Leaking shed, having issue with nails

[MoonMan2]

The felt roof on my shed was replaced by a tradesman in Xmas 2013, he said it was 'heavy duty' felt and should last for years.

These photos were taken Xmas 2017.

Closer on the left:

Alternative view on the left:

inside, left side, you can see the ingress of water.

Close view of this ingress:

Not exactly sure how the water is getting in, anyone have any ideas?

but I thought to try and hammer down the felt more since its sticking up in a few parts, so I bought these:

The trouble is, with these 20mm nails, I can't hammer the nail fully into the wooden roof. I can get about 12mm (I think). Unless of course I hammer with all my might like Thor and risk going through the roof!

Any advice; should i simply try 13mm nails or just pretend I'm Thor and get on with it with the 20mm nails?

 

[blup]

The felt tends to degrade where it is folded over the end of the gable end, plus the batten covering it can rot. Or maybe there was pre existing damp?

Blup

 

[blup]

Over time water can also get through small tears around the holes made by the clout nails.

Blup

 

[geraldthehamster]

Consider EPDM synthetic rubber membrane the next time you do that roof, rather than felt.

 

[scbk]

To be honest, it looks like fairly standard shed felt, and often the quoted life is only around 5yrs.

The better stuff is the 35/40kg rolls.

If you're not fussed about looks, I would just patch it up for now with a tin of bitumen, on any holes/cracks/nails