Lower ground floor flat with damp - where to begin

[vickylo]

Hi all

I'm a first time poster having discovered this site after watching Peter Ward's YT channel. Some really useful and thoughtful advice on here, and I'd be very grateful for any help or feedback anyone might be able to offer me.

I bought a part lower ground floor flat in September last year, and I've been having some problems with damp/mould/condensation. The worst affected room is my bathroom. I decided to take out the bath and remove the tiles from the walls to try and see what was going on. Here's a picture of how the bath space is looking now. A couple of things to mention:

- Previously, there was a piece of wood attached to the wall that was tiled to make a straight edge for the bath. This was fitted where the darker brown line is.
- The screws in a triangular formation are from a grab bar I removed when taking off the tiles.
- Some of the plaster came off when I was removing the tiles and other sections I have pulled off because it was wet and crumbling and hanging on by a thread.
- The particleboard sub-floor was wet through when I first took the bath out, which I think was, at least in part, due to defective silicone that was allowing water to run between the bath and the wall and onto the floor every time we had a shower.
- I've had a dehumidifer running 24/7 in this room for the past 3 weeks. When it's on, the humidity gets down to 40-45% (although it's got as low as 35%), but starts climbing again if I turn it off.



This is what that same wall looks like externally.


So obviously the ground level is quite a lot higher than the indoor floor level, the wall is rendered and painted and there's a pipe disappearing into the concrete. There are what looks like DPC injection marks under the window and then above each of the steps leading down, so I can't be the first person that's experienced damp here (although I would like to try and rectify it the right way!).

The building is Victorian with solid brickwork and suspended floors.

I suppose my question is: where would you start? Does it look like the wall has been rendered internally and should I do anything about that? Should I get a drain survey to see if that could be causing an issue? I know lowering ground levels is often advised, but would that even be possible with the steps (which are a RoW for the upstairs flats to the garden at the rear, so anything I do, I'd need to get permission for - and be convincing it was necessary!)?

All thoughts appreciated!

 

[malcolm]

That's tricky. The earth under the steps and path will be wet even when everything is working properly.

First thought is do you have a decent extractor fan in the bathroom? One that comes on with the light and keeps running for a few minutes until the moisture in the room is cleared would help. Also be careful not to dry washing inside.

It's nice to have a tiled wall in the bathroom but that would be waterproof. The exterior looks like render with waterproof paint so that won't let any water out. It'll just spread up and around the walls, cause damp patches and rot the floor joists above.

An interior stud wall might be a fix. If the wall were stripped back to brick and a stud wall infilled with PIR insulation infill was built with a gap to the brick wall then the water would have somewhere to go before it got to the interior. Downside is It would lose 5 inches of space from the room.

 

[a twig]

I had a similar situation in my old place, although it was a dining room rather than a bathroom.

Hacking off everything inside and re doing with an NHL based plaster helped a lot but still left staining as the internal evaporation of the moisture from outside would leave behind whatever mud etc had come in from the earth outside.

I was happy just to top up the clay paint periodically but my second step would have been to address the external issue:

It's about time for another high ground levels dilemma!

Bit of a puzzler - so image below - yellow is neighbour's property, green is mine, blue circle is where my water supply enters my property - there is also my gas pipe under there somewhere. On the inside of that wall with the green line is my dining room. 100 years ago there were steps, so most...

www.periodproperty.co.uk

 

[vickylo]

I replaced the extractor fan that was in there (a little old Manrose number) a few months ago with a Vent Axia one that is on continuous mode (but has a humidistat, so boosts when humidity is high and when the light is on and has an overrun of about 15/20 mins. But to be honest, it was pretty much always in boost mode).

The plan is to fully tile the bathroom - do you mean that this could be a problem?

Would it be possible to create a gap between the steps and the side of the building and would that even help? Sort of like this:



By the way, what is exposed no longer feel wet to the touch (but I guess that doesn't mean the brickwork isn't wet/the dehumidifier could just be drawing in the moisture).

