Post and beam

I totally agree. No argument there. Which... is why i am trying to visualise a regime that gives me exactly that. My 1st floor ceiling ( airtight boundary) is as follows and from higher to lower 400mm rockwool 22mm caberboard decking 100mm rafters Intello airtight membrane Ceiling plasterboard Regardless of whether i go with my plan of boxed in light/ MVHR fittings within the 100mm rafter space being fed from above, below or horizontally i need to preserve the membrane as well as i can. i will provide a drawing tomorrow to better show the idea.

That sounds like it makes keeping the integrity of the airtight membrane even more complicated.

My understanding is that the roof membrane actually forms the watertight barrier from Rainfall. And that the tiles are there to protect the membrane. Am i wrong please? I have a little potential issue with the membrane and battening on the roof that the roofers are half way through. They have now broken up until the new year but i have a couple of small areas where rain has got in. Dormer valley for one of them and near to the gable ladder area for the other. I would rather my mind was put at rest and this be addressed before they crack on in the new year. Thanks in advance keith

Thanks for the responses yesterday guys, i feel more comfortable about this now. I intend to use the Pro Clima Intello Intelligent Airtightness Membrane at the ceiling ( warm side) Yes it is a pitched roof. I think there is a lot of work in making this Airtight boundary as good as it needs to be and still have access for the lights etc from the loft space cabling down through the membrane. Whilst also trying to make sure the plasterboard installers dont abuse my efforts.

Yep that was my question from the other day. I have a lack of understanding of the role of the ceiling membrane in my cold roof .

Our build is a 'cold roof' according to the TF provider. The airtight boundary is at the first floor ceiling level between the plasterboard and the rafters ( not yet installed). With 400mm rockwool due to be placed on the loft decking. So the loft will be unheated, and presumably cold in the winter because the insulation should make this so. My confusion is therefore..... If the airtight membrane allows vapour to pass upwards into the loft will it not condense out any moisture contained within ? Have i totally misunderstood the role of the various membranes? Highly likely i think.

Where in North Herts are you? We will be installing an Arotherm 7kw Once we get to that stage. Currently empty shell with roof tiles 50% done. Edit: Location added. We are in Aston, which is next to Stevenage.

Having just watched this video, apologies , i tried to just insert a link. At minute 2:15 i now believe i was correct and i do in fact have a warm roof design. This is getting confusing .

My effort to diagram what i have. I have seen descriptions of 'warm roof' that look closer to this than a cold roof design. Notice there is no insulation between the rafters here. Its all above, laid on the deck.

The beams will be on show yes. Yes of course the airtight layer needs to continue above the beams. There will be a plasterboard ceiling . The question is.... It appears that the TF design calls for a boundary at the point between the plasteboard ceiling and the horizontals of the roof trusses. (Rather than the upper limits of the roof) so is the usual practice to box around the light fittings?

Not sure if this is very clear, #1 shows the membrane above one of the beams. This is first floor ceiling. And #2 , the dark shadowy bit, Is the membrane above the studwork that makes up the first floor ceiling. So the perimeter of the first floor ceiling is a continuation of the airtight boundary from below. As stated previously, i could tape to, and continue this membrane across the whole first floor ceiling. No idea if this is the usual practice. But every light pendant would breach it and render useless. My TF frame company are very off hand now and just say ' this is for others'. Perhaps the usual thing is to box out the light pendant locations within the ceiling timbers, carry the membrane to these apertures leaving a smaller area to deal with after the lights are fitted. Any and all practical solutions or experience gratefully taken on board. keith

At a loss to understand how i can create the upper airtightness boundary.

I thought so.

No consistency at all, East herts did not want anything other than photos. In my submission for Bricks ,tiles and window colour i ended each sentence with ' or similar' . They did not comment or object which i feel gives me a degree of leeway should i need to change anything.

Hi Nick Described as a cold roof when i explained that the MVHR unit was going into the loft. 400mm of Ursa rockwool in the loft.