Peeling paint, mould & way forward

16 Oct 2006
Reaction score
United Kingdom

I've had a good search around in the forums but seem to get conflicting answers.

Could anyone help with my problem?

My bathroom had mould spots on the paint (it's the coldest room in the house), and so I sugar soaped, used mould killer, and painted over with 2 coats of satin emulsion. To my horror, several weeks later after going away for a week, I came back to flaking paint around the coldest parts in the corner and by the window. I have scraped off the paint and sanded, and can still see the old mould spots there.

What do I do next before I paint? Use bleach? Mould killing paint? PVC? Or Primer?

thank you - it's fast becoming the bane of my life :mad:
Sponsored Links
Bleach mixed in hot water will kill it off but it will probably grow back in any damp areas eventually, thats the problem with bathrooms with poor air circulation ior a cold exterior wall .
Try painting with asolvent-based eggshell rather than emulsion ;)
thanks guys - unfortunately I've done all I can to cure the condensation problem (fan, opening window, heating, insulation). Short of moving out I'm not sure what else we could do :)

I'll try the bleach and eggshell thing and see how I go. The weird thing is, the old paint never flaked off even when it was mouldy?
Sponsored Links
thanks guys - unfortunately I've done all I can to cure the condensation problem (fan, opening window, heating, insulation). Short of moving out I'm not sure what else we could do :)

I'll try the bleach and eggshell thing and see how I go. The weird thing is, the old paint never flaked off even when it was mouldy?

Hi, it sounds like you need to do some work to the OUTSIDE of the wall and not the inside. Damp can only be cured from outside. Also make sure the bathroom has lots of ventilation, especially after a shower or bath or when drying clothes or towels on the radiator. :)
I don't yet know why you haven't been able to remove the warm, damp air from the room by ventilation.

Tell us how big it is, what kind of extractor fan you use, when this fan is turned on, and how long it runs after the room is vacated.

Is damp coming from leaky plumbing or roof or up from the ground or through the wall after rain?

You say it is the coldest room in the house. What is the wall, floor, celing and window construction, and how is it insulated and heated?
Right, sorry for late reply.

The room is around 3mx3mx2.5m.

The extractor fan comes on with the light (around 80 m3/hr), but we leave it on for around 30 mins after having a shower. Recently we've started opening the window.

It has a flat roof, but the problem is definitely condensation as it is dry before shower, and dry later on.

I had cavity insulation put in last year, but if anything seems to have made problem worse. There is no roof insulation as far as I know. It has a radiator which comes on every morning.

I don't dry any clothes/leave wet towels in the room.

Any ideas? thanks :)
if it is condensation relating to use of the shower, then improved ventilation should clear it. You may need a better fan. Can you describe the one you have?

for best results, when the fan is running, the window should be closed, but there should be a small gap under the bathroom door so that air can be drawn in from the house. Because water vapour is lighter than air, it should rise towards the extractor, and the air from the house should replace it. If the fan works with the light switch (plus delay) then by fitting a CFL (energy saving lamp) the cost of leaving it on for longer will be very low.

I gather the bathroom is cold. This will tend to encourage condensation on the walls and fittings. Is it an extension room with outside walls? the bathroom walls have cavity insulation, right? You say it has a flat roof so unless fairly new it is probably not well insulated. Is the window double glazed? does it get wet? Does it have a concrete floor, and does it seem cold or damp? How is the bathroom heated? Do you have a hot water cylinder, and is it in or close to the bathroom?
The fan is a Greenwood Airvac, 150mm2 with around 80m3/hr extraction rate. I often leave it for at least 30mins after the shower, often longer. There is a gap of around .5-1 inch under the door.

I did look at more powerful fans, but couldn't find one of the same size.

It's the coldest room in the house. Not sure if it has a concrete floor, but it's slate tiles, so is very cold to touch but not damp. The window is double glazed, but often gets condensation.

We have a combi-boiler, so no hot water cylinder.

any suggestions gratefully received
How is the bathroom heated?

85m³/hr is typical of a weedy 4" bathroom fan. If you have a 150mm duct, you can fit a much more powerful one such as
although this one does not have an overrun timer, it is quite cheap. Most more powerful bathroom extractors are intended for fitting in-line in a duct and are usually fitted in a loft, but as you have a flat roof you probably have insufficient room.

The higher extraction rate will be much more effective at removing water vapour. The gap under the door sounds fine (you should be able to feel air entering through the gap when the fan is running)

This one is not suited to be installed directly above a bath or shower (most are not, due to regulations relating to electrical safety and water)

verify that the fan is tightly sealed to the wall so that suction is not lost through leaks.

Insulating the roof will help keep the room warm, but with a flat roof, this will need you to strip off either the plaster from underneath (so do it next time you are decorating) or the roof cover off the top (so do it when it is being recovered)
There's just a radiator, which comes on in the morning.

The front is 150mm2 but the ducting is 100mm diameter. Is it difficult to widen the hole? It's in a wall rather than the ceiling.

thanks for your help :)
how big is the radiator?

does it seem to be hot all over? (too hot to hold?)

There should be some centrifugal fans that exhaust through a 100mm port, but I couldn't find one just now. I reckon you need an extract rate of at least 120m/hr to make much difference over your existing 85. Have a trawl through that website with the other fan, and also look at other suppliers (you could search the Xpelair or Greenwood sites, or

If you can get one it will save knocking the wall about.

Centrifugal extractors are generally quieter and more powerful than axial fans. (the element is wheel-shaped not propeller-shaped)

It is quite tedious to enlarge a hole in a wall, but it is quite easy to make a new one. You can hire a "Core Drill" from your local hire shop, and it will make a very neat round hole though a wall (one leaf at a time). Then you insert a plastic duct into the hole, and fix it at both ends with mortar. You can get the cutters in various sizes, but if you go this route, buy the duct first and take it with you so that you get a cutter that it will easily fit.

If you are making holes through a cavity wall, be careful not to let rubble fall dowm the cavity, and stuff loft insulation fibreglass into the exposed gap as any cavity insulation is likely to be disturbed.

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local

Sponsored Links