Damp / Condensation in garage with photos

Golaboots888 · 5 Dec 2008

Hello.

I've got a damp 1930's garage. The walls are sealed with some aquaseal and must be ok as the garage was fine in the summer (warm wet weather) but is now damp.

I suspect the roof is the cause of the problem, it is made from bitumen corrugated sheets. I think that perhaps the relatively warm air inside the garage condenses on the cold roof at night.

I was thinking of adding some insulation, either stapling some of this foil type stuff to the rafters
http://www.wickes.co.uk/FOIL-INSULATION/Thermal-Insulation-Foil-Roll/invt/210022

Has anyone got some advice on which would be best and if this is the right way to go? I was thinking of adding an extractor fan with a humidistat also.

Many thanks

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JohnD · 5 Dec 2008

might be water vapour rising up through garage floor

older garages and sheds did not have DPM under floors, it only became practical with the intro of polytrhene sheet in the 1970s.

the floor will be warmer than the shell of the garage, at night and on cold days. so misture will rise up throgh the floor and condense of roof and your nice shiny metal tools, making them rusty.

insulating the roof will stop condensation up there, and high-level crossflow ventilation wil help the most air to escape.

Golaboots888 · 5 Dec 2008

JohnD said:
might be water vapour rising up through garage floor

older garages and sheds did not have DPM under floors, it only became practical with the intro of polytrhene sheet in the 1970s.

the floor will be warmer than the shell of the garage, at night and on cold days. so misture will rise up throgh the floor and condense of roof and your nice shiny metal tools, making them rusty.

insulating the roof will stop condensation up there, and high-level crossflow ventilation wil help the most air to escape.

Not convinced if this is the problem, the floor is bone dry apart from where the consation has dripped.

Golaboots888 · 10 Dec 2008

I took out all of the expanding foam that had been used to 'seal' between the corrugations and the wall.

This doesn't seem to have helped

skylined_gtr · 10 Dec 2008

Have you tried putting a damp meter to the floor to see if it might be the case?

Also I certainly wouldn't employ any insulation of any sort until you find the cause of the damp. If as you say the problem got worse when you removed the foam from the roof where it meets the wall I think you'll need to put some foam back in, find another solution or switch to a different type roof.

Do you notice it is any more damp after a good rain?

PS I am not a builder, a DIY'r like most

JohnD · 10 Dec 2008

if you tape a piece of clear plastic to the floor, you will be able to see if damp is coming up from it because the underside will get wet.

Deluks · 10 Dec 2008

All that earth piled up against the back wall could be causing moisture to bridge the dpc, which might be a way for damp to get in, which then manifests as condensation.

andyandy2 · 10 Dec 2008

Are you using the garage for a car ? If so this is probably where you are bringing in all the moisture

Golaboots888 · 12 Dec 2008

Hello again.

The garage is too small for a car, so there's no moisture there.

I'll have a go taping some clear plastic to the floor to see if thats where the problem comes from.

The walls are sealed with aqua seal so I don't think moisture is coming from there.

It seems to be worse in cold weather rather than wet which kind of supports the condensing on a very cold roof approach.

That said I 'borrowed' a space blanket out of the house loft and pegged it to the roof of the garage and although no condensation on the bottom of the space blanket there does seem to be just as much between it and the roof, damn corrugations.

Any more ideas?

big-all · 12 Dec 2008

are you working in there or putting warm things in there!!!

suspect you have your own micto climate in there

warm moist air rises and as the roof cools the water condences on the unerneath runs down the roof till it hits a supporting timber or the lowest point

removing the foam hasnt worked because the air has no where to go you need a vent on another wall and if its a large area you will need more to stop stagnent corners

Golaboots888 · 12 Dec 2008

big-all said:
are you working in there or putting warm things in there!!!

suspect you have your own micto climate in there

warm moist air rises and as the roof cools the water condences on the unerneath runs down the roof till it hits a supporting timber or the lowest point

removing the foam hasnt worked because the air has no where to go you need a vent on another wall and if its a large area you will need more to stop stagnent corners

I do spend some time in there so ventilation could be key. The garage is only 2.4m x 4m, perhaps some weep vents woudl help, although there is no access to one of the long walls.

Perhaps weep vents along my long external wall and an extractor high on the rear wall would pull enough air through.

What do you reckon?

JohnD · 12 Dec 2008

Now you have put the photos up, I agree with Deluks. Wet earth piled up against the wall will mean the wall is wet.

big-all · 12 Dec 2008

Golaboots888 said:
I do spend some time in there so ventilation could be key. The garage is only 2.4m x 4m, perhaps some weep vents woudl help, although there is no access to one of the long walls.

Perhaps weep vents along my long external wall and an extractor high on the rear wall would pull enough air through.

What do you reckon?

any sort off ventilation will help

i used to work in an area 6ftx12ft with a plastic roof i had to put bottle caps on the wire above the bulb holder with the top half of the bottle screwed on
the light switches and sockets had heavy duty plastic bags screwed behind then folded over the top with blankers covering the power tools to keep the damp out and soak it up
the blankets where hung out to dry each day and recovering the tools at night

Golaboots888 · 15 Dec 2008

A quick update.

I tried the clear plastic on the floor test and there is no sign of water coming through here.

I spent saturday putting in some weep vents, 10 in all along the long side of the garage.

Things seem to have improoved in part. I was going to add a couple of air bricks high up on the opposite side. I'm also going to instll an extractor to pull some airthough once a set humidity is achieved.

I'm not convinced the soil is causing the problem though, the walls are damp proofed with some tar type paint on the inside.

Perhaps if the extractor doesn't slove the problem I'll spend an afternoon with a spade and some damp proof membrane and seal what I can on the outside.

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Damp / Condensation in garage with photos

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