Summer house insulation ceiling or roof

Bendy_House

Your roof looks as tho' it could do with some tie-beams? It's a bit saggy in places?

How important is having the full vaulted internal ceiling to you? If 'not', or if you'd be ok with partial-vaulted - eg ~1' of sloping eaves and a flat ceiling above this - then I think this is what I'd do as it should be very effective, be simple and cheap to carry out, not risk any damp or trapped condensation issues to the roof, and also not require any of the existing structure or roof covering to be dismantled.

First, decide whether some tie-beams are required in order to pull the shed sides together. If they are needed, then great - you'll also be using them for your new ceiling  

Fit these at whatever height suits you best - would ~1 foot up from the eaves be ok? The roof space ABOVE this will now be ventilated thoroughly in order to prevent any damp issues. The simplest way, I think, would be to drill 2 or three round holes in each 'gable' and fit meshed vents like wot they fit to soffits. That will allow a through-draught up there and keep things nicely dry.

NB: the whole void above this new ceiling will need to be ventilated. See the purlins running longways along the roof? What are they - 2"? 3"? Your new ceiling will be fitted to this to leave that gap above it, and it's important that ALL the voids are ventilated. So make sure that ALL these voids have a vent fitted either end. Does that make sense?

Now line the sloping eaves using 1 or two inch rigid, foiled-covered, insulation board like Celotex. Bevel/mitre the ends to fit neatly against the shed walls, and against the horizontal sheet that'll form your new ceiling. Before fixing, run a bead of exp foam along each joint to fill them, and also against where the sheets meet the shed walls. Ideally, foil-tape all the joints too.

Now cover the insulation with the ceiling surface finish of choice; this could be lightweight T&G timber cladding (if you miss the wooden roof), lightweight T&G PVC ditto, plasterboard, or - at its simplest - even thick lining paper to be painted afterwards.

(You did remember to mark out where all the rafters and tie-beams were, didn't you?)

Your ceiling will now be highly insulated, and the roof void above safe and sound.

How thick the rigid insulation? Even a single inch of Celotex/Kingspan type stuff will be simply transformative, so even this will be hugely worth-while, and will also be 'enough' if you don't want to lose too much headroom. 2" will, of course, be even better, but nowhere near 'twice' as good.  

If you line the underside with T&G cladding, either timber or PVC, this again will add useful insulation.

DRP

How is it heated in the winter? 

kowalski181

Thanks for the advice, a lot to weigh up. I get by fine in the winter, lots of condensation sometimes but going to get some film for the windows. I have a decent panel heater and I get by fine when working in there. The roof does look a bit sunken on that picture you are right. I think I am going to go for indoor option as that will end up being easiest. Thanks again 

kowalski181

Bendy_House said:

Your roof looks as tho' it could do with some tie-beams? It's a bit saggy in places?

How important is having the full vaulted internal ceiling to you? If 'not', or if you'd be ok with partial-vaulted - eg ~1' of sloping eaves and a flat ceiling above this - then I think this is what I'd do as it should be very effective, be simple and cheap to carry out, not risk any damp or trapped condensation issues to the roof, and also not require any of the existing structure or roof covering to be dismantled.

First, decide whether some tie-beams are required in order to pull the shed sides together. If they are needed, then great - you'll also be using them for your new ceiling  

Fit these at whatever height suits you best - would ~1 foot up from the eaves be ok? The roof space ABOVE this will now be ventilated thoroughly in order to prevent any damp issues. The simplest way, I think, would be to drill 2 or three round holes in each 'gable' and fit meshed vents like wot they fit to soffits. That will allow a through-draught up there and keep things nicely dry.

NB: the whole void above this new ceiling will need to be ventilated. See the purlins running longways along the roof? What are they - 2"? 3"? Your new ceiling will be fitted to this to leave that gap above it, and it's important that ALL the voids are ventilated. So make sure that ALL these voids have a vent fitted either end. Does that make sense?

Now line the sloping eaves using 1 or two inch rigid, foiled-covered, insulation board like Celotex. Bevel/mitre the ends to fit neatly against the shed walls, and against the horizontal sheet that'll form your new ceiling. Before fixing, run a bead of exp foam along each joint to fill them, and also against where the sheets meet the shed walls. Ideally, foil-tape all the joints too.

Now cover the insulation with the ceiling surface finish of choice; this could be lightweight T&G timber cladding (if you miss the wooden roof), lightweight T&G PVC ditto, plasterboard, or - at its simplest - even thick lining paper to be painted afterwards.

(You did remember to mark out where all the rafters and tie-beams were, didn't you?)

Your ceiling will now be highly insulated, and the roof void above safe and sound.

How thick the rigid insulation? Even a single inch of Celotex/Kingspan type stuff will be simply transformative, so even this will be hugely worth-while, and will also be 'enough' if you don't want to lose too much headroom. 2" will, of course, be even better, but nowhere near 'twice' as good.  

If you line the underside with T&G cladding, either timber or PVC, this again will add useful insulation.

This seems like an excellent idea and thanks for the detailed explanation but it is way above my level of DIY competency, I have no idea what a tie beam is I'm afraid. I think I will just get some batterns create the air gap, pop the ,25 or 50 ins boards in then have another small gap and t and g lengthways down to the other side over the supports that are already there

Bendy_House

A tie-beam is just the horizontal bar of an A-frame. It ties the /\ together, and prevents them from doing the splits and pushing out the sides of your shed.

A few 3x2 - or even 2x1 might do - screwed through the existing rafters on your roof to 'tie' them together, once you've pulled the shed sides together.

If you measure the internal width of the 'shed', at top-of-wall height, in a number of places, it should be obvious if the shed walls are bulging out under the weight of the roof in the middle of the wall - ie if the mid-widths are greater than at the end walls.

If your shed walls are bulging out, then - really - this needs doing.

And, if it needs doing, then it can be made to also form ceiling rafters.

stuart45

Has your roof got any rafters? It looks like purlins and a ridge beam.

Bendy_House

stuart45 said:

Has your roof got any rafters? It looks like purlins and a ridge beam.

Eek! I saw that wrong - these are just noggins! 

(In which case, scrap everything I said before... )

kowalski181

Yeah not the best summer house in town haha but it does the job. Will.proceed with the ins boards inside and tongue and groove over with some additional battens to adjoin to. Thanks again 

Bendy_House

Please make sure that the void above the insulation is ventilated. It probably will be to some extent anyway just due to air leakage past joints and other gaps, but you don't want that sealed-off gap above the insulation to be sweaty.