Hi,

If I can expand on MB's reply... there is a reason for a membrane.

Timber and concrete are affected by different things.

Concrete whilst having a level of retained moisture, expands and contracts with temperature at around the same rate as steel.

Timber on the other hand expands and contracts depending on the moisture content of everything from the humidity in the air to the moisture content in the concrete floor.

The purpose of a membrane is to prevent the ongoing moisture rising from the soil, into the concrete and then into the timber (causing the swelling of the timber).

As this additional moisture causes an imbalance between the upper and lower parts of the timber, you get cupping.

Because timber swells across the width, the wider the plank (the trend now) the greater the possible swelling.

The type of cut of the timber also affects it. Typically a quarter cut (grain is between 45 degrees to 90 degrees to the face of the timber) will move less than a flat cut or face cut (grain is between 0 to 45 degrees to face of timber) and this is reflected in the price you pay for the timber.

As timber swells in a linear manner, the solution to stabilising it is to have the grain at right angles to it in layers. This why they call it engineered timber as it has layers bonded at right angles.

In relation to your question, we often install random length boards now and not the long length older style floorboards where battens are required. Random length can't be installed over battens as the ends are unsupported.

In all of the timber floors we install, we typically level the floor with a self levelling compound, coat it with the best membrane we can and install plywood which is glued and nailed to the floor.

We acclimatise the timber (allow its moisture content to adjust to the room) then glue and nail it to the plywood.

The floor is then left for a few weeks to allow any retained moisture in the glue to settle and the floor is sanded and 'flooded' with a mixture of the polish and timber grit. This fills any small holes and minor gaps.

Cheers

Thank you so much for all the information. Very useful.

Yes, if you are direct gluing to concrete, there must be a moisture barrier applied. If it is a floating floor, a 2mm dampscreen underlay is required.

P.S. batons not required.

Thank you so much.

I had the moisture barrier with feature spotted gum flooring glued directly down. Everybody loved and commented on the flooring. We are building again and will be doing the same. There is no noise when walking on the flooring and are warm enough in winter. We lived in Melbourne. Good luck.