Damp Garage

Evening all, so question for you knowledageble folk!

So our house is a couple of years old, and part of the appeal when we bought it (well, for me anyway, the wife couldn't care less!!) was a reasonable size detached garage (with plenty of storage above for my addiction to buying Puma parts!) built in the same engineered stone as the house:



Before starting the restoration of my FRP last year, I painted the floor as it was always really dusty, but accepted maybe the slab wouldn't be 100% dry with it being a new build. I noticed that the garage was getting really damp, even the lovely new vapor blasted sump on the engine started to show signs of corrosion. The units on the wall started to bow in the middle as the carcasses were getting damp too.

This warm summer I thought everything will dry out and maybe this year it won't be so damp, but a couple of days of Baltic weather in not so sunny Yorkshire and the damp is back, these are my tools - you can see the difference between the rachet I've just put back in the box compared to the others that are covered in condensation.

So, long story short, any ideas how to try and keep the damp at bay? You can even see feel the condensation on the floor....

Hi James
Maybe a bit of ventilation in the soffits of the garage might help. I f it's been very wet around here I can go in my garage and the floor's wet even though it's concrete slabs, a layer of sand and then concrete flags on top. if it's dry outside and I leave the doors open a couple of hours it soon dries it out.
Barry

Lots of variables/unknowns here and answers kinda depend on what you got there and what sort of "fix" you prepared to do... for instance, do we assume it is watertight and not leaking? If so, what's the construction? Is it single skin, if not has it got a DPC for instance? If no DPC then put one in. If it is single skin then (as well as decent ventilation) look at tanking walls, then maybe battening. insulating and boarding, or just get thermal boards that do both.
Is the damp coming up through the floor at all, or you sure it's just condensation laying on it? If the former, it might not have a membrane (and if it does it looks like it needs work) so sort that. If the latter then hopefully sorting ventilation and a dpc/tanking etc will stop that. What's the roof like, insulated at all?
The cheaper option of course is to just move your tools :grin:

g-whizz said:

[post]358819[/post] Lots of variables/unknowns here and answers kinda depend on what you got there and what sort of "fix" you prepared to do... for instance, do we assume it is watertight and not leaking? If so, what's the construction? Is it single skin, if not has it got a DPC for instance? If no DPC then put one in. If it is single skin then (as well as decent ventilation) look at tanking walls, then maybe battening. insulating and boarding, or just get thermal boards that do both.
Is the damp coming up through the floor at all, or you sure it's just condensation laying on it? If the former, it might not have a membrane (and if it does it looks like it needs work) so sort that. If the latter then hopefully sorting ventilation and a dpc/tanking etc will stop that. What's the roof like, insulated at all?
The cheaper option of course is to just move your tools :grin:

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The tools would be the easy bit, it's all the parts that I'm worried about

The slab has a dpc, as do the walls. They are only single skin. The roof is pitched with a vapor barrier and concrete slates and watertight. It's just ruddy damp! I did think about batterning, then that silver bubble wrap stuff and boarding, but then realised that would cost a fortune and reduce the internal dimensions too. Kinda wonder if it's as Barry says and down to poor ventilation. No roof, soffit or air bricks....

As it's only 2 years old, Is the house covered by an NHBC 10 year guarantee, if so submit a claim.
Sounds like it's caused by poor construction.I am also wondering if the soakaway at the entrance is wide enough and working correctly?

XAF said:

[post]358816[/post]
So, long story short, any ideas how to try and keep the damp at bay? You can even see feel the condensation on the floor....

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Yep, simple enough and cheap to do and the trick is to do what gardeners need to do in their greenhouses overwinter. Apart from #1. So -

#1. That 'up and over' door is allowing too much water to come in underneath it. I have a brown, flexible DPC strip attached to the bottom of mine and it blends into the ground outside and stops all that, including driven rain (I'm very exposed where I am). Some people have a rubbery bump strip on the floor, but they are not that effective.

#2. As with greenhouses, ventilation is the key here and that falls into 2 parts - #a. where does all the excess moisture go? and #b. How to get the air inside moving around? In your circumstances, I suggest an extractor fan (about £25) on the rear wall for the first part and 2 x 30cm 3 speed rotating fans for the latter. The copper finish ones look good and are around £20 each and use 40W each.

If you have an average sized bathroom with an existing extractor fan then you can see the results for yourself in advance - wash a few big towels and a couple of towelling dressing gowns and don't tumble dry them. Hang them from a (strong!) line in the bathroom and turn just one of those fans on all night - by the morning they will be dry.

#3. 25mm holes at 30 cm intervals through the soffits - or through the brick where the soffits should be, is no bad idea.

#4. Forget any form of heating - dangerous when unattended and very costly.

#5. Dehumidifiers are fairly pricey, range from 200W to 1500W+ and cost a bit to run. They are also not over-effective below 65*F.

#6. If you haven't got one already, consider fitting a back door to the garage next Spring.

#7. Spraying anything metal with can after can of GT85 is no bad idea either. Garden tools usually get engine oil applied with a brush and I have a good few from Victorian times and they still look fine and never rust.

XAF said:

[post]358820[/post]
The tools would be the easy bit, it's all the parts that I'm worried about
... I did think about batterning, then that silver bubble wrap stuff and boarding, but then realised that would cost a fortune and reduce the internal dimensions too. Kinda wonder if it's as Barry says and down to poor ventilation. No roof, soffit or air bricks....

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Re. boarding etc. Looking at the inside of the garage from the photo it shouldn't reduce the internal dimensions too much as it would mostly go in between the block columns wouldn't it, so a couple of inches down either side really?

