Insulating a garage beam and block ceiling below our house

[Mark Fresh]

Hi

We have a garage underneath our house which spans underneath the hall and kitchen. The house is 25 years old and in the winter the kitchen gets cold, when we moved in 6 months ago we had an energy saving assessment, the main suggestion was to insulate the garage ceiling to reduce the cold that comes up through the floor, as well as try to insulate the garage itself. The garage it dry and doesn't suffer from any damp.

My questions are:
What's the best way to insulate the ceiling? I assume it's to fix insulation boards to the ceiling and tape the joins but is there a technique to fix the boards up to beam and block? And which way should the boards go, foil facing down? Also what thickness? I know that the thicker the better but the thicker the heavier and harder to fix, so is there a "sweet spot" of thickness?

I've attached a picture of the garage if that helps. There are some strip lights which I will have to lower from the ceiling in order to fit the boards.

Thanks in advance
Mark

 

[Mark Fresh]

I've had a call from the Celotex Technical Support team (I sent them and Kingspan the same questions above). I need a (something beginning with R) value of 0.25 and so 80mm thick GA4000 (so that's known as GA4080). I can fit it directly to the ceiling with mechanical fixings and/or batons, no need for an air gap. I've not heard back from Kingspan yet.

Now to find the best price for 11 sheets of GA4080 in Canterbury, any suggestions welcome.

 

[endecotp]

You'll probably want a solid layer under the insulation, i.e. plasterboard.
One option is to buy plasterboard laminated onto insulation, e.g. Celotax PL4000, the other is to fit separate layers.

 

[CJRatch]

A great link cjard posted in another thread, http://www.secondsandco.co.uk/. Its seconds insulation board, not used before. Well worth considering and they deliver.

As far as fixing you've not got much choice but to buy a good masonry bit and get drilling. Use easy drive screws (They dont require plugs so you dont have to keep removing the board) with large washers and your away. Foil tape the joins and you've a nice vapour barrier to.

 

[Mark Fresh]

Thanks gents. CJRatch, do you mean these screws http://www.screwfix.com/p/easydrive...ling-roofing-screws-5-5-x-85mm-100-pack/4225h ? Would they be suitable to hold up the weight of the PL boards, they look like they're 30Kg each.

 

[Doggit]

As the object of the exercise is to insulate the roof, and not to make it prettier than it currently is, using insulated plasterboard is an expensive waste. Treat the job as external wall insulation, and just use ordinary celotex boards, and fix into the blocks (not the beams) using EWI fastenings https://www.amaroc.co.uk/products/wkret-met-lmx-10mm-x-90mm-with-metal-pin-qty-200

 

[CJRatch]

Thanks gents. CJRatch, do you mean these screws http://www.screwfix.com/p/easydrive...ling-roofing-screws-5-5-x-85mm-100-pack/4225h ? Would they be suitable to hold up the weight of the PL boards, they look like they're 30Kg each.

If you really want to go the insulated plasterboard route enough of these http://www.screwfix.com/p/easydrive-countersunk-concrete-screws-7-5-x-120mm-100-pack/9008h will hold a 30kg board. Drill a 6mm hole, with a good impact driver send em' home. There will a good 40-45mm fixing into the block once its pulled up through the board slightly. How many I couldnt say but I know these give a great fixing having used them before.

As the object of the exercise is to insulate the roof, and not to make it prettier than it currently is, using insulated plasterboard is an expensive waste. Treat the job as external wall insulation, and just use ordinary celotex boards, and fix into the blocks (not the beams) using EWI fastenings https://www.amaroc.co.uk/products/wkret-met-lmx-10mm-x-90mm-with-metal-pin-qty-200

All down to the original posters preference but I agree, its a garage, you've currently got block and beam on show, foil backed insulation taped up wont look much worse. Those fixings will do the job nicely if your just using insulation they work in a similar fashion to easy drive in that plugs are not required. Drill your hole, insert the fixing and hammer it home.

Totally down to you bud.

 

[endecotp]

Don't you consider insulation board too fragile to be the exposed surface?

 

[freddiemercurystwin]

Don't you consider insulation board too fragile to be the exposed surface?

Fragile why? Do you dance on the ceiling like Lionel Richie?

 

[Doggit]

The edges and joint will discolour slightly, but nothing more.