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willidh

Hi All

We have a small shower room downstairs that smells of damp.
It has a shower, toilet and wash-basin.
The walls and floor are tiled; the ceiling is plasterboard.
There is an extractor fan in the ceiling that takes the air into the eaves upstairs (via a flexible duct)
One of the walls is exterior - the other three are interior.

If we leave the shower room door closed for a few hours, a damp smell starts to appear.

We don't actively use the room at the moment - so it's not like someone is taking a shower and not leaving the extractor fan on for long enough.

Three plumbers have taken a look and can't find a leak. They have each told me that small, tiled rooms can develop a damp smell. But I'm not convinced. If there isn't any water flowing, as the room isn't being used, then where can the smell come from?

So I thought I ask the wider community to see if you all had any insights.

Thanks in advance,

Danny
 
Could be previous water ingression through the tile joints and the substrate got soaked, then as it dries you get the damp smell from substrate mould.

Check your grout/silicone joints for signs of mould
 
Are you sure the ventilation is working correctly? Is it a continuous running extractor or just a on/off with a light switch?
 
As previously mentioned, water can soak into the walls and evaporate out slowly. The water in your shower and basin traps can also evaporate. Your extractor fan might not be man enough to get rid of all the moist air up into the eaves, leaving moisture inside the flexible duct, which would evaporate also. In a small room with little air flow and tiled walks that can soon lead to a musty damp smell.
 
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If your not using the shower room for long periods it could be the waste traps have dried out or stagnant run the shower and basin for a few minutes each.
 
How old is the property?

What type of damp course does it have, blue brick, felt, injected?

Is the shower unit /mixer concealed or on the surface, are any pipes around it buried in the wall?

Is it a tiled floor or plastic tray?

If it was poor ventilation, you'd see mould on the tiles or plaster.

It's either a leak or damp coming up thro' the floor or walls.

The smell isn't appearing after the door is closed, it's always there and is just building up to a noticeable level.

You are probably getting accustomed to it, if you ask a non resident to have a smell after the door has been open for a while, they will be able to smell it.
 
A damp smell doesn't always point to a leak. A damp room can just be a damp room!
As most have mentioned check tile grout and may be worth while redoing with waterproof grout.
Maybe upgrade your extraction and ensure has a time delay of at least 15 mins so keep running after use.
Make sure drains clear and maybe use a drain cleaner/freshener.
Give whole room a once over with anti-fungal cleaner.
 
Thanks everyone for your replies and thoughts - here are answers to your questions:

Are you sure the ventilation is working correctly? Is it a continuous running extractor or just a on/off with a light switch?
- Not certain that it's working correctly. The fan is only on when the light is on (not even a timer!)

How old is the property?
- Built around 1950 with a complete renovation and large extension in 2008

What type of damp course does it have, blue brick, felt, injected?
- No idea - is there an easy way to tell?

Is the shower unit /mixer concealed or on the surface, are any pipes around it buried in the wall?
- The mixer is on the surface - the pipes are behind the wall. The hose from the mixer to the shower head is a standard hose.

Is it a tiled floor or plastic tray?
- The shower is a raised plastic tray. The floor of the shower room is tiled. I have removed the inspection panel to check under the shower tray - it's bone dry.

If it was poor ventilation, you'd see mould on the tiles or plaster.
- No mould as far as I can see
 
Thanks everyone for your replies and thoughts - here are answers to your questions:

Are you sure the ventilation is working correctly? Is it a continuous running extractor or just a on/off with a light switch?
- Not certain that it's working correctly. The fan is only on when the light is on (not even a timer!)

How old is the property?
- Built around 1950 with a complete renovation and large extension in 2008

What type of damp course does it have, blue brick, felt, injected?
- No idea - is there an easy way to tell?

Is the shower unit /mixer concealed or on the surface, are any pipes around it buried in the wall?
- The mixer is on the surface - the pipes are behind the wall. The hose from the mixer to the shower head is a standard hose.

Is it a tiled floor or plastic tray?
- The shower is a raised plastic tray. The floor of the shower room is tiled. I have removed the inspection panel to check under the shower tray - it's bone dry.

If it was poor ventilation, you'd see mould on the tiles or plaster.
- No mould as far as I can see

This is your main problem.
A small enclosed shower room requires decent extraction or you will have dampness.
At the very least you need upgrade your extraction to at least a time delay fan and even one with a humidistat that will run when there is humidity in the room.

eg. Manrose Axial 20W Bathroom Fan IP24 | Screwfix.com
 
I wonder if the extractor is feeding steam onto a wood or other absorbent surface in the loft, which becomes saturated when the shower is used, and then feeds the smell of damp back down through the ducting.

Trying running the shower for a good period of time, and than after switching the extractor off , seal it up using cling film.

If you don’t then get the usual smell of damp, you will know where the problem lies.
 
This is your main problem.
A small enclosed shower room requires decent extraction or you will have dampness.
At the very least you need upgrade your extraction to at least a time delay fan and even one with a humidistat that will run when there is humidity in the room.

eg. Manrose Axial 20W Bathroom Fan IP24 | Screwfix.com

I agree. A flexible duct with it's corrugated sides provides an awful lot of surface area for airborne moisture to condense on. I'd bet only a tiny percentage of moisture is actually being taken outside. A powerful fan will be able to shift the water vapour (heavier than air, remember) better, and a longer running one will dry the walls of the duct by passing air over them and re-evaporating any dew that's formed on then.
 
Could be previous water ingression through the tile joints and the substrate got soaked, then as it dries you get the damp smell from substrate mould.

Check your grout/silicone joints for signs of mould

Why didn't you just say 'check your grouting, water leaks down the back of the tiles'

I had to get someone to translate the first part for me.....
 
I agree with Dave1

The 'damp smell' your smelling might just be coming from the drains, eg/trap seal loss or a dodgy anti siphon vent on the basin trap.

Are the ceiling and grouting all black and mouldy?

Also is there a carpet in the shower room? Many a bad smell can be traced back to a rancid carpet around a toilet.
 
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There is difference between the smell of damp when it regularly dries out, and the musty smell created by mould when it forms due to a permanently damp surface.

Try the cling film test over the extractor fan - it won't cost you anything.

It would probably be better to extract the steam through the exterior wall, than have a lot of ducting involved up to the loft.
 
The extractor fan might be not powerful enough to take the dampness out of the bathroom as well as rising damp from the ground. You may do not have a damp proof barrier which causes a lot of trouble. If you do not have a damp proofing it's highly likely that the damp rising between your tiles and causes a smell. If that's the issue you may end up having mould on silicon and tiles and one day tiles getting loose and week.

You could do some damp proof injections if that's the case but also too check your traps as mentioned in previous threads. But also check the power of your extractor fan it might be not powerful enough , I had the same problem few years back I had only 30!liters a minute wasn't really enough so I bought a 90 l/m.

You also could try to dry the bathroom out with a dehumidifier it may help.
 
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