Garage Roof

paddyb

We have a big garage (20 x 18 feet) that is not attached to the house (it’s at the end of the garden with lane access). We had the roof done last year but had some issues with the roofer.

Currently it is a metal roof with a loose breathable membrane underneath. The problem is that some condensation still gets in and stuff gets wet.
It is well ventilated (you can see the air flowing around from the membrane movement).

Is there a diy remedy to the condensation or it is a matter of a different roof type if we want to keep it dry?

The Continental Op

I have an old garage with a tin roof. We put down a membrane then insulation then the corrugated iron.

No problems with condensation on the inside of the roof but the garage is just plain damp anyway and everything in it gets condensation on it.

listermint

paddyb wrote: »

We have a big garage (20 x 18 feet) that is not attached to the house (it’s at the end of the garden with lane access). We had the roof done last year but had some issues with the roofer.

Currently it is a metal roof with a loose breathable membrane underneath. The problem is that some condensation still gets in and stuff gets wet.
It is well ventilated (you can see the air flowing around from the membrane movement).

Is there a diy remedy to the condensation or it is a matter of a different roof type if we want to keep it dry?

Back to basics


Condensation is merely a visible demonstration of high humidity mixed with not enough ventilation to combat the humidity level. This produces wet surface on any cold surface allowing the humid air to condense back to liquid form that it came from.

So the solutions are

More ventilation

Or

Lower than humidity source.

More ventilation can be very difficult in a climate like ours short of leaving doors wide open..

So maybe look at moisture sources. Is the floor untreated? A painted dpc can do wonders. Are you washing or drying your clothes on there if so make sure they are particularly ventilated and filters are clear. Is there plants or any other source of moisture in the room try take them out.is it a gym ? If yes open windows and doors during and just after workout.

The roof won't have alot of impact to any of the above.

paddyb

The floor is painted but it was built by a previous owner do it don’t have too much info about it.

No washing or drying in there. It is only used for storage

The main issue is drips coming from the underside of the metal roof

Added a few pictures

paddyb

One of the pics is a duplicate, this is from the back outside

The Continental Op

So it looks like drips from the roof will pool on the permeable membrane and then come through?

paddyb

The Continental Op wrote: »

So it looks like drips from the roof will pool on the permeable membrane and then come through?

Yes that’s right

The Continental Op

If you were to do the roof again you can get panels that are fully insulated. At the least you need panels that have a anti condensation membrane bonded to the underside.

Anti condensation sheet roofing https://www.mcsroofing.co.uk/dripstop-anti-condensation/

Insulated sheet roofing https://www.bushburycladding.co.uk/insulated-roof-sheets

So you can see the difference in the two - think there is also a big price difference.

You may also be able to remove the membrane and paint the underside of the sheets with something that will reduce (won't eliminate) condensation.

Than as listermint suggest you probably need better ventilation.

paddyb

Thanks. In terms of ventilation- is it adding vents to the walls below the membrane?

The Continental Op

paddyb wrote: »

Thanks. In terms of ventilation- is it adding vents to the walls below the membrane?

Its air movement from inside to outside which is obviously balanced by air coming in. Vents at either end below the membrane would help but I'd also say you wanted something lower down.