Sawn Timber: What is it and What is it Used For

The vast majority of sawn timber will be cut into boards before being finished for a range of purposes. In this guide to sawn timber from Building Materials Nationwide, we’ll explain the different ways a felled tree can be cut into timber boards, and explore the range of sawn timber boards available, from carcassing timber to rough sawn timber to treated sawn timber.

The Methods of Sawing Timber

There are two main methods of sawing timber, which will both be completed at a sawmill. The first is plain-sawn timber, sometimes called flat-sawn. This method will involve sawing consistent vertical cuts along a felled tree. The timber can then be cut into equal boards that will have waves across them, showing the growth rings of the tree. This is the most commonly sold timber.

The alternative is quarter-sawn timber, which will involve cutting the felled tree into four quarters and cutting flat boards from the edge of the tree towards the centre of each. This can produce some more striking visual features and is potentially superior for furniture or visible wood.

What Shapes is Timber Sawn Into?

Timber is traditionally sold as boards of varying sizes. These can be small enough to be used for detailed work, or large enough to be used as part of a building’s frame. There are larger cuts, such as those used for sleepers, but the rectangular shape remains the standard throughout the industry.

Rough Sawn Timber

Rough-sawn timber is a timber board that has been cut to size with a circular saw. It will be of the specified dimensions but will have a rough finish compared to planed timber. Rough-sawn will come at a lower price tag than planed and can be used for structural work, or indeed for any woodwork that will not be visible.

Green or Kiln-Dried

When buying rough-sawn timber you will have the option of buying green or kiln-dried beams. Green timber is timber that has been recently cut and hasn’t been dried. Timber will naturally have a high level of moisture and is usually dried to offer a firmer build quality and a consistent size. Green timber will naturally shrink over time as it dries. There are uses for green timber, mainly due to the natural flexibility it possesses. This flexibility allows it to be shaped easily, and it is commonly used while building delicate wooden objects or curved wooden tools. Within buildings, kiln-dried timber will be preferable, as it won’t shrink as considerably over time.

Treated Sawn Timber

Alongside the drying process, sawn timber can be treated with preservatives. These preservatives will be inserted into the wood using a vacuum cylinder. Sawn treated timber can serve three purposes, but is most commonly used to resist moisture and insects. Dried timber, when used within outdoor spaces or areas with a high risk of moisture, can quickly decay. A high level of treatment (Use Class 4) will allow treated timber to be in direct contact with water or soil. Insects can easily burrow into non-treated timber, causing damage over time and damaging its look. Treated timber will also resist insect ingress, allowing the wood to be used in areas with a high insect population. The third use is to make fire-resistant timber, with the treatment ensuring that the beams will resist flames for longer. This can be valuable for fire safety within wooden buildings. 

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Planed Sawn Timber

Planed timber will have been planed (sanded) on one or more sides. This will be a necessity within any building project where the timber will be visible, as it will give a smooth and attractive appearance. It will also be needed within any furniture to avoid splinters. Planed sawn timber can be sold with one larger edge planed (planed single edge), both larger edges planed (PBS), or all sides planed (PAR or PSE). Depending on how many faces of the timber will be visible within the finished construction, you can save money by opting for timber that is not fully planed. CLS timber is another type of planed timber, with smooth rounded corners on each side.

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Sawn Carcassing Timber

Sawn carcassing timber is designed for use within the framing of a building. It will be certified as load-bearing. As it does not need to be seen, carcassing timber does not need to be planed. It will be strength graded, usually to C16 or C24 level, with slow-growing C24 reflecting a greater level of strength. Carcassing timber will normally be both kiln-dried and pressure-treated, to ensure consistent long-term performance. 

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Our Range of Sawn Timber

Building Materials Nationwide sells a huge range of sawn timber products, suitable for use in both large-scale construction projects and personal DIY work. We stock CLS timber, timber that has been planed on all sides, structural timber, and treated timber. All of these come in a variety of sizes and can be delivered in bulk across the UK. We also offer trade accounts for customers within the building industry. Our trade account holders will gain access to our full range of building supplies, our speedy delivery services, and the services of their own dedicated account manager. Sign up for a trade account through our website today.

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