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Choosing a wooden floor: why one type of wood over another?

When it comes to wood flooring, choice is hugely important. Richard Aylen takes a closer look at why this is so.

THERE are many types of wooden floors available including different plank sizes and various ways of manufacturing a floorboard. The client or designer’s final decision will be based on several factors, but I want to look specifically at the choice of timber itself. For solid hardwood floors this issue relates to the whole board, and for engineered products we’re talking about the thinner decorative layer on top.

Let’s look at some of the most popular types of timber that manufacturers are offering and compare them. Do some types offer substantially better performance or value than others, or is the choice simply based on aesthetics?

I have attempted to include the most popular types of wood that you are likely to see in manufacturers ranges but I don’t claim to have included everything because with some sources of timber becoming depleted or restricted, especially tropical woods, some manufacturers are trying to innovate by using wood species that perhaps have not traditionally been used for flooring before.

Aesthetics is a good topic to start the discussion. Each client and designer will decide generally which type of timber looks ‘right’ for their particular application.

Starting with a choice between ‘light, medium or dark’ we find lighter coloured timbers such as beech, maple, ash, hevea (rubber wood), pine and birch. Lighter shades still can be created using factory surface treatments resulting in white or grey shades and a very ‘Nordic’ look. Surface staining treatments or coloured oils are often used to achieve this. Medium and darker shades include oak, walnut, teak, and some mahogany species.

Here too factory colouring treatments can be used to create a wider choice. For customers looking for very dark floors natural wood species can be hard to find, so a stained or vacuum treated floor is often chosen. One such example is ‘fumed’ or black oak where a very dark brown/black floor is created by vacuum treating the wood with a process that penetrates most of the way through the floorboard.

Stained colours can add something more than a uniform colour change, as with certain wood species such as ash and oak a surface stain or coloured oil can really highlight the wood grain and make it visually stronger compared with the natural, unstained version.

Many clients and designers will base their choice of timber floor upon aesthetics, the floor’s colour, texture and grain patterns. This is fine as a starting point and for residential use you’ll not go far wrong with almost any of the timbers currently being offered by manufacturers. The most worthwhile discussion to be had here is in relation to the surface treatment the manufacturer provides. The quality and durability of factory finishes can vary significantly and unfortunately it’s very difficult to assess this from samples.

Natural features, grades and other choices
Some manufacturers, especially of solid hardwood floors, offer a choice of grades. Grading usually means making a floor using either plain, uniformly coloured timber or using wood with more knots and colour variation. My own company, Junckers, for example, offers a choice of three grades with many of its plank or strip floors.

There aren’t really any technical differences between grades in terms of performance, strength or longevity, but visually they can be very different. For clients who appreciate the beauty of real timber a large area of wood flooring that has prominent colour variation and knots can be visually stunning. Interior design trends are currently moving towards warmer, richer colours and more defined textures, rather than the light plain colours we have seen in recent years. For wood flooring this means floors with more knots and colour variation are coming into their own.

Availability and environmental considerations
One of the most significant changes within the hardwood floor industry in the last 20 years or so is the availability of certain types of timber and the growing requirement for everyone in the supply chain to prove they are using timber from sustainable sources. I believe that today we should be able to say with confidence that every manufacturer is supplying sustainable timber and that clients will buy nothing else, but I’m afraid we’re not quite there yet, even though almost every company you can name will claim they use sustainable products and processes.

The best way to check manufacturers’ sustainability claims is to look for certification from an independent and accredited organisation.

For wooden floors the two main sustainability schemes are FSC, the Forest Stewardship Council, and PEFC, the Programme for Evaluation of Forestry Certification. These two organisations provide a chain of custody for the timber, which is a type of audit trail, from where the tree grows in the forest to the point where the finished product is delivered to the client.

