[Closed] Garage insulation, condensation and shelving....

if you do insulate make sure that it's completely air tight or any warmer air from inside the garage will hit the underside of the roof and condense and the insulation will then stop it evaporating properly so you'll get rot/corrosion.

Insulation needs to be on top of the roof rather than underneath it i.e. rafters, insulation, board, covering. That way you get a "warm" roof.

that's what I thought Murray but if it's corrugated steel I'm not sure that's possible?

Keep an eye on the big dug ebay store, particularly the clearance section. I picked up a 2m x 2.4m x 0.6m 4 bay frame without chipboard for £50 recently; it was the 600kg rated stuff. I then got chipboard from the local diy store, cut to size for £30. If you don't need it right now, it is worth keeping your eyes on the ebay store for a while.

Wwaswas....I can't insulate above the roof panel. It is ribbed/profiled so would kingspan do more harm than good?

If you go for the budget shelving don't go for Bigdug. I just ordered 40 bays of it from shelfsave.com and compared to the Bigdug stuff we have at another branch it's much sturdier and a lot easier to put together.

rockhopper70 - you can still do it but do a google search for 'cold deck flat roof' for information about how to avoid condensation issues between the insulation and roof materials.

If you are going for a cold roof (which is probably easier with an existing tin roof) then you'll need to ventilate the gap between the insulation and the metal deck. That should stop condensation build up. It won't be as thermally efficient as a warm room though.

So, could use encapsulated loft insulation, the squishy stuff in the tin foil roll, jam it into the corrugations from below and hold it in place with chicken wire or something and staples?
That'd fill the gaps wouldn't it?

You will likely end up with a small gap here and there and the roof will be cold so water will condense. What's the problem with making a proper cold deck with a ventilated void?

Nickjb...tbh, I'm updating this at work so I can't spend too much time googling!
I'll take at look at what is needed but clearly it's not going to be as simple as I'd thought, and I'm concerned that the roof people suggest a solution that sounds like it will cause problems.

Harrumph.

you could talk to those companies that offer to spray insulation inside house roofs - they may do the same for your garage? If the woodwork etc is all ok you won;t need access to them.

My garage has the foil wrapped stuff inbetween the rafters and then it's paneled with hardboard to keep things looking nice. Never had any issues with damp - apart from when it leaked but I've replaced the roof since then!

As for storage, I built my own - ended up getting exactly what I wanted (funny that) and as it's over-engineered will cope with anything :o)

Is it not better to just ask for drip stop and save you the PITA this will likely be?

I give you exhibit A m'lud:

http://singletrackworld.com/forum/topic/condensation-in-the-mancave

As an update, I am going to use a cembrit concrete corrugated sheet. Looks just like the existing but longer and wider lengths so fewer joints. And, apparently, because it is less conductive, doesn't cause a problem with condensation.
Fingers crossed.

Also, said installer is proposing to use [b]plain coated steel[/b] where others have offers the sheets with drip stop. They suggest a 25mm thick kingspan layer to stop condensation which I should be able to do myself. [b]Anyone had problems with a drippy garage[/b]?

Night sky radiation problem with single skin metal roof sheeting.