...and Barry is ALWAYS right, I suspect he's directly descended from Tiresias and The Oracle

Cheers for that Greg but I wish it was true and I'm also old enough
Garages aren't constructed to the same standards as houses and also not heated so condensation and dampness will always be a problem. Any valuable parts in thin steel I would store in a spare bedroom if you have the room and all the rest in plastic packing cases that are waterproof (I bought some at Rufforth last week)
Barry

I have similar problems with my detached garage. Put a thermometer in your garage and you’ll find the temperature is not much higher than outside, if at all.
You cannot expect anything else when a garage is unheated. In addition, you appear to have an uninsulated, single skin up/over door, and won’t have a decent seal around it. Even if you put insulation in, it’ll be like a big cool box, only able to hold the existing temperature for a period.
In addition, opening the door will allow ambient temperature in, and, in this weather, parking more than one ton of cold, wet metal in there, can only exacerbate the situation.
I doubt, you’ll have any joy with any NHBC 10-year guarantee, as a garage is built for parking a car in, not to living standards. I think you’ll need to get some better insulation in there, including a new garage door (double skin with thick rigid foam - not cheap) to keep any heat in, as well as supplementary heating to raise the ambient temperature. Unfortunately, as the garage is detached, you can’t, as a lot of people do, run a radiator in there from the house central heating, so that leaves some type of electric heater. In addition, a dehumidifier would help.
To summarise, the tools/parts are made of metal, as is your car, the garage is near ambient temperature, and how wet and cold are our cars on cold mornings?

Thanks all, brilliant ideas there and lots I could do that won't cost a fortune. Extractor fan and vents is a cracking starting point, rubber strip already on the bottom of the door!

Does the rubber strip work well? Water always gets under my door and anything near on the floor gets wet.

red said:

[post]358833[/post]
Does the rubber strip work well?

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The usual ones attached to the ground can help, but are not that great. Judging from XAF's pic above, the conventional ones attached to the bottom of the door are not very effective either. If you think about it, with those designs if they were truly effective in sealing then how would you open the up and over door?

Solution-wise, well, you can't beat pouring a watering can or two of water down a garage door to see how ideas work in practice. I cut a 5 inch strip of this brown rubbery DPC material and stuck it to the outside of the door around 2 inches up and then did a line of self tappers and washers. The remaining 3 inches then curls to form both a real seal and an 'apron' that carries water well away from the door, which still opens and closes fine. The material you choose for this does have to be able to curl though or you'd be in a world of pain - after a week or so, the 'curl' seems to set in that shape.

Stuff above I forgot to mention - viewed from outside, soffit holes should be drilled at a slight downward angle. Also, in garages and outbuildings - use 'sacrificial' old newspapers - they pick up moisture very easily and you throw them away every week or two.

Just needs a couple of tile vents that does

Dehumidifier.

I store all of my guitars in my parent's cellar and even in the wettest of wetness there's never any evidence of moisture, and one thing that will show it is a guitar neck! I can't rate them enough.

red said:

[post]358833[/post] Does the rubber strip work well? Water always gets under my door and anything near on the floor gets wet.

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The strip does work really well to be fair, I think it was called "Gap Stop". Used to get pools of water through the bottom, now even in driving rain it doesn't come in. Because of the shape the wind kind of forces it down. The pics I put on earlier were before the house was finished, hence why a car could fit in and there was no crap in it!!!

Door closed:



Profile:

XAF said:

[post]358865[/post] The pics I put on earlier were before the house was finished

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Ah, that makes sense now.

Your strip looks discrete and, more importantly, purpose made for the job. Years back, for the underside of those doors they only sold longer versions of, what were really, draught excluders for doors and they didn't work very well, so I'm told.

Yep, bit of ventilation in there and you'll be good to go. Keep your fan low and your vent (extractor) high and you'll be fine, which is the same principle that barns, granary stores, warehouses, etc have used for thousands of years (they had to rely on pressure differentials to get a good air flow and that's why barns are long and thin)

My sheds sweat in mild damp winter weather but the garage which is standard brick wall, felt flat roof, up n over door 16ft by 8 ft has a dehumidifier in it and has done for years and houses my XR2 which never suffers from rusty brake discs, white fur on the ally parts. It did go wrong for a month one winter and the gearbox grew white fur in places so I guarantee the dehum' works. The one thing my garage does have in its favour is the fact its well inside my carport so the door doeant get hammered by wind and rain.

This may help - I'm not sure..

Dan has a timber frame garage, which we insulated - walls and ceiling. Floor is concrete, painted. The door is a Hormann insulated sectional door with seals. In the winter we run a dehumidifier 24/7.

The end result - we keep bare sheet metal in there that does not rust at all. The dehumidifier on average removes about 10 litres every 10 days to 2 weeks. So even 'sealed' which it isn't completely air right, it's still removing a lot of water. Not too surprising when relative humidity in the winter is 90-99%

Funny how sometimes you forget to mention the obvious.

Anyway, something arrived from China yesterday that reminded me - https://www.amazon.co.uk/gp/product/B004GN9EH2/ref=oh_aui_detailpage_o05_s00?ie=UTF8&psc=1

I ordered it for an outbuilding a few weeks back, but these are pretty essential for anything relating to damp/humidity, otherwise you're just guessing all the time. Certainly a lot more accurate than using pine cones or bladder-wrack seaweed which people used to use.

This one is about 4 inches (10cm) square and is quite good and very cheap. Houses are around 40% usually and garages can be anything you like or can get, but certainly less than in the 80% - 90% - 100% range, as that is pretty damp.

Very good for seeing just how effective your preventative measures are.