1. General. The quality of ceramic tile installations is influenced by the stability, permanence, and precision of installation of the substrate backing or base material.

2. Carpentry Requirements. Always use exterior grade plywood. Never use flakeboard, chipboard, masonite, particle board, or cement-asbetos board as underlayments for ceramic tile. These boards are dimensionally unstable over time and have little or no water resistance. For economy, plywood sheeting with two sides unfinished (rather than finished ply) is recommended. Leave the rough, knotty side exposed to enhance mechanical adhesion. Maximum joist spacing should be 16" on center with a maximum deflection of 1/360 of the span, at midpoint. The floor must be covered with two layers of wood. Over structural subflooring of 5/8" plywood or 1" x 6" tongue-and-grooved, or other structural subflooring, secure 5/8" thick exterior plywood underlayment with screws or screw-nails. Locate screws or screw-nails at 6" centers along the panel edges and at 8" centers each way throughout the panels. In all cases, the total thickness of both layers of subflooring/underlayment should be a minimum of 1-1/4". Leave a 1/4" space between underlayment sheet edges and all materials to which they abut, such as walls, drains, posts, etc. These joints are filled with seting mortar while the tiles are being installed. Adjacent edges of plywood should not be more than 1/32" above or below each other. When finished, all surfaces must be structurally sound, dry, and free of all contaminants such as sawdust, cleaning compounds, sealers, oil, dirt, etc.

3. Primer. Before application of tile, a primer may be applied to the substrate. Simply paint Super-Tiler or Super-Weld over all surfaces to be tiled. Mortar may be applied over either wet or dry primer. Priming enhances mechanical adhesion and water resistance.