Traduko - Sveda-Angla - När man lägger papp på taket ska pappen överlappa...

Hi again!

I would change some pieces of vocabulary here.
I think the first sentence would sound better if you use "install" instead of "put on" for the paper. Also "each paper" could be "each stip", "overlap" instead of "cover"...

Well I think you will understand better if I copy/paste the text with the corrections in bold.

When installing roof paper, each strip has to overlap the other by 10 cm. Between these layers, black glue must be applied to make the roof watertight.

Every sheet metal shall be cleaned with Målartvätt before the primer and painting.

"watertight" could also be "leakproof"

Tell me if there's something that does not convey the original.

Thank you Lilian, I'll edit.