What is this second layer behind drywall?

acerunner

So I was doing some ceiling demo and discovered there is more than just drywall hung in the ceiling. Behind the 1/2" drywall is another layer of 1/2" board. It looks like cork or compressed paper fibers.

Anyone have any idea what that is or what its for? My best guess was extra sound dampening.

It also made it very hard to cut out because the paper fibers kept clogging the saw blade.

Attached Thumbnails

 

Willie T

Looks like Homasote, maybe their 440 SoundBarrier. Yeah, I think it's made from compressed paper.

__________________
"True eloquence consists in saying all that is necessary, and only that which is."
François Duc de La Rochefoucauld
Willie T

epson

It looks like Homasote which was a product widely used in the 1940’s all the way up to the 1970’s, then when drywall started being used homasote became a thing of the past like everything else.

acerunner

so what's the best way to cut through it?

Willie T

A razor knife.

__________________
"True eloquence consists in saying all that is necessary, and only that which is."
François Duc de La Rochefoucauld
Willie T

bjbatlanta

Or a drywall "keyhole" saw.

__________________
If you can read this, thank a teacher. If you can read this in English, thank a soldier. Support our troops.