what's this on my roof?

[Two_Sheds]

Went up lotty today, dismayed to see evidence of lots of roof leaks. Shed's only 2 years old, yes I bought a lemon

It seems to be seeping, not dripping, and there are no visible holes, nor tears in the felt. The gutter's not blocked either.

I couldn't see the roof, being a short arris, so I held my video cam up high. The white patches you can see seem to correspond with the damp patches inside.

Some kind of fungus?

I won't be getting up on the roof until this rain stops, probably May

[binley100]

Did you try scratching some off ? Or is it where somethings scratched off the bitumen coating ?

[vicky]

Could it be some sort of paint the last owner tried to patch up the leaks with?
You can buy bitumen paint for felt roofs.

[Two_Sheds]

Did you try scratching some off ?

Can't reach - to get the film I was stood at full stretch on a box

Could it be some sort of paint the last owner tried to patch up the leaks with?

no previous owner

[binley100]

You need a bigger box .........or HW to pay a visit P'haps it's pigeeon poo or something thats eaten into the roofing felt?

[Florence Fennel]

I wondered about bird lime, but it seems a bit strange for it to have that effect. Hope you diagnose it soon TS.

[Jeanied]

I think the roofing felt looks a bit thin, TS. When I bought mine the roll of roofing felt came with the shed - only when the roll was undone it had all stuck together making it impossible to use. Fortunately when I took the felt back, the shop gave me a roll of much better quality stuff to replace it. Nip down to your diy shop and get something thicker and with more grit on the surface. You may need to weather-proof the door as well - clearly the rain beats in.

[HeyWayne]

Both my sheds have taken some modification to get them working properly - they just don't make 'em like they used to eh?

I'd glady pop round and give you a bunk up, but you're bladdy miles away!

Hope it's diagnosed soon - I haven't a clue what it is. I'd be tempted to scratch and sniff.

[Aberdeenplotter]

I got fed up of having to re-felt my shed and invested in some aluminium profile sheeting. Some suppliers will cut it to length for you. A bit of an outlay but well worth it.

[Aberdeenplotter]

so I held my video cam up high. The white patches

I had a look at your video. have you overlapped your felt in the correct orientation? The way it is normally done is to lay a length of felt across the slope and then lay the next length to overlap so that any moisture runs from top to bottom without any opportunity to leach sideways. I could be wrong but I got the impression that you had fixed your felt overlapping from side to side.

Apologies if I have got that wrong.

[taff]

Also, when it snowed, the snow would have piled up on the guttering and been touching underneath the felt on the overhang. The felt against the wood would have made a channel of sorts for moisture to get in, and soak the wood. If you've seen what snow and freezing temperatures do to tarmac, it's not a stretch to think that it might have had something to do with your leaks. But I'm not a DIY expert....it may be something else...

[rana]

I don't understand why roofing felt is still used for shed roofs, when a single sheet of decent quality pond liner will do the job so much better.

Alternatively clear corrugated plastic roofs are lighter, relatively inexpensive and you can see what you are doing inside.

[Two_Sheds]

have you overlapped your felt in the correct orientation?

I dunno how it's done, it came like that. I didn't put it up either, it was too heavy & tall a job for me.

when it snowed, the snow would have piled up on the guttering and been touching underneath the felt on the overhang.

Snow. I'd forgotten about the snow ... good point

a single sheet of decent quality pond liner will do the job

what a good idea: I'll look into that when I get round to fixing it all in the spring


Thanks everyone

[Aberdeenplotter]

Felt is suitable for roofing purposes not just because it is waterproof but because of its construction which makes it very suitable for fixing with nails. As a nail is hammered in, the felt compresses against the nail effectively making it self sealing. The rigidity of felt also makes it fairly easy to nail along the sides of a roof. Downside is that it does need replacing from time to time but if fixed properly it does an adequate job for not a lot of money.

[Hilary B]

I don't understand why roofing felt is still used for shed roofs, when a single sheet of decent quality pond liner will do the job so much better.

Alternatively clear corrugated plastic roofs are lighter, relatively inexpensive and you can see what you are doing inside.

Roofing felt has a semi-reflective finish to make it less vulnerable to all the effects of sunshine (when we get any). There is also the nail-control thing as mentioned by Aberdeenplotter.
Replacing the sterling board with the plastic sheets would have its advantages, but they DO get brittle after a few years. There is always Onduline, it works well over sterling board (which is what the structure looks like).