The north side of the ADU is fire-rated as it’s within 3 feet of the property line. This means DensGlass paneling goes over the ply sheathing on the north side, the first 4 feet of the upper roof deck will be fire-resistant plywood, and the interior north wall will be covered in fire-rated gypsum rather than standard drywall.
The DensGlass is not structural; that’s the job of the underlying nailed plywood. So the panels are screwed in rather than nailed.
Irvington Cottage 