The Floor Surface In Your New Bathroom

Written by bprescottJanuary 31, 2012
Bathroom floor with sink in the background

Floor Surfaces- Underlayment

Beneath any great flooring materials is a great underlayment or subfloor. The purpose of the underlayment is to create a flat, sound surface for installing the flooring material. And you’ve never had more choices for flooring material for a bathroom. From simple vinyl floor tiles to designer ceramic tiles, the floor in a bathroom is a backdrop just waiting to happen.


Hardboard underlayment is a grade of hardboard that is designed to be applied over wood or plywood subfloors or old wood floors. Never apply hardboard directly to concrete. These underlayment panels, which come in 3-feet-x-4-feet and 4-feet-x-4-feet sizes, provide a smooth base for various floor coverings. This underlayment bridges small cups, narrow gaps, and cracks in the subfloor. Fill large irregularities or low portions of the floor with a surface filler and sand high spots smooth to provide a structurally sound base. Hardboard is affected by moisture, so you should condition it by placing it in the area where you’re going to install it for at least 48 hours before installation so it can adjust to the level of humidity in the room.


Plywood is used as a subfloor and as underlayment for most types of flooring, such as carpeting, tile, and vinyl products. It is also a good choice as an underlayment over existing flooring. Plywood is a sandwich of at least three layers of wood veneer; the thicker the plywood, the more layers make up the sheet. Plywood used for underlayment must have at least one smooth side. It comes in standard 4-x-8-foot sheets and in thicknesses ranging from 1/4 inch to 3/4 inch.


This board is composed of small particles of wood bound together with resin to form a uniform board. Because particleboard is less expensive than plywood, it has replaced plywood in many applications, including underlayment. Particleboard is available in standard 4-x-8-foot sheets and in thicknesses from 1/4 inch to 3/4 inch.

Because flooring and its underlayment are subject to high humidity and moisture, most floor manufacturers don’t recommend particleboard for installation in the bathroom.


From ‘Bathroom Remodeling For Dummies’
Copyright © 2003 by Wiley Publishing, Inc., Indianapolis, Indiana
Used by arrangement with John Wiley & Sons, Inc.



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