On 2/16/2020 5:34 PM, Clare Snyder wrote:
On Sun, 16 Feb 2020 14:51:49 -0500, Ed Pawlowski wrote:

On 2/16/2020 12:43 PM, micky wrote:
In alt.home.repair, on Fri, 14 Feb 2020 09:23:09 -0500, micky
wrote:


I need a new roof, or a repair of the old one.

Another question has come up.

It seems the original roof had 3/8" plywood and one roofer wants to
patch it with some sheets of 1/2" plywood, which he says is better.

The other roofer says it will leave valleys that water will collect in,
and that's bad.

I can certainly see if the thicker stuff is below the thinner stuff,
there would be a 1/8" dip, at an angle** which makes the dip a little
less, and a bit of water would sit there until it evaporated or sunk in,
but isn't the roof supposed to be waterproof?

**Roof is 2:5 I think. Prefab trusses.

Will every replacement sheet of plywood be noticeable from the street,
two stories down, because plywood is 1/8" thicker. Should they use
3/8th to patch 3/8ths?

Sure, 1/2" is better and they probably have a hundred sheets in the shop
but have no 3/8". I never would have though the 1/8 would be noticeable
once the shingles are down but I'm not an expert on it. I'd not do it
for ceramic tile though.
I'd never put ceramic tile over 3/8 - but wouldn't the thinset
compensate for 1/8"??? When I put in the ceramic in the foyer I used
Ditra with modified thinset and 1/8 inch would not even have been
visible

An extra layer of roofing felt would probably even it out.