White mold in roof

sarah69696pink

We live in a Victorian end terrace and are DIY novices. 

Last year we had the loft boarded and insulation all replaced (done by recommended tradespeople). 

I’ve now noticed white mould on the roof beams. A quick online search suggests this is caused by condensation.
I’m happy to buy the products needed to clean all the beams myself. 

My worry is
a) could the work we had done be causing this? 

b) how do we stop it coming back? 

c) is this something I should be really concerned about or common in old houses? 

MikeJXE

Yes. The work could have caused it, it maybe ventilation has been reduced, has the insulation blocked the vents or been pushed to far into the eves 

sarah69696pink

Thanks for the quick reply. I can see there are still two roof vents so they are still open. Not sure if the insulation has been pushed too far into the eves as not quite sure what that would look like? The entire floor is now boarded and the insulation is below.

MikeJXE

The eves is the lowest part of the roof and thats where air gets in to ventilate, If you have boarded over the insulation have you put it on legs so the insulation can expand to it's required thickness ?

It does sound to me it's what you have done if the white mould wasn't there before.

Little point spraying it as it will come back  

sarah69696pink

We paid a company to do the boarding and the insulation.  They were recommended to us, but we hadn’t used them before. I didn’t ask about whether the boarding on went on legs as didn’t know about that. I assumed they fitted it correctly as the experts. I’ll try reaching out to them to see if they can come out and take a look. The boarding goes almost to the eves so I can’t see if they are on legs or anything. 

MikeJXE

Are you sure you know how thick the insulation was they quoted for, It's only a matter of taking a peak in the loft to see what the difference is between ceiling and loft floor, If they put in the recommended thickness 270mm the difference should be more than that. Probable 300mm or a foot. 

Regarding the boarding to the eves, unless they notched the boarding for the roof members the boarding would go right to the tiles in which case you could get your hand down and feel for an air gap. 

I doubt reaching out to them will give you the answer you want, they are not likely to admit to faults 

sarah69696pink

Thanks I’ll head up now and have a feel/ look.  Really appreciate the tips. 

MikeJXE

Incidentally the roof vents you can see (probably on the outside in the ridge) are to stop the roof overheating and not so much to draw in cool air

Air comes in via the eves and out via the vents in the ridge 

stuart45

When you insulate the roof space, it's essential to make sure that there's adequate ventilation. The better a roof space is insulated, the more chance of condensation forming.

locky123

Sounds like the loft is colder than before due to extra insulation which is probably causing the condensation on the felt and then the water is running onto the rafters. This seems a common problem with extra insulation as seen by numerous posts. I have the same condensation problem and it goes with warmer conditions and a breeze. The rafters do not appear to have deteriorated in 10 years or the metal fixings. The solution that is usually recommended is more ventilation. A modern breathable membrane to replace the impervious bitumen felt should also help but a significant expense. More cost effective are lap vents where they flt between the felt overlaps and make an open passage for more airflow. Some have used their own DIY lap vents from pipe insulation or wedges to keep the felt. Ridge and gable end vents may also help. As with all solutions there maybe drawbacks as the open passage may allow insects inside the loft. First check that you can feel a good breeze in the loft such as today and as it is boarded go to the eves with a good torch to check that there is a decent air gap at the edge. It seems controlling the condensation is trial and error as every property is different.

sarah69696pink

Been up. Looks like it’s at least 300mm higher but no gap left. The boarding is directly on the insulation. 

I wonder if this is now just us stupidly not asking for it to be done differently or poor workmanship as in they should have known to leave a gap? 

I assume to fix the issue we need someone to come out and redo it? Plus to treat the beams?