DURABILITY, SUSTAINABILITY, PROTECTION
FOR THOSE WHO WANT TO KNOW IN DETAIL ABOUT THE DURABILITY OF WOOD.
Durability
Sustainability
DNA technology
What is heartwood
Wood protection
Wood seasoning
When most people hear the word “durability” about wood, they immediately think of its ability to withstand dents and scrapes. However, in this context, it specifically refers to a wood’s ability to resist elemental and natural forces of decay. (The former notion of durability equating to physical toughness would be better explored through Janka hardness and Modulus of Rupture values.)
Degradation of wood can occur from fungus (caused by cycles of rain/moisture), or from termites or other boring/destructive insects. An overall chart defining the terms used to describe a wood’s durability in direct ground contact is shown below:
Classification
Very durable
Durable
Non-durable
Perishable
Service life (in years)
50+
30-50
5-10
less than 5
Wood species
Bangkirai (*), Merbau
Camphor, Kempas
Coconut wood
We do not use
(*) Bangkirai heartwood or a mix of heartwood and sapwood, the latter including our special in-house developed protection system is not susceptible to termites. Well maintained, the wood will last 180+ years
One of the most frequently asked questions we get is what is the life expectancy of a timber frame home from prefabricated elements?
The classic timber frame homes have lived whole centuries (refer to Japan). The current quality timber frame houses and the prefab houses as their successors are based on the advantages and durability of a range of materials, so the house as a system can function safely for a long period
Research conducted by the University of Leipzig in 2002 shows that traditionally built houses from brick are no better regarding durability and life expectancy than timber frame homes. According to the research for the last 40 years, the characteristics and elements of timber prefab houses have significantly improved and they are good to inhabit for at least 80 years - depending on the maintenance performed by their owners. Their technical life with normal maintenance can be over 100 years.
In addition to the length of time the wood can physically maintain its structural integrity, there’s also the matter of a wood’s weathering characteristics. Weathering can’t be as clearly expressed in a single number or measurement, but overall, woods with good weathering characteristics exhibit limited photo-degradation (caused by UV rays in sunlight), as well as above-average resistance to contraction and expansion, warping, and surface-checking due to seasonal changes in temperature and humidity.
Because of this vague definition, only woods that have notably good weathering characteristics are used by us. Bangkirai and Merbau are noted for both their excellent durability and their superb weathering characteristics.
FSC CERTIFIED TIMBER, ..............OR IS IT?
The Forest Stewardship Council (FSC) is an international network designed to promote responsible management of the world’s forests. It was established in the mid-1990s. Worldwide, more than 88 million hectares of forest in 76 countries are certified according to FSC standards and over 5000 companies have an FSC Chain of Custody certification.
Why undertake a Chain of Custody Certification?
In many parts of the world such as the EU and the USA the Chain of Custody (COC) certification is becoming an industrial standard for companies buying and selling timber, furniture, panel, and paper products to demonstrate that they source their products with responsibility. Over 50% of timber brought into the EU is now legal and responsibly sourced. The demand for certified timber is increasing as more and more central and local government and private development projects insist on it.
Companies that complete the Chain of Custody Certification are seen to be environmentally focused and to have proved they run a responsible business. Having completed the requirements of the Chain of Custody, they will be allowed to use the FSC logos on their products and stationery, which will add credibility to their company.
However,........
Why should a company have an FSC Chain of Custody certification in place if the timber itself is not FSC-certified up to the final shackle of the chain? In other words, why should a wooden house supplier, like us, pay thousands of dollars per, year for an FSC Chain of Custody certification when none of the timber felling concessions supplying the wood used in wooden house prefabrication is FSC certified? Certification seems to be a waste of money and only to the advantage of the accreditation body which "takes care" of all the paperwork, like in the 80s with the ISO Certification. As long as the timber at the felling sources is not FSC certified, and Chain of Custody certification for that particular wood species can be considered useless and does not have any meaning.
To back our statement above we sent an e-mail to the FSC organization. This is their answer: "If the timber isn’t certified, no FSC claims may be made concerning products deriving from it, whether or not a certification is in place".
We kindly inform the visitor that so far only a few wood species in Indonesia have been FSC certified, such as Sulawesi Teak, Java Teak, Mahogany, and a few more (non-structural timbers). These wood species are mainly used for cabinetry and furniture, but NOT ANY of the species that are generally used for the fabrication of prefab houses are FSC certified, timbers such as Bangkirai (except some flooring), Merbau, Ironwood, Nyatoh, Kempas, etc. We blame the activities of some wooden house manufacturers who flatly claim that their houses are built from FSC-certified wood. This is potentially very misleading and it undermines the FSC system, which is designed to give you, as a consumer, the confidence that you’re buying a responsibly sourced product.
