revelation

We are looking to have a similar set up to yours. Our extract in the kitchen will be close to the hob but no directly over it. The extract point in the kitchen will have a grease filter set up to prevent any grease from getting into the system. We are also have a Bora re-circ hob fitted too.

We are going to have decking on-top so if we had felt it would be shaded from the Sun/UV. That should stop the felt from heating up significantly?

Would that be general Firestone or a higher grade? The contractor who suggested the Sika said he's done it before and on wood it will need a reinforcement mesh laid. Its literally twice the cost of GRP, he said it achieves the same performance as fibre but can be laid with less worry about the weather. Ideally I don't want to be paying twice the amount if I can have another material that will give me a suitable finish.

Thats the problem, the guys don't really want to do fibre because of the weather and its going to be difficult to get 3 days of good weather to ensure the right conditions for GRP. So I am going to have to go for felt, or on person has recommended going for Sikalastic 650, do you have any knowledge or experience with it? Regards

Right now the membrane is down (we have ordered more insulation for the warm deck). I assume its going to take that time due to all the insulation and OSB cutting, the detailing for the gullys and around the roof windows etc and the drains its all being bonded down too. I would have thought 2 days is enough but they have suggested 3 days to be certain.

Hi all, We have a bit of an issue, I have called about 5 different people to do do the GRP roof and they all all not keen to do it due to the weather. They said they would require 3 days of good weather to do this and its unlikely that we will have that any time soon. What would be the next best thing to use? Regards

I have previously spoken to the manufacturer about the slope of the walk on and they said it can be laid without a slope if we wanted due to the strength of the glass we wouldn't get pooling. But we are putting 1 degree on it. Its a good call speaking to the manufacturer about the 150mm to see if that can ben dropped due to the decking. Forming gullys around the roof light maybe possible but will be a pain as the roof light is in the middle and it will mean having to make further gullys off that to run to the edges. (I will speak to the builders about this one. My building control officer is fine with spray foam as long as the product is certified etc...

I don't think I am. I have attached the drawing of the glass on-top of the curb, from the finished GRP to the top of the glass its 190mm (according to the manufacturers instructions). So 190mm + 50mm (insulation) + 10mm (approx for GRP)+ 18mm OSB = 268mm 268mm is pretty much level with the sill. We could make the curb a little shorter so the side of the roof light frame is sitting close to the GRP but that still wouldn't give us enough room to get enough insulation on top. Thats why I have been exploring options to insulate below. I hope that makes clearer sense now.

Peter, we have gone through all the measurements and maths on this. We are restricted more than anything by the glass and its own frame around it, that has to sit around 80mm above the final roof finish. So an increase in insulation means a raising of the glass. The original plan of 50mm insulation was leaving us with the glass and decking all running flush (almost level with the door sill). Ideal Scenario is to be able to used closed cell spray foam underneath, what are your thoughts on this? Next best thing, we have a small step up next to the doors and the rest of the decking sits higher but flush with the glass. That will allow us to have around 120mm of insulation (We will probably still need more below?)

I think our choices are effectively either the spray foam if I feel reassured by people that it won't cause any condensation issues. Or to have a small step up next to the door ways and the rest of the decking to be higher but flush to the glass. If we did this the max insulation we could get is 120mm, so we would still need to put some below I assume to get to building regs?

So if I have the amount of insulation I said in the original post and spray foam insulation underneath will that work as far as building regs go and no issues with condensation?

Maybe a silly question, but are their different grades of fibre? What should I be looking out for or questions to ask to a installer?

Thats really interesting, someone else had advised that closed cell spray foam may work on the bottom as it will expand and fill in any gaps therefore there isn't anywhere for condensation to form. I have mentioned it as an option but so far no one else that has replied has said its a good idea or will definitely work.

The step is approximately 250mm, I don't know the exact height of the upstand and the glazing, but where the glazing finishes is level with where the step comes (so approximately 250mm). The glazing has attached frame which comes over the upstand so as the insulation increases so does the starting point of the upstand. I have attached some images if the roof light on a previous post.

Unfortunately all the joists have been set in place and bricked in, we also have set of large sliding doors in the kitchen below which are effectively floor to ceiling (approx 2500mm) so even if we wanted to lower inside we couldn't really do that.