I have a rather large cabin at the end of my garden.. for the fairies
Its 14m long x 4m wide and was built several years ago.

It's cladded in featheredge boards and is looking tired in places.
The boards (6"x10mmx5mm) came pressure treated and are single fixed
with 35mm galvanized clout nails.

Some of the boards have cupped on the most exposed side and pulled the
nails.

I want to give the whole thing a make over... replace boards where necessary
and refix using a longer lasting fixing, but I want to keep spend down and
not redo things which are not necessary.

I was thinking about hiring a screwgun with colated screws (my builder mate has
one he calls a gattling-gun, it's not like a plasterboard collator but I don't know it's
proper name) and adding additional screwfixings whilst leaving the current nails in where
they are still fixed.

So, in summary:
Replace badly cupped boards
Go over entire surface adding screws in addition to clout nails
Treated the whole thing once done

What would you recommend in the way of fixings, method,
treatment products etc?

Ta muchly... deano