This is the case of FRT plywood that needs further investigation.
FRT plywood (Fire Retardant Treated) came into use in the 80s when masonry firewalls between townhouses were replaced with a thick, fire-resistant drywall fire barrier wall. This material is intended to resist or impede the spread of a fire for a prescribed period of time, about 2 hours.
In addition to the fire barrier wall between the units, roofing was fitted with a special sheathing treated to resist the spread of a fire. The wood is treated with forms of salts intended to get the sheathing to char and not burn rapidly.
The plywood in this photo is different.
It was covered with a layer of something, and I have never seen this before.
This something was cracking and peeling in many places.
Sending a photo to a couple of home inspector friends, none had any idea what it was.
Charlie Buell asked, "Are you sure it's FRT?"
My answer - the house was built in 2000 so it would have passed fire codes then in place and the county would have approved it.
Typically fire codes require that the stamps need to be legible, but in this case the townhouse was an end unit and the one side of the attic where the FRT was located was not possible to get to, so I had to take this telephoto. I could not read any label, though I saw a couple of stamps that looked like they had information.
The Realtor asked me what to do here. All I could say was that I thought that it should be investigated by a roofer.
My recommendation: obviously this will have to be investigated further by a roofer familiar with this form of FRT. It's best to refer this circumstance along to a specialist. It surely looks odd to me!
Jay Markanich Real Estate Inspections, LLC
Based in Bristow, serving all of Northern Virginia.
Office (703) 330-6388 Cell (703) 585-7560