Bamboo flooring. Turning bamboo from grass into hardwood

Bamboo flooring is at the top of the range in the shops, both in terms of price and quality. I'm not talking about laminate flooring, where it is not wood but paper printed with the wood design and coated with resins. But to that parquet classified as solid wood or laminated wood. The bamboo's path from the grass category, where it is framed, to the solid wood level is long. The plant undergoes a lot of processing that brings out its beauty and makes it stronger than many other species.

What is bamboo

Bamboo, even though some species reach 25-30 m in height, is a grass and not a tree. There are thousands of species of bamboo, all belonging to the Poaceae, the grass family. Of the bamboo species, around 1500 are those that lignify their stems and can be used in construction, furniture or wood paneling.

Even though for us Europeans bamboo is a relative newcomer to the wood and construction industry, 35-40 years old, it has been used for thousands of years in areas where it commonly grows, and is considered the first building material in those areas. It grows in tropical and subtropical regions and is a common plant in Asia, Latin and South America and Australia.

Bamboo differs from trees from the microscopic level - cell arrangement, lack of annual rings and medullary rays, lack of pores - to the macroscopic level: hollow trunk inside, lack of bark, no growth in diameter at maturity. It is a very fast growing plant, reaching full height and thickness in 6-7 months. From this point on the stem begins to lignify without any further change in size. After 3-6 years the maximum lignification is reached and the bamboo can be harvested. The stem is hollow on the inside, with nodes of stem thickness visible on the outside as a stripe perpendicular to the direction of growth.

Harvesting is done by cutting stems at ground level. From the remaining root will emerge another plant that will follow the above cycle without the need for replanting. This makes bamboo a very sustainable resource.

How bamboo becomes industrialised wood used in flooring

Bamboo is used to make all kinds of industrialised products such as OSB, MDF, PALbut the most used are those considered solid wood panels. There are two main methods of obtaining these panels, by rolling and by hot pressing.

Get laminated bamboo is quite similar to the production of solid wood panels in factories across the country. Bamboo rods are harvested, selected and cut to lengths of 2.5m. They are then passed through a device that splits them into equal parts. The resulting strips are cleaned of the outer layer and inner knots, then treated with steam and hydrogen peroxide to fade and even out the colour. The result will be that recognisable golden yellow. There is also the option of charring, a method of treating bamboo at high temperature and pressure, which gives it a very pleasant caramel colour.

The treated strips are dried to 8-10% moisture content and then sanded. Adhesive is applied and they are pressed. The sheets are rectangular in section. Their joining in the press can be done on the long side of the rectangle or on the short side. In the first case, panels are obtained in which the bamboo knots are visible as a transverse line, and in the second case the appearance is similar to radial cutting of wood (where the annual rings are visible as parallel lines). Such a panel is 5 mm thick, similar to technical veneers. Several panels, laid one perpendicular to the other and glued together, form the bamboo plywood panel which is calibrated and sanded like any other wood panel.

The technology for obtaining pressed bamboo panels follows the same steps up to the treatment, drying and sanding of the bamboo strips. They are then put into presses, mixed with glue and hot-pressed with very high force so that they interlock to form the panel. A composite material with double the density and hardness of bamboo is formed. If used as a large panel, the largest thickness is 20 mm, otherwise it becomes very hard and impossible to use. When thicknesses of 30-40 mm are achieved, the panel is cut into long pieces 10-30 cm wide. Bamboo flooring is made from these strips of panel.

Properties of bamboo

Bamboo is not a very durable wood as long as it is not treated. In rod form it can be used for furniture, both indoor and outdoor, fencing and other fittings provided it is treated first.

The structure of bamboo is quite simple, consisting of long cellulose cells arranged along the growth direction, reinforced with lignin arranged perpendicular to the growth direction. The cellulose fibres are strong and stiff while the lignin is soft and crumbly. This is why the rod cracks easily along the fibre, but is difficult to break.

Because of its high starch content it is a plant loved by insects. To make it resistant, the stems are treated with boron salts immediately after cutting. Like any other wood it exchanges moisture with the environment and absorbs moisture when placed directly on the ground. It is sensitive to UV radiation and when used outdoors, it changes colour both from the sun and from the blasting effect of winds and dust in the atmosphere.

Mechanical properties are very good, with bamboo having 2.3 times the mechanical strength of many known species. Its properties are similar oak or frasin. Industrialised wood is all the more resistant as it is used to make objects subject to aggressive action: parquet, shredders, table tops, etc.

Bamboo flooring

As already mentioned, bamboo flooring is mainly made from pressed bamboo which makes it very hard and durable. Despite its very hardness it can be scratched in extreme situations (very sharp heels, animal claws), just like other hardwood species used for flooring. This is why the flooring must be protected with very hard varnish.

If the protection is factory made the floor will have maximum strength. The technologies used allow bamboo to be coated with highly resistant varnishes which harden under the action of UV lamps. They are the most resistant floor varnishes that ensure a high durability of floors.

If the bamboo planks used are not varnished, then they must be protected with a normal parquet varnish, without special tools. Due to the structure of the boards the absorption in the board is very low, therefore the surface of the flooring must be sanded beforehand to increase the absorption capacity. It is best to consult a specialist if you have such a floor. In addition, bamboo is difficult to accept colour, so it is best to use it in its original colour to avoid unpleasant surprises. If you want it finished in different colours, buy it ready finished. You'll be spared a lot of trouble.

Bamboo flooring can also be used for underfloor heating. More information on using this type of heating when you have wooden floors can be found in the March 2019 issue of Wood Magazine. How to get hold of it find out here.

Bamboo flooring will give an exotic look to your home. It can be used in any room, the way it is obtained and the qualities making it resistant to both high-traffic premises and rooms with high humidity such as bathrooms and kitchens. It's not an inexpensive floor, so it will add value to your home.

A great quality of bamboo is its sustainability. Unlike trees, which take 50-100 years to reach maturity so that their wood can be used, bamboo takes only 6 years. And a new bamboo plantation will sprout from old roots without the need for replanting. I think it's time to pay more attention to this material that can save long-exploited species and endangered forests.