Revisions log for question
Is fiberboard under the roof really necessary?

We are planning the following roof/first floor construction (urban villa with a hipped roof):

— Concrete ceiling instead of wood construction on the upper floor

— Insulation on the concrete ceiling

— No roof insulation.

Now our general contractor has offered us a 35mm thick fiberboard (possibly an underlayment board?).

Reason: If the shingles are damaged in a hurricane and it rains, our entire attic will not be under water.

The cost of this fiberboard is $4,000.

What do you think? Is this board necessary?

• roof
• fiberboard