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Conversions

insulate all of roof or just from purling to ridge?

Anonymous user 16/03/2024 - 2.39 PM

Hi, we are converting the loft into a bedroom and need to make the rafters bigger to accomodate the kingspan. We then have to fit insulated plasterboard to the underside of this. My architect/designer has unfortunately had to take time off work and is currently not answering emails. We will be building stud walls directly below the purlings an each side. My first question is - should I fill the gaps between the rafters below the purling with kingspan too? (as in behind the walls in the eaves) and does this need insulated plasterboard? My second question is, once I have installed the kingspan between rafters should I build the stud wall for the ensuite before installing the insulated plasterboard each side of it or should I install the insulated plasterboard and then build my wall underneath that? Finally, If I do need to insulate between the rafters below the purling do I also need to insulate the stud wall going under the purling? thank you

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3 Answers

Anonymous user

Your better off insulating the whole roof in between the rafters and in the floor area

Answered30 January 2021

Anonymous user

Hi how’s you Ok if your studs are made or if you make the studs that split the room from The void , If your standing in the room now you should have rafters and two studs with the voids behind them . You put the 100mm kingspan from the point off the roof rite down the rafters till you reach the back of the stud wall , then but the 100mm kingspan into the stud wall keeping it flush with the room side of the stud , the kingspan should also be flush with the bottom of the rafters or room side , after this is done you should have a air gap up the back of the insulation between the insulation and the roof itself , there should be no kingspan in the void , your insulation plasterboard goes over all your kingspan rafters and stud , In the voids you use earth wool insulation in the floor only breathable it should be , it does not go between roof rafters , if your floor is not down yet this is what goes between your floor joists to , if the floor is down tuck it well below the floor from The void and tight round the wall plate at the outside , I would say you should make all your studs in the room before you put insulation in this way the studs can be fixed tight at the top to the rafters and it will help to stop the plaster cracking . The air gap round behind the kingspan is very important, it’s also important you don’t leave any gaps in the kingspan , any parts where you are cutting again twisted timbers or round chimneys or along walls if there is gaps you should run round the edges with expanding foam to fill them out and keep the kingspan tight . Depending on the shape of your room I find it sometimes cheaper to use 50mm kingspan across the rafters then fix 12.5mm plaster board over it rather than have lots of waste cutting insulation plasterboard time meet rafters and studs Hope this helps Many thanks Paul

Answered1 February 2021

Patrick Thompson

Rating: 5 out of 5

Orpington

The last answer was good but I would also insulate all of the stud work as well. Don’t use plasterboard in the en suit but there is a better water proofing board on the market that is suitable for interior bath and shower rooms. Make sure all regulations are up to date with the council and masked sure your insurance company is informed of your works. Good luck

Answered24 February 2021