Now we wonder what is closer to the truth.......Having the FSC logo used on wood products and company letterheads for wood species that are not at all FSC certified or, - as what we do -, use timber which is obtained from legal timber felling concessions, overlooked by the Indonesian Ministry of Forestry as to guarantee the compliance of the timber felling concession with the Ministry's reforestation program and comply with the v-legal system.
Nonetheless, we will forthwith join the FSC club at the very moment that timber felling concessions for either Bangkirai, Merbau, Ironwood, Kempas, or Nyatoh and others have been certified by the Forest Stewardship Council.
A new verification system is newly available to trace any piece of wood back to its origin. This will become the world's most secure chain of custody system. Each timber batch is audited from the forest to the end user by sophisticated tracking technologies. This will imply that a customer will have the guarantee that the wood used in the product that he bought (say a wooden prefab house) will be genuine and not a replacement or resembling wood.
DEFINITION OF HEARTWOOD: The older harder nonliving central wood of trees that is usually darker, denser, less permeable, and more durable than the surrounding sapwood. It is the dead, central wood of trees. Its cells usually contain tannins or other substances that make it dark and sometimes fragrant. Heartwood is mechanically strong, resistant to decay, and less easily, or not at all, penetrated by wood-preservative chemicals than other types of wood. One or more layers of living and functional sapwood cells are periodically converted to heartwood.
Sapwood is the living, outermost portion of a wood stem or branch, while heartwood is the dead, inner wood, which often comprises the majority of a stem’s cross-section. You can usually distinguish sapwood from heartwood by its lighter color.
However, color in wood can be very misleading; not all heartwood is dark, and not all dark-colored wood is heartwood. And, the relative amounts of sapwood and heartwood in any stem can vary greatly among individual species, and growing conditions. So, for a more accurate – and less specious – distinction, a more complete understanding is needed of what wood is and how both sapwood and heartwood form.
The outer, lighter-colored wood is sapwood. This is the "working" part of the tree, as water and sap will flow through the sapwood much like blood through your arteries, veins, and capillaries. While this part of the trunk is vital to the tree when it is living, it doesn't make for a very good stock for woodworking. Sapwood contains a lot of moisture, will shrink considerably when dried, and is much more susceptible to termites, bugs, and fungi.
The inner, darker section of the trunk is the heartwood. Heartwood is formed from old, "retired" sapwood, and becomes the strong spine of the tree. Heartwood is preferred by woodworking companies, as it is far less susceptible to decay and fungus and doesn't contain nearly as much moisture as sapwood, which means it will shrink less when dried. In addition, the heartwood of many wood species is termite resistant such as Bangkirai which we use for our elements which could be attacked by termites.
Typically there is less sapwood than heartwood in any given stem. The exception, of course, is in young trees and the youngest portions of stems and branches on older trees which – because they are young – are naturally dominated by sapwood. The proportion of heartwood to sapwood in the main stem does vary with species. In general, more vigorously growing trees tend to have wider bands of sapwood.
The sapwood-heartwood distinction has important implications for woodworking companies beyond the obvious implications of color. In general, only an expert can properly indicate the difference between sapwood and heartwood. The non-expert may apply some simple rules: Heartwood in general has a darker color, the growth rings are closer together and the radii of these rings are smaller.
Timber is an extremely versatile construction material that has been used for thousands of years, however, wood easily degrades without sufficient preservation. There are several different chemical preservatives and processes that can extend the life of wood. These treatments generally increase the durability and resistance from being destroyed by insects or fungi.
Firstly it is important to understand that the wood will not rot if it stays dry (less than 20% moisture content). When used outside this is not always possible so treatments can be introduced to certain timber species.
When using timber for external applications it is important to understand that timber is a variable material; different species have different properties. Some timbers, typically many hardwoods, are naturally durable and resistant to decay. Due to their density, treatments are not always required or can be maintained with longer intervals.
A wood structure will not last long if it is not properly protected against environmental conditions and pests. While several hardwoods have their natural protection in the form of tannins bound in cells, the density of the wood, hardness, and other natural protective measures, give all hardwoods a significantly longer lifetime compared to softwood, it is a good practice to be treated, and maintained to extend the lifetime and protect it from exterior factors not dealt with. In addition the moisture content, - called MC -, before the wood is worked, cut, and planned is of crucial importance for its lifetime. These protective measures are coating, kiln drying, and anti-termite measures. We have a special web page that discusses our coating system. You may log on to < coating system >
WOOD AGING VERSUS KILN DRYING
Aging wood can be categorized into 2 different procedures; No.1: aging wood using changing its natural color into an old look, and No. 2: Drying the wood to a low moisture content to avoid cracks and warping. We will discuss procedure no. 2.
