fixing methods for celotex warm roof insulation

[mpheating]

i see the foil backed plasterboard mate, ill grab myself some of that for what its worth.

just one more quick question, ive been offered some celotex 150mm insulation at a decent price, if i laid this on the joists and then put 18mm swb board directly on top, mechanically fixing through the both into the joists with Helical nails...would this be ok?

quick re-cap because i think this will be my finished plan lol

1. get joists cut pre angled from wood yard
2. lay insulation directly on top of joists, taping all joints with silver foil tape
3. lay 18mm swb board on top of insulation and fix using helical nails through board, through insulation directly into joists.
4. fit rubber roof
5. seal all insulation joints internally
6. board roof with foil backed plasterboard
7. plaster
8. get back to some plumbing work

sorry to be a pain in the arse you have been a great help

 

[noseall]

Sounds like you have it weighed up to me.

Just remember to put the joists the right way up!

And it's gonna be one heck of a deep fascia to cover all that thickness of roof material.

 

[mpheating]

yeah i no about the fascia board lol not the best...

whats joists...150mm x 50mm every 400mm centers

plus 18mm board and 150mm insulation..

320mm board

haha it is a decent size but i would rather put decent insulation in now than regret it later as it will be heated with a wall fan convector heater

 

[noseall]

You are on the limit with span (3m) for 6" x 2" timber so these won't tolerate the trimming down for the slope of the roof. You would be wiser to add firring strips rather than cut the joist.

 

[seasickstevie]

Why not just give the joists 'fall'?

 

[noseall]

Why not just give the joists 'fall'?

What, then level them out with firring strips before tacking the ceiling and faff about trimming all those joist ends back to upright?

Or are you suggesting having an out of level ceiling whereby your datum is lost, all wall plasterboards would need cutting on the slopes, coving would be a mare, blah blah.

ALWAYS FIT STUFF LEVEL.

 

[catlad]

Its a garden shed.

 

[noseall]

Its a garden shed.

and.....?
Is that a reason to employ amateurish and regrettable building practices?
Tacking a firing strip is far easier than alternatives leaving you with a manageable building rather than an afterthought headache.

 

[catlad]

I am sure he is an amateur thats why he is on a diy forum asking for advice and I am sure its easier to nail a piece of 4x2" to one side of the wall plate to his building to create a slope rather than go to somewhere and order timber firrings.

 

[seasickstevie]

... coving would be a mare, blah blah.

Garden shed with covings

 

[noseall]

I am sure he is an amateur thats why he is on a diy forum asking for advice and I am sure its easier to nail a piece of 4x2" to one side of the wall plate to his building to create a slope rather than go to somewhere and order timber firrings.

Yes and the have fun countering that slope with all the other things throughout the build.
Very shortsighted.

 

[mpheating]

I am an amateur when it comes to building as it's not my trade but saying that my standard of work is excellent and i don't like cutting corners, I will see which way is cheaper from the wood yard, larger joists cut down or fittings, at the end of the day it's not a huge problem but thanks for trying to help

 

[noseall]

I am an amateur when it comes to building as it's not my trade but saying that my standard of work is excellent and i don't like cutting corners, I will see which way is cheaper from the wood yard, larger joists cut down or fittings, at the end of the day it's not a huge problem but thanks for trying to help

Trust me, in spite of what the bodgers are saying you do not want a sloping ceiling or a canted fascia.

 

[cotswoldbuilders]

Same as Noseall said, proper and easiest way is fit level timbers with firrings on top.

 

[mpheating]

yer i will definitely fit level with firrings as suggested, thanks again