Sealing leaking (bunker) garage walls (+ dehumidifier)

[sploo]

Short version: I've got a leaking concrete bunker; should I use Zinsser Watertite on the walls, and a desiccant based dehumidifier?

Long version: I've been lucky enough to recently move into a much bigger garage space (approx 9m long x 3m wide x 2.1m tall). I understand the construction is 200mm thick reinforced concrete - because it's effectively a retaining wall for a tiered garden. As such, the rear and right wall are completely underground, as is some of the left wall.

The inside of the garage is faced with a medium density "breezeblock"; which I'm told isn't structural, but the guy did it because he didn't want it to look like a concrete bunker.

After some heavy rain, I've started to get some water leaking through blocks at the rear of the garage, with damp patches on the right wall. That, combined with the fact it's pretty sealed with the rolling shutter door, means I'm getting some mold growth on timber.

Getting ventilation at this time isn't going to be easy, and there's no practical chance of trying to seal the outside of the walls as they're under tons of earth and a patio.

Zinsser have confirmed that their Watertite product would be suitable, so I was thinking sealing the inside with that, and also running a desiccant based dehumidifier in there (starting with the dehumidifier until I get a free weekend to coat the walls).

I understand there are false wall options (build walls off the existing) but I can't afford to lose that much space.

Anyone got any experience either with such sealing products, or using a dehumidifier?

 

[RobinBHM]

If its a rough surface maybe a tanking slurry would be best.

The problem with dealing with damp proofing internally is that as you improve the waterproof nature of the wall it means water pressure will build up and try and force its way through a weak spot.

https://www.permagard.co.uk/basement-wa ... nt-tanking

Or drybase?

Or even cement / sbr slurry

Just a few options to consider. I dont know zinsser watertite so dont have experience to share

 

[sploo]

Thanks - I wasn't aware of those tanking slurrys. I see the Zinsser product also contains Portland Cement so I wonder if it has some similarities.

I see it needs rendering with something (e.g. sand and cement) and I'd rather not lose space in the garage (plus I'm not sure I could do that job myself).

Decisions decisions!

 

[MrTeroo]

I use this dehumidifier

https://www.amazon.co.uk/ELA-DD822-Dessicant-Dehumidifier-Laundry/dp/B003XPWPLG

It's ben running constantly for over five years now.

 

[sploo]

Thanks.

I've just today taken delivery of an Eco Air DD122 Classic. Looks like a good little unit, but I haven't had time to fire it up yet.

It came with a freebie of a combined thermometer and hygrometer. Likely not world class levels of accuracy, but it put a warm dry office full of computers in the 30-40% RH region, and rose to 69% this evening when I left it in the garage with the garage door open (and it's been a dry day). I've left it overnight and will take a look at the reading in the morning. Certainly I'm hoping the dehumidifier will prevent the mold growth once I fire it up.

 

[MrTeroo]

Try to use it with the supplied pipe and run it out to a drain.

I drilled a hole on a downward gradient through the wooden frame of my garage door. Fed the pipe through it into a drain hole outside.

Never need to worry about emptying it now.

 

[sploo]

That's my plan - though it is 200mm of reinforced concrete, faced with breeze blocks; so maybe something via the door frame will be wise.

 

[sploo]

Morning reading claimed 90% humidity, which strikes me as unrealistically high, but temperature was stable overnight at 10C.

Hopefully the dehumidifier drying the air, and putting out a little heat, will keep the place in good condition.

I'll hopefully fire it up this evening and see how much it collects, before sorting out the drain pipe.

 

[DeanN]

I've used the Watertite on my garage wall. My neighbour has soil above the dampcourse level, and the result was a mouldy corner in the garage. I gave it a good clean down, applied 2 coats of watertite, and problem solved. No smell and no mould. Nice eggshell finish as well.

 

[sploo]

I've used the Watertite on my garage wall. My neighbour has soil above the dampcourse level, and the result was a mouldy corner in the garage. I gave it a good clean down, applied 2 coats of watertite, and problem solved. No smell and no mould. Nice eggshell finish as well.

Good to know. Thanks.

I picked up 9 cans this evening; which I hope will be just enough to cover the whole of the interior. I suspect ~45m^2 is going to take a while to paint.

Having read up a bit more on relative humidity it makes more sense. 90% RH at 10C is not actually that that much water in the air, but it will result in mold. Hopefully the dehumidifier will start to bring that down, and its heat output will raise the temperature a bit (which will also lower the RH).

 

[sploo]

The dehumidifier is working well. It's certainly filling up pretty quickly, and is raising the temperature in the garage slightly.

At the moment I've got it near the rear wall (the one that's most damp) as it's blowing its exhaust against that wall. I may move it nearer the front of the garage at some point; in order to get the drain hose out of a small hole in the door frame.

I will need to remove some efflorescence from the blocks affected by leaking - and it looks like a pretty thick build up. Obviously I can't hose them down after using an etching solution, but I've seen references to using white vinegar (which I have). I might give that a go when I get chance.