To provide the finest, furniture-grade home quality, Prefabworld Bali International © has researched countless finishing processes used not only in hardwood and log home construction, but also in the fabrication of furniture, wood art, and fine musical instruments. A key element common to the finest wood products is the seasoning or aging of the wood after it is milled into dimensional lumber.
For many years we falsely believed that the gold standard for wood processing was Kiln Drying. We are not saying that kiln drying is always inappropriate since we fully agree that some furniture applications require lumber with very low moisture content that cannot be achieved with natural air drying, aging, and seasoning. Kiln drying is therefore a quite appropriate treatment for many wood species. < kiln drying > (featured article)
B. OPEN-AIR DRYING
Based on research performed by Akzo Nobel’s Sikkens © coating division, we have learned that kiln drying of some species such as Bangkirai prolongs the extraction of tannins and other extractives that if left in the wood will ultimately fail any finishing method. All hardwoods should therefore be left uncoated for as long as possible, and be air-dried in the open until all extractives have leached from the timber fibers and the timber is thoroughly dry (*). For oily resinous timbers such as Merbau a minimum of 3 months is recommended. For very dense, slow-drying timbers such as Bangkirai a minimum of 6 months is necessary. During this seasoning period, we must regularly clean all wood surfaces to remove the extractive materials that leach from the wood as it seasons such as tannins, as well as ensure that the moisture content stabilizes and adjusts to the surrounding climatic conditions. The method for regular cleaning is critical and if not done properly or carefully can damage the wood and affect its termite resistance. It is therefore not an advantage at all to assemble a wooden prefab house under cover since weathering will be prevented (no sun, no rain) and thus the proper drying of the wood is at stake (*).
In conclusion: Prefabrication carried out in the open has major advantages concerning the holding and lifetime of the applied coating.
(*) Source: Akzo Nobel Sikkens, Australia
The requirement for proper seasoning is independent of the type of finishing.
Since the many islands in the Caribbean and the Pacific and Bali share similar climates, the resulting moisture content internal to the wood will be very close to the equilibrium moisture content that would be achieved and required for homes destined for those areas.
Please note that kiln drying does not remove extractives from the timber fibers and generally dries the wood beyond equilibrium conditions. Exposing kiln-dried hardwood to tropical climates causes the extractives to begin leaching (but at a much slower pace) and the wood slowly increases its moisture content.
This leaching will cause flaking and failure of any coating system applied to the wood (water-based paints, oil-based paints, oils, etc.) and the absorption of water will cause the lumber to distort. The reason that kiln drying slows the leaching process is that the internal moisture of the lumber is a major mechanism in transporting the extractives to the surface of the wood where they can be removed.
The weathering that occurs during the seasoning process has several aesthetic effects:
♠ The color and grain contrast deepens. This is quite desirable,
♠ Some very small surface cracks will result. These are removed during step 6 of our seasoning process discussed below,
♠ Some graying of the exterior surfaces will result. This is fully removed during sanding (step 6 of our seasoning process discussed below) but does not affect it.
The commercial lumber industry could not possibly store and process enough wood to properly season it. Kiln drying is a more rapid method by which they can deliver a useful (though far from ideal) product.
When Bangkirai is not properly seasoned, the near-term consequences on the finish are shown in the picture below which is a photograph of a one-year-old gazebo post (not built by us). 
Seasoning wood for use in our homes is a multi-step process.
1) The timber is harvested using only sustainable forest practices and is sent to a mill where it is cut into the various required sizes. The time from milling to delivery ranges from 1 to 2 months.
2) Our factory receives the wood and immediately performs our proprietary process cleaning to remove the extractives that have already migrated to the surface.
3) Seasoning continues at our factory during the hot season when rain is rare. Stacked lumber is rotated to maximize exposure to the heat of the sun and accelerate the seasoning process.
4) The lumber is used to construct your home before it is fully seasoned. For this reason, we fabricate many homes simultaneously and do so in the open where the lumber is exposed to the sun and elements. This exposure more thoroughly exposes all surfaces. The fabrication time is intentionally extended as necessary to ensure that the extractives are thoroughly removed before any finishing.
5) Any boards exhibiting cupping or distortion are straightened or replaced. Straightening requires us to dismantle the boards, turn them, recondition the lumber, fix them tightly back to the support beams (or clamp them), and allow the boards to return to equilibrium stress conditions. In the vast majority of cases, the boards return to their original straight shape. If further cupping occurs, we repeat the process or replace the board.
6) All surfaces to be finished are rough and finish sanded, after assembly to remove the final traces of extractives and prepare the wood to receive the final finishing process.
The above process is both time-consuming and expensive. However, without taking these steps we cannot provide the quality product our reputation demands and our customers deserve.