WSi = Residential visual quality

for the visible living area
 

• wood type: Spruce
• slat width: max. 140 mm
• surface: planed and sanded
• Knots, discolourations and joints occasionally permissible

ISi = Industrial visibility quality

for industrial and commercial construction

• wood type: Spruce
• slat width: max. 140 mm
• surface: planed and sanded
• Knots, discolourations and joints occasionally permissible

NSi = Industrial quality

for structural solid wood construction

• wood type: Spruce/Fir, Douglas Fir, Larch
• slat width: max. 250 mm
• surface: planed
• Knots, discolourations and joints permissible