There are many different forms of homeowners insurance, and many
different ways of covering roofs. The simplest for the homeowner is
also the most expensive -- cover all roof repairs at replacement cost.

But some policies cover only the depreciated value of the old roof, even
on a policy that otherwise pays replacement cost for home repairs. The
company doesn't want to pay for routine re-roofing as an insurance
claim.

Some policies pay only to repair or replace to original condition, and
either limit or exclude the cost of complying with stricter codes.
(That's not limited to roofs, it applies to any repair to the home, e.g.
if you have a small fire in the kitchen but the city makes you upgrade
the wiring as a condition of the repair permit, you could be on the hook
for the cost of the upgrades.)

I would strongly suggest the OP read his policy carefully to see what it
covers on his roof, what it excludes, what valuation methods it uses,
etc. If it isn't clear, an initial consultation with an attorney is
often free and well worth the price ;-)

--
is Joshua Putnam
http://www.phred.org/~josh/
Braze your own bicycle frames. See
http://www.phred.org/~josh/build/build.html