House built in 2016 - No loft insulation?
Discussion
No Redrow plot I’ve been on has had a warm roof on a 2 1/2 storey plot, but that’s not saying it exists.
Hard to judge but from the pic it looks like 2 sheets of plasterboard on the underside of the ceiling rafters so around 2.4m to the gable, no trusses so I’m guessing your roof is a cassette built roof, panels dropped on with crane rather than a cut roof or top hats which is usually the case on attic trusses if the height is more than a hgv can carry to site.
OSB board is for bracing on attic truss roofs, you could drill a hole with a hole saw somewhere in it to determine celotex behind but to get a CML it surely would have been checked at pre plaster stage for insulation.
If it has celotex behind the OSB above ceiling rafters there is no need to insulate your rafters, you could if you wanted too though.
In the 2 voids either side lower down you’ll have insulation on the first floor ceiling level but also you might have it in the top floor uprights, it depends as we used to insulate from wall plate up on the rafter pitch but regs do get altered.
If that gable is a party wall with a neighbour chances are that’s a spandrel panel, ie a timber truss with double layer plasterboards on either side.
Hard to judge but from the pic it looks like 2 sheets of plasterboard on the underside of the ceiling rafters so around 2.4m to the gable, no trusses so I’m guessing your roof is a cassette built roof, panels dropped on with crane rather than a cut roof or top hats which is usually the case on attic trusses if the height is more than a hgv can carry to site.
OSB board is for bracing on attic truss roofs, you could drill a hole with a hole saw somewhere in it to determine celotex behind but to get a CML it surely would have been checked at pre plaster stage for insulation.
If it has celotex behind the OSB above ceiling rafters there is no need to insulate your rafters, you could if you wanted too though.
In the 2 voids either side lower down you’ll have insulation on the first floor ceiling level but also you might have it in the top floor uprights, it depends as we used to insulate from wall plate up on the rafter pitch but regs do get altered.
If that gable is a party wall with a neighbour chances are that’s a spandrel panel, ie a timber truss with double layer plasterboards on either side.
Edited by Promised Land on Thursday 6th February 11:32
Promised Land said:
No Redrow plot I’ve been on has had a warm roof on a 2 1/2 storey plot, but that’s not saying it exists.
you could drill a hole with a hole saw somewhere in it to determine celotex behind but to get a CML it surely would have been checked at pre plaster stage for insulation.
dont Redrow use their own pet BCO?, they probably didnt inspect it??you could drill a hole with a hole saw somewhere in it to determine celotex behind but to get a CML it surely would have been checked at pre plaster stage for insulation.
Edited by Promised Land on Thursday 6th February 11:32
Promised Land said:
No Redrow plot I’ve been on has had a warm roof on a 2 1/2 storey plot, but that’s not saying it exists.
Hard to judge but from the pic it looks like 2 sheets of plasterboard on the underside of the ceiling rafters so around 2.4m to the gable, no trusses so I’m guessing your roof is a cassette built roof, panels dropped on with crane rather than a cut roof or top hats which is usually the case on attic trusses if the height is more than a hgv can carry to site.
It certainly looks like a cassette built roof. Would be a standard plasterboard finish if it were any other warm roof construction.Hard to judge but from the pic it looks like 2 sheets of plasterboard on the underside of the ceiling rafters so around 2.4m to the gable, no trusses so I’m guessing your roof is a cassette built roof, panels dropped on with crane rather than a cut roof or top hats which is usually the case on attic trusses if the height is more than a hgv can carry to site.
Drive wrench, this is a cassette roof, which can be a warm roof if the cassette have insulation in them...
https://pasquill.co.uk/roof-solutions/roof-cassett...
https://pasquill.co.uk/roof-solutions/roof-cassett...
You are still stopping airflow there IMO. There might be an air gap but it wouldn’t flow freely
What I would do if height is at a premium is to fit 50/60mm square lengths of wood across the joists then lay the boards on top of that. It doesn’t take too much of height but raises the boards so there is a bit of flow underneath. I had to do similar in the centre section in my loft due to the extreme low pitch. I used the full loft legs at each end then the above method in the centre around the loft hatch.
EDIT: I would also leave a decent gap around the edge to also promote airflow
What I would do if height is at a premium is to fit 50/60mm square lengths of wood across the joists then lay the boards on top of that. It doesn’t take too much of height but raises the boards so there is a bit of flow underneath. I had to do similar in the centre section in my loft due to the extreme low pitch. I used the full loft legs at each end then the above method in the centre around the loft hatch.
EDIT: I would also leave a decent gap around the edge to also promote airflow
Edited by SteBrown91 on Thursday 6th February 19:36
DriveWrench said:
Righto guys - I think I'm going to err on the side of caution and just put some insulation down before putting the boards up. I don't have any heat loss issues in the room below (in fact, it's one of the warmest in the house), but for the sake of £100 or so, it's probably worth doing.
However, the height of the current floor joists are 170mm and I've read that 270mm is now the regulation height required on new builds. As I don't have any issues with heat loss as it is, would it introduce any problems with damp (etc) if I put 150mm of insulation down (leaving a 20mm gap for airflow) and putting loft boards directly on top of the joists? I'm keen to avoid adding any risers as the space in there is tight as it is, especially if it may not be required anyway.
There is also two areas on either side of the loft which wouldn't be boarded, so wondering if I can keep these as is. The sloped roof meets the floor and there is no gap (if that makes a difference).
Rather than send another poor photo (no ladder to get up there easily) I have done a semi-accurate model of what I'm thinking.
If you feel that way why not just use 100mm rockwool and 19mm boarding?However, the height of the current floor joists are 170mm and I've read that 270mm is now the regulation height required on new builds. As I don't have any issues with heat loss as it is, would it introduce any problems with damp (etc) if I put 150mm of insulation down (leaving a 20mm gap for airflow) and putting loft boards directly on top of the joists? I'm keen to avoid adding any risers as the space in there is tight as it is, especially if it may not be required anyway.
There is also two areas on either side of the loft which wouldn't be boarded, so wondering if I can keep these as is. The sloped roof meets the floor and there is no gap (if that makes a difference).
Rather than send another poor photo (no ladder to get up there easily) I have done a semi-accurate model of what I'm thinking.
As Wolfracesonic indicates, insulating at ceiling level will cause issues. If, as looks to be the case, it’s a warm roof the black material you can see through to around the OSB will be a plastic vapour barrier (Celotex and similar most frequently have a silver foil face). This stops water vapour entering the construction and condensing in the colder layers of the build-up (interstitial condensation).
By insulating the void at horizontal ceiling level you are making the void above a cold roof - a traditional loft space I suppose. Not a problem, but a cold roof must be ventilated to deal with the water vapour that will inevitably penetrate into the void. Arranging this would be a massive headache, but more importantly would render the insulation in the warm roof structure redundant - you would be inviting the outside air to come inside the warm roof structure.
I would board the void without any additional insulation and then everything remains within the warm roof envelope and untroubled by condensation worries.
By insulating the void at horizontal ceiling level you are making the void above a cold roof - a traditional loft space I suppose. Not a problem, but a cold roof must be ventilated to deal with the water vapour that will inevitably penetrate into the void. Arranging this would be a massive headache, but more importantly would render the insulation in the warm roof structure redundant - you would be inviting the outside air to come inside the warm roof structure.
I would board the void without any additional insulation and then everything remains within the warm roof envelope and untroubled by condensation worries.
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