Timber Floors and Expansion Joints

The other day I met with the contractor who came to lay our new timber floors. During our discussions he advised me that he was also going to be installing cork expansion joints as part of the service.

What the ...."CORK - I DON'T WANT CORK STRIPS IN MY TIMBER FLOORING - IT WILL LOOK HIDEOUS!"

Well apparently it's a must have, so for anyone who is thinking about installing solid timber flooring in their home, here's the lowdown:

Timber is a natural product that responds to changes in weather conditions. Seasonal humidity and temperature changes in the air cause boards to shrink and swell at different times throughout the year therefore small gaps in the timber can occur, particularly through the drier months. Floorboards only expand and contract across the grain - not along their length and wider boards will result in larger gaps than narrower boards.

These are our existing 150mm hoop pine floorboards which, I might add, have been down for approximately 90 years

So to prevent flooring from cupping or buckling an allowance for expansion in floors is required. The BCA calls for a minimum of 10mm expansion gap, plus an intermediate gap for any floor widths over 6 metres. However where board ends abut doorways, the gap may be reduced to a neat fit with a small gap of 1mm to prevent rubbing.

Gaps at the sides of a room are usually covered by skirting boards and do not need to be filled, however intermediate gaps need to be filled with compressible material such as cork or covered with a decorative brass strip. Our flooring contractor recommended cork as it blends in well with timber, particularly with Blackbutt which is the species we chose.

(sorry in advance for the poor quality of the following photos)

Scullery door threshold

Bedroom door threshold

The cork expansion joint is installed 2mm proud of the floor surface but is removed during the sanding process. Once the floors have been sanded and the floor finish applied, it should blend in with the rest of the flooring.

The use of expansion joints is highly recommended for Brisbane (and obviously other tropical or sub-tropical parts of the country) because they allow for some expansion in the timber during periods of high humidity. Expansion joints are also a useful safeguard in the event of accidental flooding.

I'll post some photos of the floors after they have been sanded and polished - let me know what you think.