One of the most important step before installing any floor covering is installing the floor underlayment. Poor underlayment materials and/or underlayment installation can result in questionable results, failure of the floor covering and costly repairs.

Main Steps to Installing Plywood Underlayments

• Allow the plywood to sit for several days in the room in which will be installed
• Make sure the subfloor is dry and structuraly sound
• Install and secure with 1″ deck scews a sheet of plywood, smooth side facing upward
• Make sure the underlayment sems are not aligned with the subfloor seams
• Lay the following plywood sheet – start along the longest wall and leave 1/4″ expansion gaps in between sheets and between the sheets the walls
• Secure the plywood sheet every 6″ – make sure to drive the deck screw heads bellow the surface of the plywood sheet
• Cut the plywood shets as required to follow the surface of the floor
• Apply floor patching over the screw heads and the plywood seams
• After the patching compound has dried, sand the compound
• Vaccum and wipe with a damp cloth all the resulting dust

Tools and Materials

Drilling Kit	Circular Saw
Wallboard Knife	1″ Wood Screws
Floor Patching Compond	Flooring Roller
1/8″ Notched Trowel	Jig Saw
Utility Knife	Streightedge
1/4″ Notch Trowel	Power Sander
Fiberglass-mesh Tape	1 5/8″ Galvanized Deck Screws
Thin-set Mortar	1″ Deck Screws

How Plywood is Graded?

The standard grading uses letters A, B, C & D, where A is the best quality. Typically all plywood is marked using a pair of letters – the first letter refers to one face and the second to the other.

Here are few examples of marking you may find on plywood sheets:

• A-C plywood will be very well finished on the face with a relatively rough back
• C-D plywood is great for structural use but have rough surfaces

Types of Plywood

• Interior Plywood – made for interior use only; used for wall sheathing, furniture, cabinets
• Exterior Plywood – can be used fo rinterior and exterior applications; much more resistant to moisture than interior plywoods
• Marine Plywood – to be used in high humidity applications; best adhesives are used to manufacture this type of plywood
• Structural Plywood – very strong and stable; used in applications where the apearance of the plywood face is not of a concern

Important Facts about Luan Plywood

• the general recommedation is to stay away from installing luan plywood subfloors for any project, especially for tiles
• luan plywood subfloor is made from cheap tropical forest wood
• moisure deteriorates luan plywood in significant ways
• it is not suitable for most floor coverings but can be used if moisture is not a concern