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How do you add insulation to a garage or shed?

Insulation.jpegThe conditions for placing batts include the provision that there must be a gap between the external wall and the insulation itself. This is to prevent getting mould on the insulation.


You could also sandwich the current insulation that you have between Tunnelcore 2250 x 1220 x 2.5mm Black Double Walled Plastic Board, also known as Corflute.


I suggest cutting the Corflute into a rectangle that fits into the gap between the steel framing, place the insulation in, and then place another Corflute panel to the front. This will prevent the insulation from sagging and keep it away from the steel wall.


You can run zip ties through them to keep them together. It's like making a stiff insulation sandwich. - EricL

I have lined a few sheds. Glass bats need to be supported so if you use them on walls you will need to line the inside. The trick is to leave no gaps. In Tamworth I have used R2 and R2.5 in the walls and lined one with gyprock, the other with 12mm non-structual ply (can be screwed straight to steel frame and split aircon can be screwed straight to it).


When you buy your bats, foam or glass, remember they come in different widths so match them to your frame it saves a lot of cutting and wastage. Heat rises so once you line the walls most of your heat will be lost through the roof and any gaps it is important to insulate the ceiling.


If you are not putting in a ceiling I would look at insulating under the roof you can get fibreglass bats with foil on one side or foam this is where you will lose most heat. I would suggest R3.5 on the ceiling or under roof. Ring someone local who fits insulation and enquire (or go to a display home in the nearest town and enquire) or failing that I have been known to rock up to a building site and ask. - JDE

In our shed and studio we have used a product called aircell on the ceiling and batts in the walls. Although we haven't had temperature sub zero we believe they are doing a good job of maintaining a more comfortable temperature than without. - DIYgals

Cultivating a Following

Good article. You mention that "there must be a gap between the wall and the insulation itself  to prevent getting mould on the insulation".


Do you mean there should be a gap between the insulation and the outside wall or the inside wall?

Bunnings Team Member
Bunnings Team Member

Hello @Ritar


Thanks for sharing your question about the insulation. The gap is between the outside wall and the insulation. The purpose of the gap is to prevent thermal conductivity between the outside wall and the insulation. 


If you need further assistance, please let us know.



Workshop Legend

Another option if to use sarking type product such as this or at the very least a basic sarking product. They give you extra insulation and that moisture break. These products go on the outside of the frame before the cladding.

When you use insulation for any walls make sure you select wall, not ceiling, batts. These are denser so they will stand on their own and in most cases won't need strapping-in before the walls are sheeted.

Just Starting Out

@EricL - can you use spacers as a way to maintain the space between the external wall and the insulation? - similar to how you would install foil board?



Bunnings Team Member
Bunnings Team Member

Hello @prabzilla 


Welcome to the Bunnings Workshop community. It's marvellous to have you join us.


Depending on the type of insulation you'll be using, just keep in mind that you might need to use more spacers if the surface of the bat is too soft or flimsy. Whereas a batt with a stiff surface will not need as many spacers. Your reference to the foil board spacer is spot on.


If you have any other questions we can help with, please let me know.




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