Chipboard or plywood for subfloor

Chipboard or plywood? Which is better?

A long lasting solid hardwood floor is heavily influenced by the quality of the sub-floor. When it comes to types of sub-floors there is a wide range but we will focus on the two most often used in modern buildings.

First lets understand how each one is manufactured:

Structural Plywood - it is made of three or more thin layers of wood bonded together with adhesive and compressed under high pressure. Each layer is oriented with its grain running perpendicular to the adjacent layer. This provides dimensional stability and improves the strength of the board. The standard dimensions are 1220mm x 2440mm or 4 ft by 8 ft. It comes in various thickness but for our comparison we will consider 18mm thick plywood.

Treated Chipboard - it is made by bonding together wood particles (chips) with an adhesive under heat and pressure to form a rigid board with a relatively smooth surface. For sub-floors we will consider 18mm thickness tongue and groove with dimensions of 600mm x 2400mm.

Installation

Chipboard is faster to install as it has tongue and groove. The boards are laid lengthwise, perpendicular, over joists and joined together. Screws are needed to fix down the new sub-floor. Since it has tongue and groove the joints which end between the joists do not need extra reinforcement thus less work. The off cut resulted at the end of the row will be used to start the new row. Also the narrower board maneuvers more easily especially in tighter places

Plywood is slower to install due to its larger dimensions. Since it has no tongue and groove it has to be cut so the joints will fall in the middle of the joists and when this is not possible additional noggins will have to be fitted under the joint.

Sub-floor strength and long term dimensional stability

Both materials provide a good strength yet the plywood being made out of continuous layers of wood is a lot sturdier when heavy items are dropped. Most of time if the impact fall between the joists over the clear chipboard this will break it.
On the long term the chipboard tends to sag due to moisture variations as well as heavy objects pressing down or even constant traffic. Once again, the plywood, due to its construction will retain its original characteristics.

Moisture resistance

For sub-floors both materials should be treated from the manufacturing process.  The chipboard will last for a shorter time than plywood in similar conditions as in the end the small chips will expand by absorbing moisture and will crumble. Instead plywood will withstand for a much longer time. Eventually the layers will separate and the board will loose the strength but will not crumble.

Noise

If installed correctly plywood will not make a noise. On the other hand chipboard is renowned for squeakiness which gets worse and worse as time passes and the floor endures more traffic. This happens even if the chipboard is glued between the joints and it is due to its sagging tendency.

Price

Up to now there is no doubt that plywood should be used to create a solid long lasting sub-floor. This comes as usually with the price disadvantage since the plywood on a square meter is often double in price than chipboard.

Our recommendation

When our projects involve reworking the timber sub-floor we will use plywood as this will preserve the quality of new wooden floor which we'll have to install over.

Sub-floors are the key aspect in delivering a successful outcome and should be assessed and treated consciously. We are prepared to take your technical questions.