Damp/Mould on ceiling. What could be the cause?

adocholiday

I've recently bought a house and since we moved in ~12 weeks ago some damp and mould has been forming in the ceiling of the en-suite off the main bedroom. I'm trying to get to the root cause of it and will give you as much info as I can. Apologies in advance for the wall of text. The house is a single-storey south facing bungalow and the en-suite is at the back of the house.

We bought the house in the summer so when the inspection was done by the engineer there was no sign of any damp issues due to the dry, hot weather. To be clear there are no damp issues in any other room of the house.

The weather was pretty wet in the weeks following our move-in and after a few days of continuous rain I noticed that there was a golf-ball sized hole in the fascia, exactly where the worst of the damp is. I attributed the damp to water ingress there and have since lined up someone to replace the wood and gutters next week. In the meantime though the damp has continued to spread even though we've had little rain in the past few weeks. Also the roofer has said that he doesn't think that the hole would be responsible for the damp in the room.

In the past few days I've really noticed that the bedroom now even smells and feels damp. When I wake up in the morning the top of the duvet can actually feel clammy to the touch. However there are 2 other bedrooms all along the back of the property and there is no sign or smell of damp in either of those rooms. In addition to that, the water storage tank is in a crawl space in an attic conversion right over the main bedroom and there's a kind of musty/damp smell in there, but I guess that's probably somewhat normal given that there's a big plastic tank of water in there with pipes coming from it. I couldn't see any obvious issues there either.

The en-suite is carpeted (I know... being replaced with tiles soon) and has no extractor fan. There is however a small window with a trickle vent in the room and I do try to keep the window open as much as possible. The bedroom itself is unaffected in that there's no obvious damp on the walls or ceilings but definitely a musty smell. There is a large double door and window in the room too which can have heavy condensation in the mornings. There's only a small wall mounted electric heater in the room for heating.

Finally there doesn't seem to be any water pooling outside the walls or that on wet days and the site is about 10 feet above the road so the drainage is good.

I'm just hoping that it's a combination of the carpet absorbing the moisture in addition to a lack of good heating and ventilation but I'm more concerned that it's something more serious. Anyone have any suggestion into next steps of investigation?

Metric Tensor

Mould in an en-suite is almost always due to lack of ventilation.

The most used shower in the house is probably in that room? Scrub it off for now and push the window wide open when you shower and for 15-30 minutes afterwards for the next while and see if it helps.

Medium term you need an extract fan.

Obviously there are other causes too but generally three things are needed - moisture, lack of ventilation and a cold surface for water to condense on.

BryanF

As above clean the mould and add vinegar - a fresh start so to speak.

Then,
Get an extractor !

Until you do, buy a RH sensor (Amazon 20€) and start logging data

Also,
Open the window peremantly in bathrooms & kitchen until you do

Any room you dry clothes in - open the window for duration

In any room you sleep in - open the window for the duration

Add heat, Keep rooms above 13/14degs

Bedroom windows open a crack, bathroom/kitchen window open more

Vote4Napoleon

For what it's worth I'd recommend you get a 6" extractor with timer, they pull so much more out of a room than a 4" fan

listermint

One . Extractor fan.

Two. Insulation in the attic just above that room make sure it's fully covered.

Three. Make sure bottom of door as enough gap for ventilation fans need negative pressure to operate. One of the serious problems with Irish apartments is terrible pressure balance with ventilation from fire doors.

listermint

Vote4Napoleon wrote: »

For what it's worth I'd recommend you get a 6" extractor with timer, they pull so much more out of a room than a 4" fan

A good 4 inch fan can pull in twice what an average 6 inch will.

Read the pull of the fan most have ratings

Calahonda52

listermint wrote: »

A good 4 inch fan can pull in twice what an average 6 inch will.

Read the pull of the fan most have ratings

The issue with the ratings is that they are lab based: smaller bore flexible ducting creates a lot of pressure losses
Also the X section on a 6" is 2.25 times that of a 4 inch: Pi r squared and all that.

OP: make sure fan has a draft baffle

odyssey06

BryanF wrote: »

Add heat, Keep rooms above 13/14degs

Just curious about this particular temperature?
What would be the difference between 5 or 10 versus 13/14 degrees for mould?

listermint

Calahonda52 wrote: »

The issue with the ratings is that they are lab based: smaller bore flexible ducting creates a lot of pressure losses
Also the X section on a 6" is 2.25 times that of a 4 inch: Pi r squared and all that.

OP: make sure fan has a draft baffle

Flexible ducting?

Why would anyone use that unless they had to.

Through the wall , Standard 4 Inch ducting and fan. There is no need for 6 inch fan or running into the attic space causing more problems.

BryanF

odyssey06 wrote: »

Just curious about this particular temperature?
What would be the difference between 5 or 10 versus 13/14 degrees for mould?

Due point in cold surfaces

adocholiday

Thanks for the input everyone. I suspected it was a case of poor ventilation but was concerned that there could be something else to consider. This weekend I'm going to:

• Clean the ceiling with a bleach solution
• Use some left over mineral wool to further insulate the space above the affected area
• Lift the carpet, the bare concrete floor will be fine. Carpet in a bathroom is disgusting anyway!
• Clean down the windows and leave them open as much as possible
• Organise someone to install an extractor fan

Anything else I should do to start? Would it be worth buying a dehumidifier also or is that just overkill?

Edit: In terms of keeping the room at 13/14 degrees we have no heating in the en-suite aside from a small wall mounted blow heater. The electric heater in the bedroom is the far side of the room and is just about enough to heat the room itself. Can't imagine it bringing the en-suite up to any sort of reasonable temperature. We're getting full central heating installed soon so I may ask the plumber about putting a heater in the en-suite too.

rocksolid

Definitely invest in an extractor fan, and not just your ordinary 4'' or 6'' that any typical electrician will install, they just dont have the extraction rate you will need...

I had the same problem in my bathroom, mould on the ceiling and walls, i put it down to showering and problem presisted even with the window left open...

I installed the below fan, roughly cost about €100 or so + installation, but well worth it...

https://www.fastlec.co.uk/16008-vortice-ca100v0d-in-line-centrifugal-plastic-fan.html

Wipe off all the excess mould and then get a good mould killer use it a few times.

Personally id recommend repainting the room and ceiling then using a good mould resistance paint.

A little tip - when you have the mould killed off, before you paint the room, paint over any mould spots with polybond first.

listermint

Big figures on that fan,

Performance: 235m3/hr (65.3 l/s) (High) , 150m3/hr (41.7 l/s) (Low)

That should suck the person out of the room too

rocksolid

listermint wrote: »

Big figures on that fan,

Performance: 235m3/hr (65.3 l/s) (High) , 150m3/hr (41.7 l/s) (Low)

That should suck the person out of the room too

Yep there is, but it works, it doesnt allow the steam to build up in he bathroom whatsoever, sucked out straight away.

Have it in about 4years now and no mould whatsoever in the bathroom since

Metric Tensor

Is it loud rocksolid?

Poll Dubh

To prevent mould you need insulation, ventilation and heating. The heating and insulation prevent water vapour from the shower from condensing on cold surfaces and ventilation removes the water vapour the room.

If you still have damp/mould issues then the plumbing or the roof is leaking.

Dehumidifiers and sprays treat the symptoms rather than the cause.