Roof, loft, membrane advice...

digannio

I'm a fairly frequent visitor to our loft (sad I know) and am just looking for a bit of advice. The bungalow has a low pitch roof with a Marley dry ridge with integrated ventilation and Marley modern concrete tiles.

Virtually all of the white membrane visible in the loft is clean and in good condition but I noticed recently that one section of the breathable membrane has some black spots, probably about one-tenth of the entire area. It was very easy to clean off with diluted vinegar.

I should stress that there is no major condensation problem in the loft with no water droplets or evidence of damp on any of the timber or visible water on the membrane or elsewhere.

I've made sure the loft insulation doesn't butt up to the eaves to aid ventilation.

But I've now noticed that on one side of the loft membrane (the side which has an area with black spots) most of the membrane joins have been taped together whereas the other side of the loft there is no tape on the joins... and there are no black spots where it hasn't been taped together.

Should I take the tape off all these joins to aid ventilation and air flow or can this lead to flapping when the wind gets up?

I've no idea why one side of the loft has taped joins and the other side not. I've also moved stuff out of the loft (luggage, boxes etc) to aid the air flow.

Is there anything else I should look at to halt any chance of more black spots? Loft pics included, showing the tape and other areas.

plumb1_2

Yes take the tape off, it will aid ventilation. You could also put some small foam wedges in the joints. 

They do sell the wedges, but you could use small pieces of foam pipe lagging cut up.

digannio

I've got some foam pipe lagging so will have a look at using it for this. I've noticed that there is air movement where there is no tape but it's static where the tape is. I didn't know whether removing the tape could cause some issue I wasn't aware of. I just thought the tape must have been used for some beneficial purpose.

WIAWSNB

I suspect the tape was just for tidiness, or to prevent flapping as you suggest, or possibly to cut down dust from the concrete tiles being blown in. Ie, I can't think of any good reason 😜 
Or possibly the overlap is too small, and leaves an open gap. So I'd remove at least one strip and monitor it. 
I can't imagine the presence of some boxes is going to reduct ventilation to any noticeable degree, so I wouldn't bother clearing the loft.
It just doesn't appear to be a significant issue, and could be down to current cold conditions, but certainly monitor it.

digannio

I've taken the tape off and installed a few felt lap vents just to aid ventilation up there. Will check things again in a few weeks. Seems a bit random that there was tape on one side of the loft but not the other. The tape on that one side did seem to have the effect of sealing it all up a bit too tightly.

stuart45

It could be that condensation was forming on that side because it's colder, and they thought that the moisture was  coming through the gaps.

digannio

Could be because it is the coldest side of the house. But I thought most people would know not to seal up the the natural ventilation points in a loft as tight as a drum.

I got the tape off and have some ventilation inserts in place. Will see how it goes. To be honest the black spots were just towards one corner and cleaned off easily and maybe not as bad as I thought considering the tape was obviously done years and years ago. 

Chickereeeee

Maybe the tape got damp, lost adhesion, and fell off?

Having gaps between the felt sheets can allow dirt  to be blown between the tiles and into the loft. If you find things getting dirty, you will know why/how. 

Proper eave vents would be the better solution.