insulating log cabin workshop roof

[Setch]

I'm planning to build a log cabin garage to use a workshop in my garden. The supplier suggests insulating the roof with 50 mm foil backed insulating board, topped with roofing shingles. I plan to source the insulating board at a local supplier rather than pay the inflated price from the cabin supplier, but I'm unsure how to fix the insulation to the roof, or the shingles to the insulation. I'm also not sure whether with low pitched roof I need a membrane under my shingles, and if so where it should be - directly below the insulation on directly below the shingles?

Any suggestions from experience d parties would be gratefully received!

 

[MMUK]

I'd build it as a normal roof, something like this.

Assuming your roof joists are 3" x 2" or greater.

 

[Phil Pascoe]

Might be worth a look at secondsandco.co.uk for deals on insulation - they seem to have some good ones.

 

[MMUK]

BTW, build the roof as normal first. Insulate after from inside.

If your joists are only 2" deep, cut the Kingspan snug and then line the ceiling with plasterboard/hardboard/whatever.

If you are looking for a cheaper alternative, try just using flame retardant polystyrene sheets. I used that in my roof and it's about 1/4 the cost of Kingspan and does just as good a job.

 

[MickCheese]

I work from a log cabin. Before I used it my wife used it for her work.

I insulated it from the inside using 50mm kingspan boarded over with shiplap.

I thought a lot easier then doing it from the outside.

Mick

 

[Setch]

I can see the logic of insulating inside, however the roof is 19mm t&g, so it would be a shame to cover it, and I'm also reluctant to lose the headroom , as it is a low cabin to comply with building regs. The supplier (Dunster House) sell an insulation 'kit' which consists of 50 mm backed board bonded to mfp board, which is fitted above the t&g, then shingled over. However, having done some googling I've discovered I can source 50mm kinspan nearby for a about £250, compared to £690 for the suppliers kit. That seems like a Hu uuuuge saving, unless I've missed something?