I have a new garage roof which is felted, with exterior grade ply as a base. I am getting condensation on the inside of the roof on the ply. The guy who fitted roof says he can coat it with varnish but that I will then get drips, which I do not want. Is there anything else I can use which will not cause drips but will stop the ply deteriorating because of damp?

Roger, February 2013

Insulate the inside of the ply roof with fibre-glass or similar and "face" it with something cheap.

Try to prevent steam or just warm, wet air entering the garage

Allow the car to cool down before putting it in the garage

Give the garage some ventilation from time to time

Your challenge is to stop the condensation

Peccavi, February 2013