On Apr 28, 7:03*pm, (Una) wrote:
Una wrote:
Under the very old asphalt shingles on my house is 2 layers of 1/2 inch
sheet board, marked "Weyerhaeuser" "insulation sheathing board" "1B"
"R1.92" and "COMBUSTIBLE MAY SMOLDER OR BURN IF IGNITED" (and indeed it
does burn easily). *It appears to be wood fiber composition board. *It
may be 30+ years old.
Art wrote:
Celotex was a brand name that made siding and roofing stuff. *I believe they
went bankrupt long ago and someone bought their name.

Sure. *Weyerhaeuser is still in business, though. *Anyway, my questions
are along the lines of:

What is this product called? *The brand name or the general class name.
What is its R value?
Is it more flamable than what we might replace it with?
Is the product on my roof in good condition or bad condition?
Does it tend to rot? *(The roof leaks, and may have done so for years.)

It is brown, except the upper surface which is black and oily. *The
printed text on the upper surface is brown on the black and in places
still easy to read. *The board feels rather soft and crumbles easily.

The roofer proposes to strip this stuff off completely, put on a 4 inch
insulation, put a 1/2 inch plywood or OSB decking on top of that, then
felt and shingle.

* * * * Una

I didnt see the roofer proposing 4" of insulation, which is worthless
in a vented attic