Coating Types Timber Floor Finishes
Timber floor finishes can be grouped into four main categories. Penetrating oils and waxes, curing oils and alkyds, oil modified urethanes, and polyurethane’s, the latter three categories being available in solvent borne and waterborne. Performance parameters such as durability or resistance to wear can vary significantly within a category as well as between categories. All categories can be recoated with refurbishment coats.
Penetrating Oils and Waxes
These are blends of natural oils and waxes which penetrate the timber surface to provide a rich colour, enhancing the timber grain and natural characteristics. It is the natural subdued look of the coated timber that is often the basis of selection and these finishes are generally recognised as the traditional or natural finishes. Curing in cold weather is slow and this may require consideration. Regular application of metalised acrylic polishes are used as part of the maintenance requirements to prolong an attractive appearance that darkens with age. Hard waxes differ in that they not only penetrate but also leave a hard film of wax on the surface, thereby reducing maintenance requirements. Currently these types of finish do not form a large part of the floor finish market.
Curing Oils and Alkyds Curing oils such as ‘Tung’ or ‘linseed’ are usually selected because of their lower cost and ability to produce a rich timber colour. Gloss levels vary from high gloss to satin and they are not prone to edge bonding. Similar to penetrating oils these finishes are slow curing in cold weather, will darken with age and metalised acrylic polishes are a necessary part of ongoing maintenance activities. Alkyds are produced from reacting curing oils with a synthetic resin and this results in improved durability and reduced maintenance activities. Curing oils and alkyds are also not as frequently used as those outlined below.
Oil Modified Urethanes (UMO’s)
These spirit based solvent borne coatings combine an oil with a smaller amount of a urethane. The higher the urethane proportion, the less the oil properties such as flexibility but the higher the durability. Gloss levels vary from high gloss to satin and in recent times higher cost waterborne UMO’s providing lower emissions have appeared on the market. All UMO’s darken with age and their slow curing in cold weather needs to be considered. These mid range cost coatings are often selected as they are of intermediate durability, are not prone to edge bonding and are isocyanate free. As such they hold a moderate share of the market.
Polyurethane – Solvent borne
This coating type in the 1 pack moisture cure and 2 pack varieties provide the highest durability and film build of all coating types as well as the highest gloss levels. Gloss levels range from ultra high gloss to matt and some darken less with age. However, there is a strong solvent smell on application and due to the 5 isocyanates present additional precautions are necessary until the coating has cured. These intermediate cost coatings are often selected as they provide the best durability resulting in low maintenance, can provide a very high gloss and generally provide trouble free application. Care is however necessary regarding their edge bonding potential which can cause irregular gapping or split boards in floors. Currently, this type of finish is commonly used in Australia.
Polyurethane – Waterborne
This has the widest selection of sub-categories resulting in a spread of properties with durability from poor to arguably as good as solvent borne polyurethane. Greater care is therefore necessary in selection noting that those without acrylic provide higher durability. They are available in one and two pack options provide a finish from matt through to gloss and generally darken little with age. These coatings are often selected due to the absence of any strong solvent smells on application and because they are not prone to edge bonding. Product cost is however high and they can provide a lighter timber appearance depending on the sealer and coating used. Rapid shrinkage can also result in light coloured lines at board joints. These finishes have developed significantly over recent years and as such their market share is moderate and increasing.
Supplied by Australian Timber Flooring Association