On Mon, 17 Feb 2020 19:16:47 -0500, micky
wrote:

In alt.home.repair, on Sun, 16 Feb 2020 17:29:10 -0500, Clare Snyder
wrote:

On Sun, 16 Feb 2020 12:43:46 -0500, 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?
Thicker above thinner won't cause an issue, but you WILL see it from
the street with 3-tab shingles. With "high def" architectural shingles
the line will virtually dissapear with the new roof installation - but
MAY telegraph through over time.
A roof is supposed to be "highly water resistant" and "weatherproof"
but don't necessarilly count on it to be "waterproof" as in being able
to hold standing water like a pail or a swimming pool.

How many sheets of plywood would it take to do the complete street
side of the roof?

15 at $65/sheet for CDX plywood. $975

Street side, that is, just for appearance?

I'd be sorely tempted to replace the whole face
with 1/2 inch. I know I'll never put 3/8" plywood - or anything other
than fir - roof decking on anything bigger than a dog-house again
after the issues Ihad on my shed roof.

What issues on the shed?.

Here it did pretty well the first 39 years.
It bowed and buckled between the rafters so much it looked like lake
superior. I put 1/2 inch fir over top - strapped and shimmed and now
it is straight again.