Insulating Summer House Roof

Sirrel Squirrel · 19 Sep 2023 at 12:38

Anyone ever insulated a summer house roof? I've got a wooden summer house in the garden and would like to put in insulation (Celotex) below the roof and then plaster board. Question I have is does the cabling for the lights go above or below the insulation material? I'm getting conflicting information and can't work it out lol.

So should it be Insulation > Cables > Plaster Board or Cables > Insulation > Plaster Board?

200sols · 19 Sep 2023 at 12:57

Clip cables to a joist, insulation between joists.

Sirrel Squirrel · 19 Sep 2023 at 13:07

Thank you that does make perfect sense

Lean · 19 Sep 2023 at 13:21

If height isn't an issue you can batten the rafters for more depth of insulation. Then if you wanted you could use insulated plasterboards as well. Don't forget a vapour barrier.
I forgot is it a cold or a warm roof system you are going for?

Sirrel Squirrel · 19 Sep 2023 at 13:33

The joists are pretty high at 190mm, so I was going to put in air soffits where the void will be, then have 100mm Celotex that'll be flush with the bottom of the joist and then plaster board. The intention is to keep in heat in the winter although in the summer it has been very hot in there.

eggbert · 19 Sep 2023 at 21:53

I put the insulation on the outside between the roof and the felt shingle's but if your roof is already on it makes sense to do inside. I did outside to help with any condensation issues and used a guide here https://www.tuin.co.uk/blog/roofing/log-cabin-insulation-floor-and-roof/

ANDARIAL · 20 Sep 2023 at 09:05

I would use ply instead of plasterboard personally,have you thought about the `damp/condensation`in the winter months?

Sirrel Squirrel · 20 Sep 2023 at 12:15

ANDARIAL said:
I would use ply instead of plasterboard personally,have you thought about the `damp/condensation`in the winter months?

Based on what the guy putting in the insulation said, he's going to put air vents/soffits between each of the joists so each part of the void/air gap will be vented so I assume that'll be fine?

ANDARIAL · 20 Sep 2023 at 13:19

I was thinking more of mould and damp on the inside of the roof.i.e. inside the building

rangor gubbins · 23 Sep 2023 at 20:20

ANDARIAL said:
I was thinking more of mould and damp on the inside of the roof.i.e. inside the building

I'd agree. If there's no heating running through the winter I think it could get damp inside even with the insulation, and the plaster could get mouldy. Ply is more resilient especially if sealed/treated.

Sirrel Squirrel · 25 Sep 2023 at 12:16

Thanks for the tips on damp, I'm going to have a heater in there over winter, would I also need a de-humidifier?