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Celotex? Old roof underlayment Una 04-28-2008
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Posted by Una on April 28, 2008, 6:23 pm
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. A small patch of it is rotted and below that is
good tongue and groove board, which may or may not be the very same T&G
boards that make up the exposed rafter ceiling of the room below. I have
no idea yet if there is one or two courses of T&G, but I do know there
is electrical wiring in the ceiling so it is either sandwiched between
courses of T&G or it is lying between the T&G and this sheathing board
stuff.

The roofer says this sheathing board is not up to current building code
and should be removed. What is this sheathing board called? The roofer
calls it celotex (?) but the celotex I find on the web seems to be an
entirely different product...?

        Una


Posted by Art on April 28, 2008, 7:38 pm
Celotex was a brand name that made siding and roofing stuff. I believe they
went bankrupt long ago and someone bought their name.


> 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. A small patch of it is rotted and below that is
> good tongue and groove board, which may or may not be the very same T&G
> boards that make up the exposed rafter ceiling of the room below. I have
> no idea yet if there is one or two courses of T&G, but I do know there
> is electrical wiring in the ceiling so it is either sandwiched between
> courses of T&G or it is lying between the T&G and this sheathing board
> stuff.
>
> The roofer says this sheathing board is not up to current building code
> and should be removed. What is this sheathing board called? The roofer
> calls it celotex (?) but the celotex I find on the web seems to be an
> entirely different product...?
>
> Una
>



Posted by Una on April 28, 2008, 8:03 pm
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.

>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


Posted by dpb on April 28, 2008, 8:08 pm
Una wrote:
...

> 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.

Sounds like good plan to me -- the celotex is probably still fine except
for the places it is obviously not, but it is of marginal R value (I
don't know the numbers ottomh, but it wasn't really an insulating
product but an inexpensive sheathing product).

Consequently, what the roofer is proposing will probably save more in
heating/cooling costs in a relatively short time than the expense.

--

Posted by ransley on April 28, 2008, 8:15 pm
> Una wrote:
>
> ...
>
> > 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.
>
> Sounds like good plan to me -- the celotex is probably still fine except
> for the places it is obviously not, but it is of marginal R value (I
> don't know the numbers ottomh, but it wasn't really an insulating
> product but an inexpensive sheathing product).
>
> Consequently, what the roofer is proposing will probably save more in
> heating/cooling costs in a relatively short time than the expense.
>
> --

Unheated attics are to be insulated at the floor, unless I missed
something

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