Contractors are reshingling my roof.  They started today and rain is
expected the next several days.  I asked the contractor whether there
could be water damage from the rain.  He said that he will put tar
paper down before the rain.  Is this enough to prevent water damage? 
We expect about 2 1/2 days of rain while the tar paper is down.

Hello jo23-ga,

I have a family member who works in roofing for the company Westurn
Roofing. http://www.westurn.com/ I posed your question to him. He
agreed with the commenter and your contractor that the tar paper, if
layered, should be enough to protect the roof, but if you're really
worried, he said to lay down tarp as well. Pretty much those are your
options when nature interferes.

When we re-did my roof a few years ago, we got snow that fell on the
tarpaper for a day or so (freak storm in late April) and the tarpaper
held out just fine under an inch or two of melting snow.

If this answer requires further explanation, please request
clarification before rating it, and I'll be happy to look into this
further.
Nenna-GA
Google Answers Researcher

That is what I would have done.  The tar paper is lapped, just like
the shingles will be and the rain will just run off. If you are
worried and the roof isn't to big, buy some cheap tarps.  I have heard
that homeowners insurance will pay for any damage, but I doubt that
will be an issue.

I hope this helps.

I just had my roof (fair-sized bilevel) reshingled, and had no trouble
finding a contractor who would guarantee the job would be done in one
day. And it was, although they ran out of shingles for about four feet
of ridge-cap so I covered that anyway. I'm surprised the contractors
in this thread take several days unless you live in mansions:)

Just as a comment, I carry tarps as large as 100x100 in stock at
www.tarice.com, and can generally get a tarp to you in 1-5 days,
depending on where you live.  If you need something immediate, your
best bet, of course, is one of the larger hardware stores.  But they
generally won't have 40x60 or larger in stock. This is something they
will have to special order, or else you just need to order online
yourself.  For short term roofing projects, the cheapo blue poly is
generally strong enough, for roof projects that are going to last some
time, you need to go with heavier poly, such as the silver tarps (
1000 denier ).