Level off your sub-floor for perfect timber floor installation

In ideal environments, the sub-floor or foundation will be perfectly flat and level across both planes.

Typically most sub floors or concrete slabs have dips and hollows which need to be minimised as best as possible to achieve a high end finished floor product.

These can occur through many factors such as natural warping or installation errors.

Taking the time to get an even level sub floor or slab will make the timber floor board installation easier, and the finish will be pristine.

This also cuts down on the time required for the floor sanding process during floor board installation.

So this article we look at some options for getting that level sub floor.

Grinding Flat

These days homes are constructed using concrete slabs as the floor foundation. If your foundation has been properly set by timber flooring professionals, the finish concrete will be as close to level as possible.

There will inevitably be some areas requiring grinding and or filling to level off the surface.

Most cases grinding out the hills will be sufficient.

As concrete slabs are quite thick, taking down the hills with a concrete grinding machine won’t effect the overall strength and will provide a workable solution.

Where yellow tongue boards are installed, care must be taken to have the boards laid level and even, so as to minimise the requirement for grinding or sanding hills flat.

Although grinding down concrete floors sounds simple, this requires a great level of experience and skill.

There is specialised equipment used during the process.

A walk behind heavy duty grinder with diamond blades will give you the best results for large areas.

Self Levelling Liquid

Self levelling liquid can be used in areas of concrete slabs that have dropped over time and require building back up to achieve a height level with the rest of the room or area.

Whilst timber battens can be shimmed and levelled off to get an even height, there may be times where the concrete slab in older houses require additional repairs first with the use of a high quality self levelling compound.

Where self levelling compound is used on wood, make sure to prime the wood first.

The floor will be covered with a water saturated leveller, which will cause the wood structure to swell.

Once it dries, the wood will shrink back and could cause warping or twisting.

The primer prevents the wood structure from absorbing any water.

Timber Blocks & Plywood Shims

The typical method of achieving a level floor is by using timber blocks or plywood shims underneath the timber floor battens.

The most basic method of installation is to take plywood shims and slide them underneath the battens before fixing to the concrete slab.

To get away with using this method, the concrete slab will have to be very level and only require minor height adjustment.


Timber Joists

For sub floors on timber joists, it is possible to achieve a level and even surface by jacking the floor joists and placing shims or timber blocks underneath.

Generally only required in older timber joist and bearer constructions where the floor structure has sunk over time.

Although it can be labour intensive, raising the height of the floor joists can give the best result for the overall space.

Where existing timber foundations have begun to sink over time, this may require an inspection by structural engineers to determine if there is further long term problems to consider.

So these are just some of the methods available for levelling off your sub floor structure prior to installing timber floor boards.

Spending the time in this early stage will yield the absolute best results for your finished polished timber flooring.

Now its over to you.

What methods do you think are best for your floor application?