Timber flooring - What To Expect

Wood floors add warmth, richness and value to any home, they stay looking great for years and often take on their own patina and character over time. As a solid surface, it will not harbour dirt, pet hairs, dust mites or moulds, ensuring a better living environment for allergy sufferers. Timber flooring is easily kept clean with the use of a damp, anti-static mop. There are numerous colours, textures and sizes to choose from, making it a very flexible material to work with.

Timber Colour
Within the timber species available there is an extremely wide range of colours - from pale Ash, to the warmer Rimu, right through to darker woods such as the brown/black Wenge. Many timber species can also be stained – ebonised to create a blackened finish or whitewashed to create a much paler finish. Dark floors can add drama and contrast, however if you decide to go very dark be aware that dirt will be more obvious. Mid-range colours are more forgiving. Light floors will generally look more contemporary.

The polyurethane and oil finishes (available in a variety of sheen levels) we apply to our solid timber floors are clear. Prefinished flooring will closely match the sample at the time of laying. However, as wood is a natural, sensitive material its colour will change over the course of time due to exposure to light sources, whether natural or artificial. The speed and degree at which this photo-chemical reaction occurs depends on the type of wood chosen and the finish applied. A slight colour change shortly after installation is usual.

Timber Species
When choosing the “look” you wish your home or office to have, it is important to consider which type of timber you would like to use. In some wood species, like Maple, the appearance of the wood grain is very subdued. In others, like Red Oak or Walnut, it is very dominant. This will determine how busy your floor will look. The colour will generally be determined by your choice of timber, however within one species there may be variations. No two trees are alike; therefore we cannot always guarantee that your floor will exactly match the flooring sample shown.

At this point you will need to make a decision between a prefinished engineered or solid wood floor. One is not necessarily better than the other. You want to find out which of the two best suits your needs by talking to one of our knowledgeable staff members. They will know the strengths and weakness of the different products, ultimately leading to a reliably installed wood floor. (See under Prefinished Engineered Wooden Floors or Solid Wood Floors for the range of timbers available).

Environmental Issues
The best way to choose sustainable timber and avoid contributing to global deforestation, is to look for “Good Wood Products” made under the guidance of the Forest Stewardship Council (FSC) or similarly verified legal wood. Our preferred suppliers all have sustainability certification. For timber to be sustainable a tree must be planted for every one that’s harvested and the forest must maintain its ecological integrity.

timberfloors-aplant on dark timber floorcouch on light timber floor

Timber Width
Also worth considering, when choosing your timber, is the effect different widths of timber will have on the style of floor. This can range from narrow 65mm boards through to the extra wide boards of 200mm. It is worth noting however that board size can influence floor stability and movement. The squarer the profile of the board, when viewed from end on, the more stable the timber will be. For example, a floor made from 85x19mm T&G boards will better withstand movement and shrinkage, than one made from 200x12mm.

boardwidth-narrow boardwidth-medium boardwidth-wide
Narrow Width Boards
Medium Width Boards
Wide Boards

Timber Endurance
A timber floor, if treated and maintained correctly, can last well over thirty years. It should be extremely hard-wearing, so for this reason there are certain timbers we do not recommend, as these will dent more easily and can be prone to cupping and shrinking - we always recommend stable hardwoods. In areas of exceptionally heavy traffic we may recommend that you use certain types of timbers over others.

Movement within your Floor
Wood is a natural material and therefore a certain amount of movement can be expected. This is due to the absorption and release of moisture which results in the swelling and shrinking of the timber. Throughout the year, we experience a range of weather patterns - cold, damp conditions create high humidity levels causing the wood to swell, whereas heating and sunlight have the reverse effect. All timber used in flooring is seasoned or kiln dried to reduce the moisture content in the wood, however the wood’s ability to absorb moisture remains. This is reduced by a polyurethane or oil finish being applied to the wood either in the factory for prefinished engineered timber or directly onto the floor, once installed, in the case of solid timber. We recommend that all concrete subfloors are moisture sealed prior to installation. In floating floors, the underlay is moisture proofed or plastic sheeting is laid. However, a small degree of expansion and contraction is to be expected in any wooden floor. 8 to 12mm expansion gaps are left between the floor and the wall to allow the timber to grow and shrink. These gaps are covered by skirting or beadings and trims. To help minimise these effects users can stabilise the environment of the building through temperature and humidity control. See Controlling Your Environment below. Please ensure that your architect is aware that you are considering a timber floor, so that the correct type of door frames are used to all outside areas.

Wear and Tear
A certain amount of wear and tear, along with some minor scratches, are to be expected over time. These can add to the character of the wooden floor and are usually considered a feature, not a defect. Prefinished engineered floors can be sanded and recoated with polyurethane 3-4 times, whilst solid timber floors can be sanded and refinished 4-5 times. Sanding and recoating floors extends their lifetime and helps eliminate the possibility of moisture seeping into high traffic areas where the polyurethane or oil finish has become worn, for example, adjacent to kitchen sinks. We can do this for you.

