Tongue and groove joint for wainscoting - includes triangular rib inside groove to be broken by tongue when panels swell and prevent warping

摘要

The wainscoting system using tongue and grooved chestnut panels is designed so that the panels are spoilt or warped due to humidity resulting in swelling of the wood. Each groove has a triangular ridge projecting from the bottom. This ridge rests on top of the tongue which fits into the groove. When the wood expands, the triangular ridge breaks, preventing warping. A clearance is included in both joint regions to permit the expansion to take place.