Active job

Exterior wooden shingles need to be secured

I have a small roof area of wooden shingles which from the outside look as though they aren't sitting flat. It could be that there were never enough nails to secure it properly initially and the sun has made them more uneven with the rain and the sun over time. I have taken some photos but its hard to get a proper view unless you are much closer to the roof area. What I am wanting is for the shingles to be sitting flat on the roof (as they should be). So I need someone who is skilled in this area of work to come and have a look and give me a free quotation as to what needs to be done. Thanks