That's tricky. The earth under the steps and path will be wet even when everything is working properly.

First thought is do you have a decent extractor fan in the bathroom? One that comes on with the light and keeps running for a few minutes until the moisture in the room is cleared would help. Also be careful not to dry washing inside.

It's nice to have a tiled wall in the bathroom but that would be waterproof. The exterior looks like render with waterproof paint so that won't let any water out. It'll just spread up and around the walls, cause damp patches and rot the floor joists above.

An interior stud wall might be a fix. If the wall were stripped back to brick and a stud wall infilled with PIR insulation infill was built with a gap to the brick wall then the water would have somewhere to go before it got to the interior. Downside is It would lose 5 inches of space from the room.

 

[Matt Green]

An interior stud wall might be a fix. If the wall were stripped back to brick and a stud wall infilled with PIR insulation infill was built with a gap to the brick wall then the water would have somewhere to go before it got to the interior. Downside is It would lose 5 inches of space from the room.

Once again I think Malcolm and I are thinking the same. Any plaster on that wall will be sacrificial, therefore I would be inclined to hack off the plaster and dry line it. Insolate any studs from the wall with a DPM (attached to the back of the studs, not the wall).

 

[malcolm]

The plan is to fully tile the bathroom - do you mean that this could be a problem?

It is sensible to tile a bathroom. A bathroom is not a good room to try to dry a wall into. My thought was the wall will be waterproof inside and outside. Water will get in from the ground and the earth under the steps and path and won't have any path out. Water will get in whatever. It's providing a path out that is important for avoiding interior damp.

A trench is a good solution but will only reduce damp above the level of the bottom of the trench. Below that level the wall will remain wet I did that to lower ground levels on one side of my house and the bottom of my trench is below internal floor level. But my external ground levels were only 12 inches higher than the floors.



An ideal solution might be to take out the concrete path and steps, finish the wall in breathable materials, then have metal steps fabricated so the wall can dry to the outside. That's a lot of work but not madly expensive.

 

[Cubist]

Hello Vicky(?) and welcome to this merry band,

Maybe its another sign of my advancing years and its impact on my sight but I'm not seeing much in the way of damp penetration from outdoors in the photo you included of the interior. All the damage that I can see seems typical of that caused by poor/failed seals around baths and showers such as those you have already discovered. However, before righting off your concerns about water penetration from outdoors, may I ask a few questions please?

I note that the bathroom is situated in a basement and the bathroom floor is approximately one meter below the level of the top step of an external flight of stairs that are confined by the bathroom wall on the one side and a retainer wall on the other. Is the top step of those at the same level as the street/road or are there further steps, not pictured, that descend back to street level? In other words, is the level of the street/road above or below that of the bathroom floor?

The reason I ask is that in the latter case that would indicate that waste water drainage from the soils contained between the retaining wall and the bathroom wall would be considerably better than it might otherwise be and that the main sewer lines are well below the level of the bathroom. Therefore, barring for damage to the waste water drains from your, or a neighbouring property, any water penetrating the bathroom wall from outdoors would likely be quite small.

Is the plaster that was behind the old bath in good condition other than for the damage done when removing the tiles? Is there any sign of the plaster becoming desiccated or are there any 'hollow' sounds when it is tapped lightly? If the answer to these questions is no, and assuming the old bath was in-situ for say 5 years or more, then its probable that you could get away with skim coat to provide a new smooth surface that could later be tiled.

Next question, why would you want this wall to breathe? The objective of encouraging respiration in any property is to expel moisture produced inside the house by our habitation. In the case of subterranean rooms, like your bathroom, its a trifle pointless as there is no way that the external walls can expel such moisture as the soils behind them is likely to be a darn sight wetter.

Sorry for all the questions but hopefully these will help to get you the right answer for your challenge.

Or.. am I just becoming more curmudgeonly as well as losing my sight?

Cheers,
Steve