 pm

You do mean rafters and not joists?

If so then the loft has been converted presumably? If so are you saying the Celotex runs all the way down the rafters to the eaves and effectively the ventilation is able to get beneath the Celotex? The Celotex needs to meet the wall insulation to make an 'insulation bubble' around the living area.

There are certain circumstances where additional venting above the insulation is required when using a breathable membrane but these can largely be designed out so we assume the roofers have made a booboo!

davebwithane · Posted: Wed Feb 29, 2012 3:30 pm

Thanks. Yes I meant rafters. The main reason for putting the celotex in between the rafters was because of draughts in the house and to make it more useable up there.

Just spoke to principal building regs guy - solution is to cover over soffit vents with plastic strip and not to ventilate the roof. The air pressure build up within the roof space will then be enough to send moist air through the breathable membrane. That's the theory anyway.

freddymercurystwin · Posted: Wed Feb 29, 2012 3:49 pm

Ahh OK hope you didn't pay for those vents then!

davebwithane · Posted: Wed Feb 29, 2012 3:54 pm

yes unfortunately I did

davebwithane · Posted: Wed Feb 29, 2012 6:46 pm

so does it sound right to you guys - no ventilation ? So the moisture is supposed to go through celotex and then the felt membrane only by the build up of pressure it creates up there itself and that's the only way it gets out ? doesn't sound right to me, but that's why I'm on here ..
thanks again.

noseall · Posted: Wed Feb 29, 2012 7:29 pm

davebwithane wrote:

. The air pressure build up within the roof space will then be enough to send moist air through the breathable membrane. That's the theory anyway.

Sounds like blarney to me.

davebwithane · Posted: Wed Feb 29, 2012 8:21 pm

just been reading the housebuilders bible (not that I am buiding a house). But the whole theory behind roof ventilation seems to be just that. There doesn't seem to be any hard and fast rules to stop condensation building up. I'm trying to workout if the warm roof space I now (or will have once soffit vents are sealed up) is going to cause condensation build up or not. Maybe the permeable membrane is enough for airflow, who knows ?

davebwithane · Posted: Wed Feb 29, 2012 8:52 pm

interesting ..

http://www.thenbs.com/topics/ConstructionProducts/articles/ventedUnventedRoofConstruction.asp

"The enclosed void of a warm pitched roof does not require to be ventilated"

http://www.planningportal.gov.uk/permission/commonprojects/roof/

"Not all roofs need to be ventilated. Ventilation is not required to a warm roof system, which is where the insulation is placed above the joists or rafters."

freddymercurystwin · Posted: Wed Feb 29, 2012 10:12 pm

noseall wrote:

davebwithane wrote:

. The air pressure build up within the roof space will then be enough to send moist air through the breathable membrane. That's the theory anyway.

Sounds like blarney to me.

No, effectively this a loft conversion in terms of the insulation bubble noseall. Either vent the gap or fit a breathable membrane (albeit following the strict fitting guidance as breathable membranes do sometimes need additional ventilation). That's the theory anyway.

Nige F · Posted: Thu Mar 01, 2012 9:09 am

davebwithane wrote:

t. Maybe the permeable membrane is enough for airflow, who knows ?

Not for me , it`s not : BUT I`m only an old school plumber with general building experience . I know what I would do - cover the vents until it`s all signed off - then ......

The devil is in the detail with roof insulation , you have to work out exactly where and how much the air is going to flow : FMT and Nose have that experience . At my last house ( chalet bungalow) an existing extension had all the work under Sussex ( Wealden ) BC signed off and I found the air from the continuous soffit vents was going under the floor of the bedroom/ ceiling of living room - instead of round the "bubble"

freddymercurystwin · Posted: Thu Mar 01, 2012 9:37 am

Nige F wrote:

davebwithane wrote:

t. Maybe the permeable membrane is enough for airflow, who knows ?

Not for me , it`s not : BUT I`m only an old school plumber with general building experience . I know what I would do - cover the vents until it`s all signed off - then ......

The devil is in the detail with roof insulation , you have to work out exactly where and how much the air is going to flow : FMT and Nose have that experience . At my last house ( chalet bungalow) an existing extension had all the work under Sussex ( Wealden ) BC signed off and I found the air from the continuous soffit vents was going under the floor of the bedroom/ ceiling of living room - instead of round the "bubble"

I'm guessing the vents allowed airflow directly into the loft otherwise I don't see why BC would have condemned them but who knows! As you say if the vents were allowing airflow into the gap between the ins and U/S of the tiles that'd only be a good thing.

paulandfrodo · Posted: Sat Mar 10, 2012 8:13 pm

I thought the construction was celotex between and OVER the roof joists. This would be up to the required amount to achieve app. U values.

You then have an air gap between the celotex and breathable membrane, then tiles. Can't remember if it's 25mm or 50mm gap - sorry, it sat. night and I've had wine !

You have a vented soffit and vented ridge (marley do various systems).

Thus moisture is taken up and out. Ensure you drill app holes through any noggins used with rafters - esp. where velux windows are.