Which insulation for fitting from below

[Beanwood]

As per post title really.
Rather than wait until it is already freezing I thought it time to insulate the workshop and put some heating in. It won’t be perfect as it’s solid breeze block and stone construction- but the roof is what really lets it down.
The gaps between rafters varies by an inch or four- it’s a sloping roof if that’s important- and I have not planned to plaster it after- so is the answer solid board of some type cut to shape with a handsaw?

 

[Blobber]

Plasterboard backed with celotex type stuff and run some timber battens down the joints? whatever you do leave an air gap between the insulation and felt, you also ought to unblock the bottom of the timbers so you get some airflow between the felt and insulation

 

[DaveB]

Plasterboard with mineral wool to fill most of the gap.
Less of a fire hazard than celotex.....

 

[Erie Fred]

Many shops around here are applying standard 29g roofing tin, you can blow
cellulose in afterwards.

 

[gaz1]

As per post title really.
Rather than wait until it is already freezing I thought it time to insulate the workshop and put some heating in. It won’t be perfect as it’s solid breeze block and stone construction- but the roof is what really lets it down.
The gaps between rafters varies by an inch or four- it’s a sloping roof if that’s important- and I have not planned to plaster it after- so is the answer solid board of some type cut to shape with a handsaw?View attachment 503969

fill it with roll or fill it with insulation board this is your choice

for speed its board i prefer roll on my own property

as goes for the boarding its your choice there about the same price between them all

so choose form plasterboard to 11mm osb board or soffit board 10-12" wide x 5m length

the one thing with plastic soffit board no painting needed

S

Thread 'Garage / workshop conversion'

Dec 27, 2022

I'm not really sure if this is the section for this or if there even is a section so please delete if not appropriate.

I have a larger than normal traditional single garage at my house. Its about 2.75m wide and 7.30m long. I have recently had the asbestos ceiling removed and now I'm aiming to replace it and start making the space into a workshop space for my tinkering.

My question is has anyone on here especially a builder done any fit out on there garage who knows the do's and don'ts? The garage is a single brick construction with a flat roof consisting of joists and planks with a...

• Spanthefestaman
• Replies: 109
• forum: Architectural

 

[MetalMonkey]

cellotex/jablite - much more pleasant to install from underneath than fibreglass.

If you don't want to skim it, but still want to use plasterboard you can put a trim batten over the gaps and just paint it - if you arrange the boarding evenly it can vaguely look a bit like panelling.
Aesthetically acceptable for a workshop anyway.

 

[Smallfry]

What is the outerroof covering ? Looks like old fashioned non breathable membrane. Is there any ventilation for the timbers if covered ?

 

[addjunkie]

Inch or so air gap, fill rest with celotex type stuff, flush with joists. Foil towards you, tape the joints. The over the top with insulated plaster board. Lats over the joints or just tape them, cost of emulsion, jobs a good un

 

[Beanwood]

What is the outerroof covering ? Looks like old fashioned non breathable membrane. Is there any ventilation for the timbers if covered ?

It’s good old clay roof tiles.

 

[frank horton]

why do most wait untill after its built to insulate.....?
I like insulated steel roofing.....

 

[Smallfry]

It’s good old clay roof tiles.

Ah, so there are roof battens fixed across those rafters. In that case I would fix an inch batten on the sides of the rafters, pushed up against the felt, in order to maintain a gap, then tightly fit Celotex/Kingspan of a thickness to fill to the bottom edge of the rafters. Fix in position with some battens nailed across, or plasterboard if you like a lot of work.

Try and create some ventilation for the gap above if you can.

 

[Gareth J]

As it's not a lived in space, there is very marginal gain for putting in more than a small amount of insulation right on the inside. Enough to speed warm up time so you minimise investment in getting the space up to temperature.

A solid layer of 25mm celotex direct to the rafters held in place by a layer of plasterboard will help masses with warm up times. If you can do similar with the walls too it would really help.

If you're planning to keep it permanently heated, that's a different game with different returns on investment available

 

[Nomad]

^ as said by @Blobber in post 2

I got a van load of used 2" celotex insulation (from a school demolition) at my local salvage yard, cost was a very reasonable 50p for a 2x3 sheet. £50 got me enough to do my garage roof, dormer roofs in the house and my ex's large camper van.

I wanted warm, no condensation, looks were not important so I cut the sheets to fit between the joists in my garage and used 6" timber offcuts (cut from pallets) screwed onto the battens from below to hold the insulation in place. Battens were 6", 2" insulation was doubled up and left a 2" airgap under the roof for ventilation. I left both ends of the run open so there was an air gap at both ends to prevent condensation. The garage was attached to the house and the insulation turned it from a cold unusable space in winter into a decent workshop.