Shed roof leaking

I re-roofed my tea-house a few weeks ago, using the proper adhesive and a polymer non-tear 40g felt. £40 quid a roll!

One side has an un-mineralised edge and this should be positioned at the top and the underside of the sheet that goes above it glued then nailed to the lower sheet. (youngest son with adhesive on the roller).





The adhesive won't stick very well to the mineral covering.

I used the proper nails 20mm I think, that went right through the roofing ply, as they won't be seen as I've a ceiling below the roof.
Using the short nails which are 13mm, through two layers of felt won't do, as I quickly found out, as while you're banging in one nail the one next to it is getting bounced out! Well, not quite, but it it becomes less secure and could let water in. Fortunately I'd bought a pack of both sizes.