It’s a sad fact that many wood floors from some of the largest suppliers offered in the UK today have no independent certification. In terms of abundance, timbers we tend to import from Europe, the Nordic countries and the US are usually freely available, largely owing to the sustainable way forests are managed in these regions.

Timbers in this category include beech, oak, maple, and many types of softwood. Ash used to be freely available but in recent years supplies have unfortunately been depleted by ash die-back disease.

The picture is less clear when it comes to tropical timbers and other global regions such as South America, Asia and the Far East. These regions used to be abundant sources of teak, mahogany and more exotic species all prized for their appearance and durability. However, supplies have become depleted as a result of rain forest destruction and loss of other similar habitats.

This has led to some countries banning the export of certain types of timber to try to ensure preservation of their forests and natural habitats, leading to floor manufacturers switching to unusual types of wood that may be from other tropical sources, not yet restricted. You can still check their sustainability by knowing if they have full FSC or PEFC accreditation.

For engineered floorboards you need to check that any claimed accreditation relates to the whole board and not just one or two of the layers within it.

Physical characteristics and durability
If you choose one of the most freely available timbers such as beech, oak, ash or maple and you maintain it properly you will have a floor that is suitable for most types of use. In fact, the overall life span of the floor is influenced more by how many times it can be sanded.

A 22mm solid board can be sanded between eight and ten times during its life and an engineered board with a 4mm top layer will usually be good for two sandings.

If the floor is to be used for very heavy traffic, then some softer woods may be best avoided. These can include cherry, walnut, hevea and some types of pine for example.

If you broadly classify some of the types of timber discussed here, in terms of their hardness, at the top of the list you have press-dried beech and Canadian maple, followed by oak, European maple, ash and then hevea. There are many types of pine, and hardness can vary from relatively soft redwood, to pitch pine at the harder end of the scale.

There are laboratory test methods for measuring the indentation resistance of timber, namely the Brinell or Janka test methods, but converting test data into a strategy for selecting timbers for floors is far from straightforward because the floor’s surface treatment, type of use and the way it’s maintained can be just as influential over the lifespan of the floor, if not more so.

When discussing durability, we often talk about abrasion and scratch resistance, but these issues are more closely related to the surface treatment that is applied to the boards rather than the timber itself.

Manufacturers of some types of floorcovering including carpet and vinyl, will rate their products for different types of use so customers will be guided to the best choices. No such system exists for hardwood floors, and I think this may be because wooden floors are different from other flooring products in that they can be maintained with coats of lacquer or oil, or fully refurbished during their lives. In theory you can make a ‘less durable’ floor more durable by maintaining it more often, rather than replacing it.

In terms of loadbearing and strength the choice of timber becomes important when the floor is subjected to high point loads, heavy impact or high wheel loads, and especially when it’s used for activities such as sport, fitness or dance. You can achieve high levels of impact resistance by choosing timbers such as beech, maple and ash.

Oak, often considered one of the strongest timbers, isn’t as impact-resistant as those mentioned above due to its grain structure, and often a fumed beech floor such as Junckers SylvaTech will offer significantly greater impact resistance along with a similar colour to oak.

With an engineered floor the overall construction of the board has a greater influence on the board strength, rather than the decorative layer on top.

The ways of making an engineered floorboard are many and varied, and a few of the longer established manufacturers will offer technical advice. However, a large proportion of the engineered floorboards imported to the UK are from far eastern factories and many customers won’t be able to make direct contact with the manufacturer if they need specialist advice.

Sustainability is increasingly one of the most important criteria when choosing a particular species of timber for a floor and as discussed earlier, this is an area where manufacturers credentials and policies can differ widely. The only way I know to achieve any level of understanding of what you’re being offered is to look for an independent timber and forestry accreditation scheme such as FSC or PEFC.

If the manufacturer isn’t offering evidence of this up front, then it’s highly likely that despite whatever else they say, the timber they’re offering you won’t be from sustainable sources.
Richard Aylen is technical manager at Junckers UK

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