Garden shed leaking HELP!

SUPERGIRL2020

The builder has said that paint is only for roofs 

Bendy_House

Yes, but it would undoubtedly work great on the outsides of the walls too.

But I'm not going to suggest you do this. 

It would work tho'.

But you shouldn't.

But you could.

Best not.

Mutton_Geoff

I'd try and get the shed permanently moved a few inches away from that boundary fence, looks like your neighbours plants could be touching the back of your shed through the trellis. An air gap will aid ventilation and allow the outside to dry properly after being wet.

SUPERGIRL2020

This is the inside of my shed this winter - not sure what to do about it 🤷‍♀️

ThisIsWeird

Well, the dampness on the roof comes down to....the roof.
So it looks as tho' it needs another couple of coats of that roof seal. These products are effective, but require the layer it's applied to to not break. Ie, if you apply this to felt, it'll only be as good as the felt layer - if that tears or cracks, then the coating is likely to too.

Ganga

Also bear in mind that the sides are just wood and driving rain will get thru , most sheds dry out in the sunshine and as others have said if you can help by not putting the shed walls against plants etc this will help.

Lorian

Replace the felt on the roof, personally I prefer edpm rubber, costs more but you do it once and lasts a lifetime. I'd fit guttering too as the runoff from the roof is being directed at the walls. Seal the corners strips with silicon too (although they really should have been bedded in silicon beads when constructed)

ThisIsWeird

Two separate issues there, SG, just as before.
The roof covering looks to have been breached again, so I guess either the felt has cracked, or perhaps it's just the way the felt hasn't been sealed at the ends of the roof, so the rain is getting in there? 
That's a decent shed, so I'd suggest worth having a complete new roof covering put on. EDPM as Lorian suggests, or - if felt - make sure it's good thick stuff, and not the type that's usually supplied with sheds...
Also, ask the fitter to ensure the covering is fully sealed down the front and back edges - that's a common failure point, and often where rot sets in.
And then there's the water which appears to be blasted past the boarding's T&Gs. Which shed side is this? Does it face the prevailing weather?
T&G usually makes a decent job of keeping put normal rain - it's designed so that water running down the outside wall cannot get through. A few things can allow this, tho' - heavy rain is being driven forcefully straight against the wall, forcing some if it in, up and around the grooves to get through, or some of the 'tongues' are broken, so allowing the rain through (unlikely, as it's happened to a lot of boards), or perhaps the boards have been assembled upside-down! Someone must have done such a thing  to a shed at some point!
Best, I guess, since you are not a DIYer, is to get a recommendation for a fencer/handyperson type, and have the roof recovered. And ask them to determine where the wall rain is coming through - even if you need to play a hose over the side.

Nobbie1967

This is the EDPM that I fitted the other weekend on my new shed, probably about £100 for the kit for your shed. Went on really easily, you just need a period of dry weather to remove the old felt and let the wood dry out as the glue is water based. A lot less faff than wrangling heavy rolls of felt or tearing it as you attempt to nail it in place while it tries to fall down the roof.

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SUPERGIRL2020

Thanks everyone it's the left side of the shed and the roof that gets the most rain. 

Should I get some exterior waterproof wood sealer? If so which one do you recommend