Stonewood Exterior Panels were installed on pre-finished, black 22ga galvanized steel over a Momentive GE silicone membrane. The steel supports were pre-notched for flashings to prevent buildup. The substructure was attached with #12-14 X 2” Hex Head Ultra Stainless X-3 into 20 gauge steel framing. Panel fasteners were #12-14 X 1” Pancake Head Ultra Stainless X-3.
Ultra stainless is a 410 stainless with 2% molybdenum to improve corrosion resistance and reduce electrolysis. The fastener holes were a combination of small, fixed point holes (220 mils), slotted holes (220 by 320), and oversized round holes (320) to accommodate expansion. The layout varied by shape of the panel.