To allow 50mm ventilation gap under the bitumen, non breathable membrane, we have drilled holes through the noggins, but right at the gable end, it's not really possible. It will be a kitchen wall, so moisture might be an issue. There will be insulated PB over the PIR between the rafters with a VCL.
Will it be ok to just seal this bit up and not worry, or should I think about some kind of breathable option for the wall (I'm thinking clay or lime plaster type stuff). (I know I'm mixing my modern airtight concepts with breathable buildings, but bare with me!)
Perhaps look at Saxon TCT blades. Not the best but cheap enough that you can buy more than one with different number of teeth. I'd look for something around 40 teeth. The overall diameter and the hole diameter need to match your saw.
Personally I'd use a table saw for this rather than a hand held circular saw. Its difficult or rather time consuming clamping narrow boards so they can be cut down the middle with a hand held. Not enough (any) board sticks out of the side so the saw can't go past the clamp. If you have a lot to do perhaps look on YouTube for ways to turn a hand held saw into a table saw?
Hi thanks again for quick replies as have been really worried since spotted it earlier just after builders left, the SE specified Catnic lintel REF CG110/100 for 125mm cavity min 200mm end bearing, the opening is 2500 for the bifolds, in terms of the blocks not really sure they are not high density or anything and just assume standard blocks if there is such a thing (very new to all of this). Has the builder swapped catnic for keystone based on few of the questions/comments ?
Guess thing that is really concerning me is does this need to be re-done or can bi-folds be fitted underneath okay - not yet ordered was waiting for all opening and then manufacturer was coming to measure, guess didn't want big thick sealant to take up any deformaties or do they normal have some sort of head where beam deflection can be catered for ?
Many thanks again, especially on a friday night.
This is exactly what I have found, 150mm x 22mm sarking boards with a 3-5mm gap are very permeable and the roof performs really well, but as soon as you use sheet board it’s impermeable and need fairly serious ventilation below to stop moisture build up - this then leads to mould….. don’t ask how I know 😥 I would personally always use 150mm x 22mm sarking board on any future roofs I build but I also put a 50mm ventilation gap below them as well !