Insulating Summerhouse with Celotex

[page3]

roofer said:

Keep a tarp over it. Too much sunlight will make it curl if its foil faced.

Stack it on edge also, not flat.

Thanks.

[page3]

First (largest) wall done. 50mm celotex packed between joists. Any gaps sealed with tape. 6mm ply over-boarded. The ply is a bit thin, but should be ok given that this is a summerhouse. Most of the time was spent moving the (surface mounted) plug socket, and feeding the cable (which is clipped to the joist) through a hole in the ply.

I found the celotex fine to work with, although I did use a mask just to be safe. Ended up cutting with an old kitchen knife, which I found neater than a saw.

Thinking forward, does anyone have any suggestions as to a decent primer to use internally on the ply, without costing a fortune?

[roofer]

Any water based primer/undercoat will do.

[page3]

It's taken a while, but I'm almost done...

Rubber roof.
Rub-down, fill and paint of outside.
Replaced and extended decking.
50mm celotex over-boarded with 6mm ply.
base sealant, painted.
1.8cm rubber flooring
air-vents
Electricity. LED lights.

Still got to do secondary glazing.

Mostly done by myself. First time DIYer

Before


After

[Simon.]

I will be interested to hear how this works with those big glass windows / doors at the front, have you done anything to those to try and limit heatloss via them?

[page3]

Simon. said:

I will be interested to hear how this works with those big glass windows / doors at the front, have you done anything to those to try and limit heatloss via them?

I’m intending on installing 4mm secondary glazing which will hopefully help. It’s never going to be perfect and I wouldn’t have chosen to start with this sort of summerhouse had it not been there when I purchased the house.

[Tinker2]

Resurrects very old thread as I’m about to do the same. Just had my summerhouse installed. About to do the same but for a garden office. Not sure if OP is still around - if you are how did it all work out?

[page3]

Still here

It was pretty successful, especially considering what we started with. Still looks good and is used regularly (or was before delayed hernia operations due to a closed NHS, but that’s another story).

No leaks or mould issues. In the winter we use a thermostatic radiator with a smart switch to limit heating to nights. We also use a dehumidifier when necessary, again on a timer.

It would have been better with a higher single pitched roof (to give more ceiling height) and less windows, but we had to work with what we had.

As a garden office you’d need to heat it more. For a gym keeping it cool is fine.

[eliot]

Might want to consider a mini-split AC unit, warms in the winter and cools in the summer.