Insulating my garage

I’ve not spent a great deal of time in the garage in the last couple of months. Mostly because the work shop is not so appealing when it’s really cold. Last year I struggled on, taking frequent breaks to hover over the space heater. But it was always a losing battle. This year the thought of the cold kept me inside working on Witter.
At various points I’ve considered insulating the garage, considering everything from putting up a plaster board ceiling and using loft insulation, to just using thin reflective foil bubblewrap stuff stapled to the rafters.

I would have loved to deck out the ceiling with boards and make a proper loft space. However the structure of my garage was built without that in mind. The ceiling joists are just 2x4s that span a little over 4 meters. Fine for just holding a roof structure together, but certainly not load bearing. I considered options to retrofit the strength necessary, but the cost and effort involvd would have been disproprtionate to the benefit gained.
Finally someone mentioned a local polystyrene firm that sells large sheets for insulation. This of course has the benefit of being very light. And a collegue that insulated his tin shed reported notable improvement with 25mm sheet.

So I got some prices and found I could buy a sheet of 50mm fire retardent polystyrene 1.2m x 2.4m for £7.98 ex-VAT.

My plan was to cut up the boards and stuff them between the ‘ribs’ of the roof structure (rafters?) Right up under the felt beneath the tiles. Thus retaining access to the space about the ceiling joists for a few bits and bobs I have up there. I measured up and calculated I’d need 12 sheets to do it this way. Just for comparison I worked out the cost of just covering the space with whole boards and it also required 12 sheets. So this week I placed my order and on Friday they arrived.


This morning I set to work. First measuring up the bap between ribs of the roof for the first one to fill, then cutting a piece to size.

After getting it up into the space, manouvering, finding it was too wide, bringing it down, adjusting, puting it back up and manourvering, finding it was too long…. i layed it down on top of the joists and started to re-evaluate my choices.


Whilst retaining easy access above the joists is theoretically useful, in practice I don’t really need it. And by laying the sheets directly on top it would be a) much faster and b) mean i won’t be heating the whole loft space. And c) mean I could seal the main wokshop from the ceiling space and the gaps where the roof rests on the walls. I’m told thes gaps are important and need to be there. This way I keep them open to the ceiling space but not to the workshop.



You can see here I’ve just cut some bits to stuff between the ceiling joists at the edges to cover the gaps.
It took about 2 hours to get all the boards in place. Of course doing it this way left me with 3 whole extra boards. I clealy should have planned it this way from the start. I just put all the boards up so in some places it’s 100mm thick.
This afternoon I need to put all the little making up pieces to seal off the rest of the edges.
Hopefully I’ll really feel the difference and be able to comfortably work in cold weather. I just need to decide what my next project is…
After I clean up all this stuff off the floor: