Frequently asked questions with their answers
1. What is the lifetime of PROWOOD wooden garden furniture and fence profiles?
PROWOOD wooden garden furniture and fence profiles are made of the heat-treated Finnish solid pine timber – ThermoWood®. Tests have proved that the solid timber ThermoWood® belongs to the 2nd natural durability class and is capable of 30-year lifetime. The decay resistance of this heat-treated timber is much better than that of common coniferous wood or some appropriate tropical hardwood species. High dimensional stability increases the lifetime of PROWOOD products made of ThermoWood®. Several other factors such as the frequency of subsequent surface treatment, damage control and general maintenance can help to keep products made of heat-treated wood in a very good condition.
2. Why is ThermoWood® of the outdoor garden furniture PROWOOD so durable?
The durability of the material ThermoWood® is based on the changes taking place in wood´s chemical compounds. Hemicellulose (sugar) of wood decays, therefore fungi do not have any nutrients for their nutrition. To prosper and decay wood, fungi need the right temperature (at least 5°C), the right moisture content of wood (over 20 %) and sugar. The moisture content in heat-treated wood ThermoWood® remains deep under 20 %, even if the constructions are in touch with the ground or if the relative humidity of the air is 90 %. In addition, the regular surface treatment reduces the absorption of moisture into the heat-treated wood.
In comparison to the common wood the heat treated wood ThermoWood® absorbs remarkably less moisture in the form of water steam. The hydroscopic equilibrium moisture content of the heat-treated wood ThermoWood® is 30 - 50 % lower than that of any other kind of wood, including impregnated wood. In the temperature of approximately 20°C when the relative humidity of the air is 60 - 70 %, the equilibrium moisture content of heat treated wood is about 6 - 7 %. If the relative humidity rises to 80 %, the equilibrium moisture content of the wood is still only about 8 %. This considerably reduces the movement of the material caused by moisture and any damage that results from it.
3. How does the moisture filter into the heat-treated wood ThermoWood® and how to prevent it at the exterior wooden furniture and PROWOOD fence profiles?
As well as in the case of common timber, water is also absorbed primarily through the end faces of the heat-treated wood ThermoWood®. To avoid water absorption it is recommended to treat the end faces of PROWOOD wooden garden furniture and fence profiles with a coating suitable for this wood several times. The general rule is, when a film is formed on the edge of the wood you can be sure that you have done enough treatment.
4. Is surface treatment of PROWOOD wooden garden furniture and fence profiles needed?
PROWOOD wooden garden furniture and fence profiles made of ThermoWood® material can be used outdoors without any surface treatment. However, if ThermoWood® material is not treated its lifetime is not significantly reduced but then it is not possible to guarantee all the declared properties of the material and larger than capillary cracks may appear. In the course of time the surface of PROWOOD wooden garden furniture and fence profiles gets grey and starts to crack. You can prevent the ageing process of wood by reducing the UV radiation and weather conditions exposure. Therefore, provide the PROWOOD products with surface treatment, special care should be taken of the end surfaces (end faces).
5. How can one prevent solid garden furniture and other PROWOOD products from fading?
If one wishes to preserve the natural dark-brown colour of PROWOOD exterior solid wooden garden furniture, ThermoWood® material should be treated with a suitable paint. The same treatment should be carried out at regular intervals depending on changes in the surface colour of PROWOOD solid garden furniture.
6. How often does the maintenance of PROWOOD wooden garden furniture and fence profiles have to be performed?
In case you want to keep the original dark brown colour of PROWOOD wooden garden furniture and fence profiles made of solid ThermoWood®, it is recommended to treat their surface with suitable coating including pigment and UV protection every 2 years (depending on weather and climatic conditions). In addition to keeping the appearance the follow-up treatments protect PROWOOD outdoor garden furniture and fence profiles from water and thus cracking and crumpling. Therefore it facilitates its maintenance significantly (easier removal of the surface dirt). The length of treatment intervals varies greatly depending on how much the fence profiles and PROWOOD wooden garden furniture are exposed to rain and sunlight. Regularly painted surfaces tend to last for a longer time.
7. What kind of impact does UV radiation have on the surface of PROWOOD wooden garden furniture and accessories?
The sun’s UV radiation has an incredibly strong impact on the surface not only of PROWOOD wooden garden sitting and accessories but also on the surface of all types of wood. The sun´s UV radiation causes above all the colour changes on the surface of untreated outdoor garden furniture and gradual greying depending on the degree of material insolation according to its location (outdoor garden furniture located in a shaded area changes its colour more slowly, while wooden garden furniture, exposed to direct sunshine, changes its colour faster). Weather conditions are also concerned with colour changes. The recommended surface treatment with coating suitable for wood, including pigment and UV protection, helps to reduce the harmful effects of UV radiation and increases the total lifetime of PROWOOD wooden garden sitting and fence profiles.
8. What properties of heat-treated wood (THERMOWOOD) affect the surface treatment accomplished on PROWOOD products?
Low equilibrium moisture together with slow absorption of moisture increases the dimensional stability of solid timber used for PROWOOD outdoor garden furniture and fence profiles. In addition, the heat-treated softwood ThermoWood® contains no resin. This all was removed from the wood during the heat treatment. Both these properties allow coatings to adhere better to PROWOOD products´ surface and they also increase their durability.
9. What kind of surface treatment is suitable for PROWOOD products?
For the treatment of PROWOOD wooden garden furniture and fence profiles made of solid wood ThermoWood® we recommend using paints offered by our company. In case you choose the paint yourself we recommend water-soluble pigmented oils with UV protection based on alkyd or acrylic resins. Using natural-based oils is not recommended for PROWOOD products. The correct method of surface treatment can be determined depending on the final use of the product. If a customer expects a product similar to the origin dark brown colour of ThermoWood®, it should be treated with a paint which contains a little brown pigment.
10. Why is using of natural-based oils not recommended for the treatment of PROWOOD outdoor garden furniture and fence profiles made of ThermoWood® material?
Natural-based oils contain components that were difficult separated within the production of the ThermoWood® solid wood by heat treatment and the material would be saturated with them again.
11. May coatings based on synthetic oils be used for treatment of PROWOOD wooden garden furniture and fence profiles?
Yes, synthetic oils may be used for treatment of PROWOOD wooden garden furniture and other PROWOOD products but the lifetime of the surface of the ThermoWood® material treated this way is only short-term and the maintenance has to be carried out in very short intervals or more layers of coating have to be applied at the first treatment so that the ThermoWood® material would be completely saturated. The reason is that during the thermal process and production of ThermoWood® the internal structure of wood is changed and undesirable substances are leached. The result of the heat process is the fact that the internal structure of ThermoWood® material contains more “air”. Despite the solid wood ThermoWood® which is used for production of PROWOOD exterior wooden garden furniture and fence profiles is very low absorbent, a very small molecule of oil is able to penetrate into the wood after some time. Due to the changed internal structure of heat-treated wood ThermoWood® the molecule penetrates very deep into the wood and thus the surface remains non-saturated. For this reason it is necessary to apply more layers so that the solid wood ThermoWood® would be completely saturated, which is very expensive and time-consuming. Therefore we cannot recommend synthetic oils.
12. Why is it recommended to use water-soluble pigmented oils with UV protection based on alkyd or acrylic resins as a suitable surface treatment for PROWOOD products made of ThermoWood® material?
>Only these coatings are able to saturate the surface of the heat-treated wood ThermoWood® used for the production of PROWOOD wooden garden furniture and fence profiles very well and then the wood is protected against UV radiation and climatic influences longer. The principle is very simple: into the ThermoWood® material which is very little absorbent a very small molecule of oil can penetrate after some time. This oil is the basis of these coatings. After the penetration into the wood quite a large molecule of water, which is a thinner of these coatings, slows the penetration into the depth. Then the resin, added to these coatings, makes the coating below the surface harden and then, the surface of ThermoWood® material is very well saturated after the application of usually two recommended coating layers.
13. Does the fitting used for PROWOOD garden furniture have anti-corrosive coating?
Fittings used in PROWOOD wooden garden furniture have a surface treatment that protects individual fitting components against the effects of moisture and corrosion. If this protection is not damaged, the fitting resists corrosion for all the lifetime of PROWOOD wooden garden furniture.
14. Why is it needed to glue PROWOOD wooden garden furniture when assembling it?
PROWOOD garden furniture made of solid wood ThermoWood® needs to be glued in order to increase the overall rigidity of the garden furniture, to increase its stability and also the joins would be protected enough in humid outdoor areas and the garden furniture would hold up in hard outdoor conditions. Moreover, after the gluing the pin connections don´t loosen easily and the garden furniture does not disassemble unexpectedly and thus no injuries can happen. Only with careful gluing all the positive properties of our PROWOOD outdoor wooden garden furniture can be disposed of.
15. What kind of adhesive is used for gluing PROWOOD garden furniture, suitable for exteriors?
For gluing pin connections of PROWOOD outdoor wooden garden furniture polyurethane adhesive is used that is suitable for humid outdoor areas and does not slack. This adhesive reduces noise and vibration, foams easily and fills inequalities. It is not aggressive to the surface it is resistant to common chemicals and climatic influences.
16. What to do with PROWOOD wooden garden furniture in the winter time?
At the time of off-season we recommend to protect PROWOOD wooden garden furniture by non-transparent foil or to keep it in places where the furniture will be protected from bad weather conditions.
17. Is PROWOOD wooden garden furniture harmless?
During the manufacturing process of ThermoWood® material no chemical ingredients are used. The heat treatment works only on the basis of energy and water steam. During the production of PROWOOD garden furniture and fence profiles an environmentally friendly technology, having no impact on the environment, is used.
18. Is PROWOOD wooden garden furniture ecological?
The entire manufacturing of the ThermoWood® material and PROWOOD garden furniture and fence profiles is completely environmentally friendly and does not have any impact on the environment. At the end of its lifetime the solid wood ThermoWood® can be put into alternative use or disposed of the same way as common wood is.
The heat-treated wood ThermoWood® has properties comparable to some of tropical woods, so it can be used where tropical trees would be used.
19. Is the smell of the ThermoWood® material harmful?
Tests have proved that the ThermoWood® material used as feedstock for the production of PROWOOD wooden garden furniture and fence profiles does not emit any harmful substances or odours.
20. Does the smell of the ThermoWood® material disappear in its lifetime?
If the surface of the ThermoWood® solid timber is treated with a coating, the smell disappears and does not come back. If, on the other hand, the product is used without surface treatment, the smell disappears anyway and it cannot be perceived unless one smells the wood from a very close distance.
21. Is the solid wood ThermoWood® affected by wood-destroying insect?
Tests have proved that the solid wood ThermoWood® is resistant to beetles (woodworm - Anobium punctatum, powder-post beetle - Lyctus Bruneus, longhorn beetles tribe). The test results indicate that the ThermoWood® material is also able to resist the attack of termites.
22. Is the heat-treated wood ThermoWood® affected by wood-destroying fungi?
The test results have shown a remarkable ability of the heat-treated wood ThermoWood® to be resistant to brown rot decay. The heat-treated wood has shown good resistance to fungi (Poria Placentia, Coniophora puteana) after the treatment by the temperature higher than 210°C. The heat-treated wood used in exterior requires heat treatment at higher temperatures (for PROWOOD garden furniture the wood is treated at 212°C) to reach the maximum resistance to wood-destroying fungi.
The test of biological resistance according to the EN 113 disclosed a very good resistance depending on the temperature and the time of treatment. At the used input material for the production of PROWOOD wooden garden furniture and fence profiles, the 2nd natural durability class is achieved which is documented by the KOMO certificate by the Dutch SKH company (see Certificates).
