Common Misconceptions About Wood.
Timber is fragile
There is the preconception that timber holds no comparison in strength to stone and steel. A pretty bold statement to make but we beg to differ! Timber comes in all shapes, sizes and species and is very versatile. As well as some types of wood boasting natural strength comparable to stone and steel, it can be treated in a variety of ways to improve its capability. To maximise strength, timber can be put through a process called ‘drying’. Wood treated in this way is placed into a kiln until it reaches a moisture content of less than 28 per cent. This will ensure the timber is less likely to have distortion, staining or drying stresses, such as warping or bowing. As well as kiln drying, other options include: air drying, solar drying and dehumidifier drying each bringing their own benefits in terms drying time and overall quality of the product. The decrease in moisture will also increase the effectiveness of any preservative treatments you may want to put on. Indeed, some treatments – such as preservatives and the application of fire-retardant chemicals require timber to be treated before they can be utilised. Additionally, drying timber will reduce vulnerability to fungal decay and bugs and insects will be killed during the process. Timber can undertake various treatment to improve its strength and compare to steel/ concrete. A great example is Cross Laminated Timber (CLT) – layers of softwood glued and pressed together. Most modern structures are made in this way and CLT continues to be a popular choice because it has exceptional strength and stability and has enabled the construction of multi-storey all-timber buildings. You can see this for yourself in the video below, showing examples of large wooden structures:
- Myth #2: Timber isn’t soundproof
This assertion is often made when comparing sound insulation in timber-frame buildings to those of brick and block – but it simply isn’t true. Now, companies that specialise in framework erection are bound by certain standards of sound-insulation performance (Part E of the Building Regulations). While timber’s already pretty resistant to noise, as with strength – it can be further improved by using special gypsum plasterboard panels. As for exterior walls, a layer of warm insulation, such as mineral wool, is an excellent soundproofing material. Generally, wooden walls have good sound-absorbing characteristics, however timber floors are low in mass, which makes them prone to poor acoustic performance and can be more challenging to ensure compliance with building regulations. Basically, you can further enhance the noise resistance of a timber frame house with the right kind of windows, doors and insulation.
- Myth #3: Timber is unsuitable in harsh weather conditions
It’s a fact that timber is a natural insulator – it stores in heat in winter and keeps cool in summer – that’s why it’s been the number one building material for most of human history. The myth of timber-frame houses being cold stems from the lack of solidity between a timber frame house and a masonry (brick/block) built house. However, due to building requirements for energy efficiency, combined with new insulation materials fitted in the frames, timber can offer greater thermal effectiveness than the equivalent thickness of brick. To meet these energy-efficiency regulations, new homes have to be virtually airtight, which is far easier and cheaper to achieve in a timber-frame buildings. In regards to harsh weather, such as strong winds, timber-frame construction affords some flexibility, which makes it particularly suited to exposed locations where extreme wind forces may result in cracking. We’ve already mentioned the benefits of CLT and dried timber in terms of its strength and stability. But to further prove its assets, timber has great seismic survivability – known to even withhold earthquakes. Just one example of this is the three-storey timber structure of the Merritt building in Christchurch, New Zealand.
- Myth #4: T imber is a fire risk
Now, we all know that wood burns well – there’s no denying that – and we all remember the Great Fire of London of 1666. So with this image etched into our minds, it’s no wonder that people have pre-conceptions that a fire in a timber construction will burn it to the ground. But don’t worry – fire-proofing technology has and will continue to improve. In a government survey, the results found no evidence at all of the difference in the distribution of the size of fires between timber-framed buildings and those without special construction, such as steel and concrete. Thankfully, timber can be treated with special substances making the material incombustible and is usually treated on or before arriving on site. Making wood fire retardant typically involves the application of a chemical formula that will protect the timber. Treating fire with fire: a traditional Japanese method of burning wood both preserves and makes it fire-resistant too – the process is called ‘shou sugi ban’, or ‘burnt cedar.’ Quite simply, it involves burning wood cladding on both sides, before cooling it with water to achieve a charred effect. Here at International Timber, we work with Lonza Wood Protection to give our customers a choice of wood treatments to suit a wide range of construction projects.
- Myth #5: Timber is classified by its hardness
This myth is more forgiving: timber is broadly classified into two groups – softwoods and hardwoods. However, these terms do not relate to the relative hardness of the wood but to the type of tree from which it comes. And just to make things confusing, you can have soft hardwoods and hard softwoods. A good example of this is balsa wood which, despite being one of the softest woods of all, is technically classified as hardwood. So the classification of timber is actually based on the species it comes from, rather than its hardness or density:
- Softwoods come from coniferous trees, such as: true cedar, fir, pine and spruce.
- Hardwoods come from broadleaved trees, such as ash, mahogany, oak and walnut.