Damp in Bathroom on bare ceiling – How can I dry it out?

[girlincity]

Please help!

I live in a 1960s flat with a bathroom with no window and an old extract fan. The flat upstairs has a bathroom in the same place, and we are separated by a concrete floor.

I am in the process of decorating my bathroom ceiling. It was covered in anaglypta lining paper which I have removed. As I removed the paper I realised that there was a layer of PVA glue sealer on the plaster. (Now, this sealer could have been the backing from the old lining paper, or it could have been purposely applied to the plaster). As I removed some of the paper, some of the sealer came off with it, so I thought it best to remove all the PVA glue from the ceiling.

(Regardless, I have been told never to apply PVA glue to plaster, as it blisters up when you paint over it, so I thought it a good thing to remove it all).

The ceiling is now bare plaster.

My problem is this:

I have suddenly realised that half of the ceiling is bone dry, and the other half (when you touch it) is cold and damp. The plaster is a shade darker on the ceiling above the bath area and extends a little beyond. The damp patch is permanently the same. I only shower once a day, and so I would expect the ceiling to dry out (or the damp to creep back a bit) exactly 24hrs after my last shower

I do not believe there is a leak upstairs, as I don't think that the water can seep through concrete.
And I would not expect the leak to cover the ceiling wall to wall as it currently does.

I always shower with the bathroom door open to let steam out.
I have a really old extractor fan from the 1960's, but this doesn't seem very effective – but even so, I would have expected the ceiling to dry out a bit after 24hrs.

Basically – how can I dry my ceiling out?

I'd be grateful on any advice as so that I can paint it once it has dried out. (Good quality bathroom paint of course when the time comes).

Look forward to your replies!

 

[AronSearle]

I assume the cold half is the half nearer the external wall.

The slab could be acting as a cold bridge and contributing to condensation, if this damp is only occuring near the walls this is more likely. It may then be worth considering installing insulation backed plasterboard (with in-built vapour control layer). Otherwise you will struggle to avoid condensation without almost permanent ventillation (think of those old fashioned window vents with holes inches in size in cold restrooms).

 

[noseall]

One possibility is to remove the dew point altogether by fixing insulated plasterboard (or insulation + plasterboard) to the existing ceiling, then re-skim.

The other option (or run this in tandem with the insulation) is to install a stronger extractor fan.

Incidentally, the reason for not applying PVA is that it prevents the paint from keying to the plaster.

Did one side of the wallpaper come away easier than t'uther?

 

[girlincity]

Hi AronSearle – Actually my bathroom is sandwiched between my kitchen and my bedroom. It is also backs on to the flat next door. So it is effectively cushioned by 3 internal walls. (The kitchen, the bedroom and the flat next door). (So there is no window in the bathroom).

Hi Noseall – Yes as a matter of fact the wallpaper pulled off very easily) in one big pull) on newly discovered damp side.

Any other advise now that we know that the walls are all internal, so no outside cold should be a factor?

I just want a nice bath!

 

[JohnD]

maybe the people upstairs have a leak.

tape a piece of clear plastic tightly to the ceiling, in the dry and in the damp part. Does water form on the plastic? Which side?

 

[AronSearle]

I'm confused.

It is between two rooms and backed to another flat, that is 3 walls, so what is the 4th wall?

Regardless if it is all internal I can't possibly see how it is condensation and must be a leak.

 

[girlincity]

The 4th wall is my hallway wall. So internal.
Oh cr*p. Really don't want to have to ask the neighbour upstairs to unscrew his bath panel, but will have to to eliminate from investigations.

 

[girlincity]

Untitled

• girlincity
• 7 Jan 2015
• 1

 

[girlincity]

Sorry. 4th wall is a bit of my lounge.

 

[girlincity]

John D – I have taped plastic to the ceiling and will let you know the outcome.