PROBLEM-SOLUTION: A QUESTION ABOUT THE FLOATING METHOD
By ALEX MCCARTHY
THE question above was recently posed to several manufacturers including Haro, Atkinson & Kirby, and IDS. Their responses are published below.
When adopting the floating floor installation method, the maximum surface area that can be installed in one span is 10 metres. This applies in both length and width, limiting max size area to 10m x 10m. Larger areas require mid-floor movement provisions to ensure the floor can ‘float’ unimpeded. Once an engineered hardwood floor or laminate floor exceeds 10m, its own weight/mass prevents it from being able to move freely.
Where necessary, incorporate a mid-floor expansion joint, and use a T section profile to cover the gap.
Larger area installations may be possible in some cases, and mid-floor expansion gaps may be reduced or omitted, but only when environment conditions are particularly good and long-term stability can be ensured. In these cases, the possibility of damage occurring within the floor must be accepted.
For larger installations, where mid-floor joints are aesthetically obtrusive - or in commercial installations where high foot traffic or heavy point loading is expected, a fully glued-down installation should be adopted in favour of the floating method.
Atkinson & Kirby
If installing a wood or laminate floor using the floating method, the maximum run of the flooring would be the issue, rather than the sqm area. If large runs of wood and laminate are required, then ideally break the flooring at doorways where possible or at another point, which may not be too obvious to the eye.
Mind the gap: In especially large areas, natural expansion and contraction of the flooring can cause the floor to move into a standard expansion of 10-12mm gap left by the installer. If the floor hits an immoveable vertical object such as a wall it may buckle upwards.
Why will the floor move: Hardwood and laminate floors will expand naturally with natural changes in their environment, more specifically with changes in surrounding temperature and humidity. These flooring types must be acclimatised as it is normally not known where the flooring has been stored or transported prior to installation, so acclimatisation to its new environment is crucial.
How much will the floor move: ‘Believe or not’ calculations and tables are available and will tell you, for instance, that a 125mm wide piece of Solid American Oak will expand 0.17mm when the temperature drops by 5 degrees C, and the humidity increases by 10(RH%). Times this by a room 48 boards wide = 8.16 m expansion.
However, this calculation isn’t very often used, as the site conditions are rarely controlled to that degree. Also, different species from different origins, including solid or engineered all behave differently, so there are too many variables for this to be practical.
What is suggested by most manufacturers is to leave a 10-12mm gap which will accommodate most normal installation sizes. 1mm per linear metre can be used as a rule-of-thumb.
Many common problems include installers not leaving an expansion gap or too little an expansion or laying on a damp subfloor, causing the floor to draw in moisture an expand excessively into the gap.
So, to answer the question:
Hardwood flooring: Lengths of >12m and widths of >8m should contain an expansion joint within the area at some point. The larger the area, the larger the expansion gap should be left at 100% of the perimeter of the floor.
Laminate flooring: Lengths of up to 12m can be laid without an intermediate expansion gap within the floor. If over 12m, an expansion gap of 13mm-20mm should be left at 100% of the perimeter of the floor.
The point at which you need to insert mid-floor movement joints in a wood or laminate floor can vary significantly between flooring types and can also depend on many different factors. These include the wood specie and construction of the flooring, end use environment, width of flooring, direction of install, the type of underfloor heating in place to name just a few.
The golden rule is to refer to the guidelines in the manufacturer’s instructions as these will advise a maximum unbroken run for the flooring being laid. Abiding by the manufacturer’s own instructions is imperative because this will ensure any product warranty is retained and valid. That said, product instructions can never cover all specific end use situations and factors that may cause floor movement, so a mixture of common sense and experience is required to try and identify any other factors that may influence the need for extra floor break points.
Wooden engineered flooring is relatively stable owing to its opposing directional layers of plys, however it is still made of wood so the product will naturally expand and contract during seasonal environment changes and changes in heating patterns within the home. Therefore, it’s crucial to leave an appropriate perimeter edge and integrate a movement gap facility during the installation.
Laminate HDF / MDF based floorings are again relatively stable products, and generally more so than real wood products, but even laminate flooring must have movement gaps available in them as they will expand when subjected to changing humidity environments and temperatures. The same rules apply in terms of assessing the individual installation site, complying with the manufacturer’s instructions for movement allowance, etc.
Post-installation movement issues, such as lifting and creaking of boards, are very commonly due to tension rising within a floor where an inadequate movement gap facility has been left at install and the consequences of which only become apparent when humidity levels rise and floors begin to expand and become restricted at a point, or points, around its edges.
In floor, or “in field” as its sometimes referred to, movement joints are most commonly achieved by leaving a gap between a row of boards. This gap is then covered by an appropriately sized T moulding trim with the gap either side of the T moulding central upstand being the minimum advised by the flooring manufacturer.
In many domestic installations, simply installing a moulding at the door threshold can be enough to allow sufficient expansion and negate the need for further floor joints in the room itself.
T mouldings might not be considered the most aesthetically pleasing solution but their importance in avoiding floor movement issues should not be underestimated – often however we find that it is!