Heating and Timber Flooring
All forms of heating – including freestanding heaters, radiators, heat pumps, under floor heating etc. affect the temperature of the floor and need to be increased and decreased gradually – see underfloor heating for instructions on how this should be done. Insulation in concrete slabs, dehumidifiers and heat transfer kits will also impact on the temperature and humidity level of your timber floor. The floor should remain at a temperature below 24° C or 75° F, no matter what type of heating is used. If you have any queries – please do not hesitate to call us.

UV and Sunlight
All natural products are affected by the sun. Excessive amounts of strong sunlight and UV rays will have a detrimental affect on wooden floors. It will dry out the timber and cracks may appear; in addition to this it will bleach the wood and the area may become significantly lighter. This can be greatly reduced by choosing a window glass which minimises the transmission of ultra-violet light from the sun and reduces the heat gain in a room from bright sunlight (the chemical reactions which cause materials to fade are accelerated by higher temperatures). We recommend the use of UV protection glass or having UV protection films fitted to existing windows; alternatively you could consider UV blinds. This will not only protect your wooden floor, but also your furniture, fabrics and carpets too.

Controlling your Environment
Each floor is part of a building system and the performance of the floor is dependent on other elements within the building. The key element which influences the way a timber floor will react is moisture. As mentioned above, wood is hygroscopic, absorbing and releasing moisture to and from the air depending on the temperature and relative humidity of the air. This loss, gain or redistribution of moisture creates visible movement. You can expect your floor to move to some extent. You can expect fine gaps to appear from season to season, especially in rooms which experience unusual or significant changes in humidity and temperature (both from heating and sunlight).

The moisture content of timber in a building moves towards the Equilibrium Moisture Content (EMC) of that building. EMC is a function of the average temperature and relative humidity of the building. The average EMC for NZ dwellings is around 11%, however this average will differ between buildings and also seasonally. Within the same building the EMC will vary from one part to another depending on factors which affect temperature and relative humidity. This variation can be from 8% to 14%. Unless otherwise specified your floor has been prepared and installed for an expected average EMC of 11%-13%.

Your installed floor is designed to perform to its optimum at the average EMC of 11%. It should perform well within the range of 9% to 13%. However, at 9% small gaps may appear and at 13% minor peaking (cupping) may appear at the edges between boards, as the pressure causes the boards to press upward against one another. At 8% the gaps will be more significant and at 14% the floor will be more obviously under strain. In general, floating floors will react more to a high EMC than direct fix floors and moisture problems can result in cupping and/or swelling. When the EMC falls back within the 11-13% range, cupping and shrinkage should correct itself.

Bathrooms and laundries can often have higher EMC’s. In these areas the timber should be well looked after and the following steps should be taken to keep the EMC within an acceptable range i.e. under 13%.

  • Use venting kits to vent clothes dryers to the outside.
  • Prevent water leaking from washing machines, shower doors and other plumbing fixtures.
  • Do not leave puddles of water, damp towels, bathmats or clothes on the floors.
  • Use extraction fans and heaters, as well as heated towel rails.

If the house is being maintained at a comfortable temperature and relative humidity, then the EMC should not go above 13%. Moisture content above this usually indicates a problem such as inadequate ventilation, moisture egress from the subfloor or plumbing or drainage problems. We design our flooring installation systems to be as strong as possible, however sometimes other elements of the system such as the concrete substrate fail earlier than the glue or the timber. Please see Subfloors for additional information.

Where the building design creates a sudden change in EMC over a small area, small gaps may appear in the low EMC area. Examples of this are under sky lights or in front of large glass walls (where direct light focuses on the floor), in front of heaters or fireplaces, below some types of self defrosting fridges or anywhere else where spot heating causes a drop in relative humidity, bringing the moisture content below 9%.

Where subfloor heating and heatpump/air-conditioning units are installed the moisture content of the floor should still remain within the acceptable range as long as the system is well set up and maintained and the unit is controlled by the temperature of the floor, NOT the temperature of the water in the system (where this type of system is used). Ideally the timber temperature should be around 22°C (maximum 24°C). If the timber temperature is raised higher than this the relative humidity at the surface of the wood will drop, drying the timber out below 9% and leading to gaps between the boards. Insulation in concrete slabs, dehumidifiers and heat transfer kits will also impact on the temperature and humidity level of your timber floor. Please ensure your floor remains within the recommended levels. Strict criteria must be met before our guarantee covers timber flooring installed over underfloor heating.

Please be aware that there are potential problem areas within a house where the floor may be more likely to take on moisture. This may result in expansion, possibly damaging the finish – for example by the base of external doors that do not have adequate door seals; at doors to garages, which may be left open into unheated hallways; rooms on the south side of houses which are seldom used and are unheated during winter; doorways with immediate access to the house from swimming and spa pools; underneath dishwashers which accidentally drip; potentially “wet areas” such as bathrooms and laundries as previously discussed. It is important that all areas are maintained.

It is not recommended that a house be left unheated for long periods during winter, as the EMC will rise without the drying effect of the heating and venting associated with normal occupation. After a period of being unoccupied, do not suddenly heat the house. This may dry out the surface of the flooring faster than the middle and bottom of the timber, leading to differential shrinkage. This can in turn cause cracking of the polyurethane along the joints and cupping of the boards.


©Swinard Wooden Floors Limited, PO Box 7134, Christchurch 8240     T 03 329 9669     F 03 329 9660     M 027 432 4946