Tin Roof Rain?

[Johnny7seven]

I've got a metal corrugated roof on my garage. When it gets cold condensation forms on the inside and drops of water drip from it down on to my tools and everything else soaking it.
Any solutions? Waterproof paint or something?

[davebro]

I would think insulation & ventilation are required.

[Fibonacci]

Some discussion on this topic here
https://forums.overclockers.co.uk/threads/metal-shed-roof-condensation-problem.18499810/

[KARL]

Remove the metal sheets, put down breather membrane and battens according to membrane instructions, reinstall metal sheets.

[Khandro]

Paint alone won't solve the problem, you really need a insulating false ceiling of some sort, are there wooden joists supporting the corrugated panels?

[KARL]

Alternative, depending on situation, would be to install closed cell foam insulation sheets (e.g. XPS) on the underside. Yet another option, but uncertain if appropriate in your case, might be to fix plastic sheet below the roofing, i.e. with a space between the two - this should at least reduce condensation on the inside of the roofing.

[bhg481]

You could replace the corrugated iron sheets with corrugated bitumen sheets from Wickes. I did my shed roofs some years ago because I was fed up with roofing felt expiring; no condensation problems.

[Johnny7seven]

I'm looking for a cheap option here. Seems I need to find a way to let warmer air escape. The roof slopes upwards. What about making an air brick by drilling holes in a brick at high level?

[TheDevil]

If you try using air bricks then I would suggest installing two air bricks at either end of the garage high up the wall. This will help create a draught allowing warm air to escape and be cooled down.

[davebro]

I don't think a few holes would do the trick. House roofs with non-permeable felting have (or have been retro-fitted with) multiple air vents. My flat has 4 vents back & front - 8 in total.

[The Builder]

No cheap solutions I'm afraid, Johnny.

As has been mentioned, "crossflow ventilation."
Something like a 9"x 6" (225mm x 150mm) every 1.2metres.

Pick two opposing walls, and fit them as high up as possible.

[KARL]

Another possibility: Move to somewhere that isn't as cold and damp ?

[Khandro]

The problem with the ventilation approach is that it will not only be very cold inside in winter, the OP also says he has tools in there, which will rust when the humidity is high.

You can help the problem by leaving the garage door open when your car is wet. All that water on & under your warm car is turning into moisture-laden air as your car dries.

[davebro]

Don't think he said he puts his car in the garage - most people don't!

If the roof is colder than the air inside there will be condensation if heating and/or ventilation are inadequate.

[Johnny7seven]

I actually do park my car in the garage (It's a double) and it's got garages either side.
What about cutting into the roof sheets and putting in louvre vents?

[The Builder]

Assuming it's a normal (i.e. almost flat) roof, johnny, you'll never rainproof around the vents. The pitch is too slow.

What about vents positioned at front and rear?

[Khandro]

Thinking outside the box, here's another route you could go down;
Amazon.co.uk User Recommendation

[The Builder]

That's a nice theory, K, and would work fairly well indoors.

The trouble is, in a garage, you would be de-humidifying the whole planet as it draws in air under the garage doors.

[Khandro]

Block the gaps! outside air comes into a house as well :0)

[Khandro]

Builder, also, it isn't working like an extractor fan, i.e. sending air out, it's only re-circulating the air already present - na na na-na na :0)

[Johnny7seven]

The dehumidifier is not a bad shout. What are they like on electric?