Loft Joist - white mould - advice please

[futureechos]

I noticed the following on my loft joists recently, and I think this is a fungal rot of some type.

We've been in the house 13 years, and I think this is a recent build up.

Only changes are we rewired, added more lagging and boarded half the loft a year ago, and I didn't notice it at the time. So loft hatch was open for long periods during that time whilst we were working and I'm wondering if moisture/spores have got in.

Anyway - what needs to be done here?

Any advice greatly appreciated.

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[jeds]

Don't worry about spores. They are everywhere and will get in regardless. Your issue is condensation and you need to ventilate your roof. Either eaves vents or tile vents - whichever is easiest. Sooner the better judging from the photos. Once vented and stabilised you could treat the affected timber with a proprietary treatment but if it is well vented any fungal growth will die off anyway.

 

[futureechos]

Jeds - thanks v much.

For ease of fitting - would soffit vents also suffice?

This is going to be guesswork but how much ventialtion do I need?
House is 9m wide by 7m? so loft floor space 63m2. Are couple of tile vents or 2x4inch soffet vents going to do the job?

Obviously 'some' are better than 'none'.


Cheers for the advice - greatly appreciated.

 

[jeds]

Difficult to know exactly how much ventilation will do the job. If it was a new roof you'd need the equivalent of 10mm of free vent on opposite sides of the roof for the full length of the roof. Soffit vents are ok - you'll have to work out the equivalent? From memory they are usually 10,000mm² per vent so 10x1000 would be one every metre.

 

[Safety First]

If you want to arrest the problem before the correct ventilation is arranged you could always put a dehumidifier up there.

The silcone absorbant types are better than the older style condensing types- better= more efficient at colder temperatures.

 

[ban-all-sheds]

... we rewired ...

Did you install recessed lights in any of the upstairs rooms, particularly the bathroom?

 

[futureechos]

... we rewired ...

Did you install recessed lights in any of the upstairs rooms, particularly the bathroom?

Actually yes - about 6 months ago in the shower room.

5xLED style ceiling lights, designed for zone 1 installs

No signs of dampness around the lights form the loft side, but on the shower room side, the lights do have a lot of condensation.

I'm suspecting that's a factor...

I'm thinking of installing an extractor fan in the shower room, sounding more and more like a plan?

 

[jeds]

Just be aware that water vapour will get into your roof regardless. Unless you have a true vapour barrier you can't stop it. Lack of ventilation and the lower temperature = condensation.

 

[ban-all-sheds]

5xLED style ceiling lights,

So you cut 5 holes in the ceiling for warm, vapour laden air to get into the loft.

designed for zone 1 installs

All that means is that they are electrically safe in that location - doesn't mean that they won't let warm, vapour laden air get into the loft.

No signs of dampness around the lights form the loft side,

You won't start to get condensation until the warm, vapour laden air gets further into the loft.

I'm thinking of installing an extractor fan in the shower room, sounding more and more like a plan?

You should have one anyway, but to stop warm, vapour laden air getting into the loft you need to build, or buy and install, sealed enclosures around all of the lights. Sealed construction, cable entries sealed, the enclosure sealed to the ceiling. They'll need to be large enough to provide enough clearance around the lights (LED ones do need it), and able to take the weight of the insulation over the top of them. You'll probably need to get a bit more insulation, as it will be going up, over and then down.

 

[futureechos]

So you cut 5 holes in the ceiling for warm, vapour laden air to get into the loft.

Erm.. yes.


Ref you other points - Your logic is flawless sir - all taken on board.

..to stop warm, vapour laden air getting into the loft you need to build, or buy and install, sealed enclosures around all of the lights. Sealed construction, cable entries sealed, the enclosure sealed to the ceiling. They'll need to be large enough to provide enough clearance around the lights (LED ones do need it), and able to take the weight of the insulation over the top of them. You'll probably need to get a bit more insulation, as it will be going up, over and then down.

One question - if the lights are allowing warm moist air to pass into the loft - If I enclose the lights and seal off, then the water vapour will condense inside the enclosure over time - is this build up of water likely to be a problem?

I know I'm missing something here.

Thanks again for the advice.

 

[Blagard]

One question - if the lights are allowing warm moist air to pass into the loft - If I enclose the lights and seal off, then the water vapour will condense inside the enclosure over time - is this build up of water likely to be a problem?

I know I'm missing something here.

Indeed you are The sealed enclosures are on the warm side of the loft so they don't really present a surface any colder than your bathroom ceiling (insulating value of the plasterboard excepted). In addition the light fitting will heat the space which is also vented back into the bathroom.

It is not a problem