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Damp hole of a garage
Stuart Walker - 16/1/23 at 03:36 PM

Hi all,

I'm really lucky to have a nice garage, but every time I go in at the moment it's quite depressing - everything ferrous has surface rust on it, everything wooden is green and furry, and anything leather or fabric looks like a rotten mess.

The walls are block on 3 sides and OSB panels on the fourth - the wood is the source of damp so that needs sorting by either building a proper wall or some damp proof layer. Assuming I'm going to do that anyway, what would your next priorities be?

- Insulate the roof? (it's currently single sheet aluminium)
- Put windows in to bring a bit of warmth in? (would be pretty easy as the top of one gable end is single sheet)
- Some sort of mechanical ventilation /a fan?
- Heat it? I'm reluctant because of the cost and it's never really that cold in Cornwall - just bloody wet

I like the idea of using a water wheel in the drainpipe to drive a ventilation fan! But I know it's never going to generate a enough power. Maybe as a switch though.

Cheers


roadrunner - 16/1/23 at 04:08 PM

I would look at ventilation.
It's backward, I know. But you need holes everywhere to allow the air to move around.
If you insulate you have to air flow behind to remove moisture.


SJ - 16/1/23 at 04:15 PM

quote:
Originally posted by roadrunner
I would look at ventilation.
It's backward, I know. But you need holes everywhere to allow the air to move around.
If you insulate you have to air flow behind to remove moisture.


I agree. both my part concrete part wooden garange and my carport are very drafty but I have no problem with damp and stuff doesn't go rusty.


indykid - 16/1/23 at 10:08 PM

You want one vent high, one vent low on opposite walls. There'll always be a temperature differential between inside and outside so it'll always drive airflow.

SWMBO's pottery shed, with polystyrene insulated walls, trapped enough moisture make the walls mouldy before I put a vent in the back wall opposite the door. It's stayed perfectly dry since.


Stuart Walker - 16/1/23 at 10:11 PM

Thanks all, great help, much appreciated. That's exactly what I'll do. No Locost deserves a mouldy steering wheel.

Roll on summer...


CosKev3 - 16/1/23 at 11:31 PM

Moisture traps work really well,can buy the disposable ones pretty cheap from the discount shops.


snapper - 17/1/23 at 06:56 AM

quote:
Originally posted by Stuart Walker
Thanks all, great help, much appreciated. That's exactly what I'll do. No Locost deserves a mouldy steering wheel.

Roll on summer...


Or a soggy bum


tegwin - 17/1/23 at 04:18 PM

Insulation and ventilation…

The metal roof won’t help, I’d replace it with a warm roof structure with minimum 50mm celotex type insulation.

I battened, insulated and osb the inside walls with a gap to allow air to flow. It’s now nice and toasty and dry


Stuart Walker - 18/1/23 at 09:26 AM

Thanks, that's what I was thinking - I had a look earlier and the timber roof structure would be pretty easy to add this to. And Celotex looks so much nicer to work with than the Eko roll stuff too!

Thanks again all

quote:
Originally posted by tegwin
Insulation and ventilation…

The metal roof won’t help, I’d replace it with a warm roof structure with minimum 50mm celotex type insulation.

I battened, insulated and osb the inside walls with a gap to allow air to flow. It’s now nice and toasty and dry


JoelP - 18/1/23 at 06:16 PM

Breather membrane and some cladding over the osb.


tweek - 19/1/23 at 10:32 AM

Don't forget about lighting. Some good lights and white walls can make a big difference.


coyoteboy - 19/1/23 at 02:33 PM

I'm going to go against the grain here.

Ventilation only works if your air source isn't hugely damp. Traditional house based advice/thinking is that a building has a higher humidity inside, and ventilation removes that damp air so it can't meet and condense on the cold hardware.

However garages rarely have a damp source inside (like a shower, or humans sweating). I have a similar situation, but my garage has massive ventilation, gaps under the doors, eaves open to the air, ridge line basically open so a gale blows through and I get leaves and branches in on stormy days. My CNC gets *coated* in moisture in the mornings because the air outside is the same as the air inside - about 90% relative humidity and the hardware got cold.

My solution was to seal all the ventilation, add insulation, and leave a few networking hardware items running to raise the temp a little. It's been a LOT less damp since then. IT just doesn't make sense to ventilate with high humidity air.


JoelP - 22/1/23 at 03:32 PM

Plus probably cheaper to seal and run a dehumidifier.


tegwin - 22/1/23 at 04:19 PM

If you go for a warm roof I can highly recommend EpDm membrane on the top. Easy to work with and long lasting. If you need any photos of a warm roof being built, U2u me an email address and il share photos of my garage roof rebuild.


cliftyhanger - 22/1/23 at 04:27 PM

recently my carport has been getting condensation on the roof. And yiou can't get much more ventilated than a car port!
I do have a steel roof, and a few sections of opaque fg for natural light. Which don't seem to suffer.
I am seriously thinking of coating teh underside of the roof with something (stonechip?) to give it a smidge of insulation. The temp difference between teh room and teh air under must be tiny, but the only reason for condensation to form.
However my garage has a 18mm OSB roof and a fibreglass coating. Brick built (single skin) and has zero hint of damp. Bare steel takes ages to gain surface rust. But that garage has resonable ventilation, no insulation whatsoever. Guess the OSB does the job.


James - 24/1/23 at 10:41 AM

quote:
Originally posted by tegwin
If you go for a warm roof I can highly recommend EpDm membrane on the top. Easy to work with and long lasting. If you need any photos of a warm roof being built, U2u me an email address and il share photos of my garage roof rebuild.



I've just done a warm roof on my utility (previously a cold roof). We had 3 buckets in there for the leaks, the paint was peeling and slugs were coming in.

I used EPDM too and agree it's great stuff for the inexperienced roofer.

I didn't scrimp anything (including getting half the celotex free) and it was still a pretty expensive project. I probably spent £3k-3.5k on it for a 5m x 2.2m roof.
However, I have enough 'stuff' left over to do another roof!

Get on Youtube and lookup Steve Roofer's channel. Absolutely fantastic resource.

Also, rubber4roofs.co.uk has a great collection of how-to's on their site and youtube. I bought everything from either them or roofingsuperstore.co.uk (I think). Just be warned as some things from superstore took a lot longer than promised!


If you go down the EPDM route can I suggest you wait for warmer weather. The rubber and corner trims and adhesives will all work much better with a bit of sun on them!


Stuart Walker - 25/1/23 at 05:30 PM

Thanks again everyone, some great advice here! The garage has plenty of gaps now I properly look at it so I don't think lack of ventilation can be the main problem. That said I'm going to add some proper vents to ensure there's a clear low-in high-out route. I've also bought a cheap humidistat, I reckon I might ultimately use it to control a heater and/or fan.

I put a couple of little windows in one end and even that has made a big difference, so I reckon I'll stick a big one at the other end and see if that contributes to keeping it a bit warmer. Sorting the roof above the wooden wall next, which I think is probably the crux. Insulating and OSB is on hold for now but I think I'll go for it in the summer, just want to do the under 100 quid jobs first and see what difference that makes. When I do I will take on board your EPDM advice, thanks a lot