Are nails & washers leafproof?

They might. Why is the job postponed? Winter is going to be rough on a tarp protected roof. It probably would not hurt to put a dab of caulking on each nail or bolt but is the roofer a professional? Did you ask him/her?

I would question why they are waiting to reroof your house. Two homes have been reroofed in the past couple weeks in my area. Can you get another roofer out to bid on this job and do it now?

You will be very sorry you let this guy put a tarp. I had not one but two "roofers" do this to put off a new roof until spring. It was a disaster. Lots MORE leaks because of the stupid nails and screws...and of course..lots of money wasted not to mention aggravation.

I FINALLY called a REAL ROOFER...he came..geve me an outstanding price to tear off ALL plywood and some rafters..not to mention 4 layers of roofing on the flat part of my roof. He was here all day...and ...charged me...$1600 !!!!! I mean come on !!!! They did a fantastic job...and no more Rain anxiety. !! Don't put off a REAL fix..it's just not worth it.

I would be more worried about the tarp lasting... as for the original question - sure it is possible but he did it right by using plastic washers which will help seal around the nail.

Getting his license in the spring doesn't hold water. If he's getting his contractor's license in the spring, he can still do your roof without it. What you want is someone who can do it now and has been doing it for a long time. Get references!