Wet Walls and Floor in Single-Skin Garage

[robtuck]

I'm looking for some advice on stopping my garage from getting so wet. We've lived in this house for about 6 years, and until now we've only used the garage for storage, but we'd like to start using it as a workshop and home gym. The house is a bungalow built in the 1950's, and the attached small garage looks to be a DIY job, built later to the side, but it is also very old itself. It's made with a single skin of rock-face concrete blocks.

We've had the roof and guttering replaced, and we're having a UPVC back door/window fitted soon, along with a new sectional garage door. As far as 'sealing' it from the elements goes, I think we've done as much as we can. However, the walls are often visibly wet, and after very heavy rainfall, the floor gets very wet.

I'm assuming that the rain water is soaking in through the bricks, running down the inside of the walls and out over the floor. I've done some research, and there are various sealing paints and tanking solutions that seem to be suggested, but they all assume that the bricks are bare. The interior and exterior walls of the garage have been painted, possibly several times, and its very old paint, so I'm dubious about being able to remove it without causing damage or costing a fortune.

Are there any cost effective solutions to this? We've already spent a decent amount on the doors and roof, so short of rebuilding it, which isn't really an option at this point, I'm out of ideas for stopping the water. I'd appreciate any advice.

 

[cdbe]

First thing to check is the outside floor level, often it's the same or higher than internal and water will just run across. There are various tanking solutions that will stick to sound painted substrates.

 

[Harry Bloomfield]

First thing to check is the outside floor level, often it's the same or higher than internal and water will just run across.

In which case, raising the level of the floor of the garage should fix it.

 

[JohnD]

The interior and exterior walls of the garage have been painted, possibly several times, and its very old paint, so I'm dubious about being able to remove it without causing damage or costing a fortune.

A jet washer will take it off. Tanking is not a very good solution. The walls should not be wet.

But more important, please show us some photos of the walls inside and out. Mark the ground level/floor level with chalk to show relative heights.

Include the gutters, downpipe and drain, and the door opening, showing the slope away from it that prevents rain running in.

 

[^woody^]

A good quality masonry/render paint should provide enough water resistance externally.

Some silane water repellents can be used over paint - TDS-Paint-Sealer-2017-1.pdf (netdna-ssl.com)

You could polyethene the inner face and dry line the walls, and follow suitable detailing at the floor and DPC junctions - see various garage conversion threads

 

[robtuck]

This is the side wall before my partner gave it a coat of sandtex masonry paint to make it look nicer. You can see the lead DPM folded over above the second brick.


We live on an incline, and the back of the garage is higher than the inside of the garage, as you can see in the other picture. Our previous builder destroyed the door by driving a mini digger through the garage, which is why it looks the way it does, but we've had this water issue since before then. Our rear garden is about 20m long and slopes towards the house. The ground on the other side of the side wall is not higher, but our neighbours house is about half a metre away on the other side of it.


You can see the damp patches, but sometimes there are actual puddles of water, and the walls themselves have water streaks on them, which makes me think this is more of an issue with the walls rather than water coming in at ground level. We are going to have the floor raised a little, as its a very poor and uneven surface anyway, but raising it to the height of the outside isn't really a practical option, as it would then be much higher than the driveway.

If we have to live with this, thats fine, but I'd like to do everything I can to minimise it at least, even if we can just avoid having little puddles! Thanks for your help and suggestions.

 

[JohnD]

We live on an incline, and the back of the garage is higher than the inside of the garage, as you can see in the other picture.

I can't actually see from your pics how th ground level compares to the floor level.

Where it is higher (as you say at the back) and probably where it is the same, you should dig out the earth against the wall, to below floor level, so water can drain away and damp earth is not against the wall. If you can't leave the trench open with a retaining wall, you can refill with large clean cobbles or pebbles (not gravel) because water cannot rise by capillarity up large clean rocks, the gaps are irregular and too large.

you need to line the trench with landscape fabric or something to prevent mud or soil washing in and filling the gaps so it becomes damp.

You can treat the exposed wall face if you want, but water will rise up from below unless there is a DPC, so better to leave it exposed so it can dry out by evaporation.

if you want to raise the internal floor level, lay a tray of DPM, turned up against the walls to prevent moisure running onto the new floor. If necessary, you can build a low wall on the inside, standing on the new dry floor, holding the dpm against the damp wall so any moisture will run down behind it, and protecting the DPM from damage, tearing or disturbance.

You mention the outside walls being wet but you didn't include any pics of the roof, gutter or downpipe, so no idea why.

 

[Harry Bloomfield]

You can see the damp patches, but sometimes there are actual puddles of water, and the walls themselves have water streaks on them, which makes me think this is more of an issue with the walls rather than water coming in at ground level. We are going to have the floor raised a little, as its a very poor and uneven surface anyway, but raising it to the height of the outside isn't really a practical option, as it would then be much higher than the driveway.

You probably only need to increase the floor height, by a little more than the depth of the puddles you get inside - if the issue is due to ground levels, rather than wall ingress.