Suitable Amount of Insulation - Mouldy Bathroom Ceiling

[veedee]

Bathroom ceiling has developed mould

So I went into the loft and noticed that every other room (except for the bathroom) had 100mm of mineral wool insulation installed.

So I laid 100mm insulation between the joists in the bathroom ceiling. No vapour barrier.

Is this enough or is it recommended that i top the bathroom area to 270, 300 etc?

The bathroom also has a powerful inline fan installed

 

[HERTS P&D]

Loft insulation should be 300mm thick.

Andy

 

[^woody^]

100mm may well be enough to lower the surface dew point, but the more the merrier with any insulation. Don't worry about a vapour barrier.

Sterilising the area would be important afterwards. Then paint the ceiling with an anti-mould (ie wipeable) paint.

Be aware of proper use of any fan - ie an overrun or trickle use, rather than just on for a few minutes whilst in the bathroom.

 

[veedee]

Loft insulation should be 300mm thick.

Andy

I understand that this is recommended in practice.

However, my worry is that insulation that thick could potentially block the ventilation coming through the eaves. This creating other issues for me.

Is it okay to reduce the insulation thickness towards the edge of the ceiling to say 100-150mm

Then top up the rest of the bathroom to 300mm?

Sterilising the area would be important afterwards. Then paint the ceiling with an anti-mould (ie wipeable) paint.

Be aware of proper use of any fan - ie an overrun or trickle use, rather than just on for a few minutes whilst in the bathroom.

Does this sounds okay?

- Apply bleach to ceiling to kill mould, then wash off

- Apply Zinsser cover stain

- Apply Zinsser perma white

Thanks for the tip regarding the inline fan. Will make sure the fan runs for at least 10 mins after lights switched off

 

[HERTS P&D]

You are not meant to block the eaves.

Andy

 

[^woody^]

However, my worry is that insulation that thick could potentially block the ventilation coming through the eaves.

Do you actually have ventilated eaves?

If so, just keep the insulation lower at wall plate.

But again, deepening you your particular house, sometimes the cold eaves can be the problem - although normally this occurs where there is a sloping ceiling at the eaves

 

[opps]

Dilute the bleach. Full fat bleach can soften the existing paint.

A cheaper option will be a decent quality waterbased eggshell. If you then find excessive water pooling on the ceiling, you will have issues with either the airflow or insulation. It might be advisable to upgrade the extractor to one with a humidistat.

Typically, the water on the ceiling will be slightly yellow, and mould can be wiped off.

 

[^woody^]

Bleach is crap. Use a proper fungicide wash which will remain in the plaster for a while

 

[scbk]

Bleach doesn't kill mould on porous surfaces.

 

[veedee]

Fungicidal wash it is then

Do you actually have ventilated eaves?

If so, just keep the insulation lower at wall plate.

But again, deepening you your particular house, sometimes the cold eaves can be the problem - although normally this occurs where there is a sloping ceiling at the eaves

I don't believe that I have ventilated eaves

I've attached an image showing the roof/eaves etc. Does this help?

The part I have labelled 'A' is white/plastic material.

It is quite floppy

House was built in the 1960s

 

[oldbutnotdead]

Can't see the image. If you do have ventilated eaves, fix some thin sheet material (felt support trays work well) under the rafter ends (make cutouts for the joists if they sit on top of the wall), you can then insulate up to your sheet material without the risk of the soft stuff popping up into the gap