Paint Grade Fir Stair Tread – PGTREAD Call For Quote $10.19 Interior Paint Grade Fir Tread 1″ x 11-1/2″ View Product Catalog Paint Grade Fir Stair Tread - PGTREAD quantity Add to list Want a discount? Become a member. SKU: PGTREAD Categories: Exterior, Stair Parts Description Description Paint Grade Fir tread, some pin knots, for interior stair systems. PGTREAD – 1″ thick x 11-1/2″ from nose to back. Sold by the foot in random lengths.