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Timber guide

Jewson guide to timber

Guide to timber: Types, grading & sustainability

At Jewson, we pride ourselves on our wealth of knowledge and expertise when it comes to timber. In fact, it's how we started 185 years ago as a timber merchant. Our extensive range is of the highest quality. We stock both C16 and C24 Structural graded carcassing timber, high grade Redwood and Whitewood machined timbers, all with chain of custody certificates from both FSC ® and PEFC ™ and more.

Our range of sheet materials is extensive, we provide structural and joinery quality hardwood and softwood plywood from around the world. This includes an extensive range of UK produced panel products such as Flooring Grade Chipboard, Medium Density Fibreboard (MDF), Oriented Strand Board (OSB) and Hardboard.

We are dedicated to providing sustainable solutions to our customers, keeping the environment at the forefront of our minds. Read more about our timber products and the story behind them, along with some expert advice on getting the most from our timber. 

Types of wood

What are softwoods
Softwoods come from trees that are of the coniferous or evergreen species, such as pine or spruce. These species make up 80% of the world’s production of timber. Pine is used in our range of finishing timbers and decking products, Spruce for our structural and non-structural Carcassing timbers, and Fencing timbers. We can also offer Western Red Cedar and Larch for cladding and tongue and groove products.

What are hardwoods
Hardwoods come from leaf-bearing, deciduous trees, including ‘temperate’ species such Oak, Ash and Walnut as well as “tropical” species such as Sapele and Meranti.  Through our extensive supply-chain we are able to offer hardwoods to suit all applications, from high-quality joinery, to decking, cladding and heavy structural applications.

What are wood plastic composites
Wood plastic composites are a mix of recycled wood, recycled plastic and performative additives such as polythene (PE), polypropylene (PP), polyvinyl chloride (PVC) or polylactic acid (PLA). This combination of ingredients creates a material that is denser, stronger and longer-lasting than standard wood.  This variation of timber is perfect for decking and landscaping purposes. Take a look at our range of composite decking here.

What are structural softwoods
Structural softwood is used where the timber is required for loadbearing purposes, for example, Joists or Roof members. Structural Softwoods in the UK fall mainly into 3 strength grades: C16, C24 and TR26 (which is specifically for Roof Trusses). The grade required will be based on both the cross section of the timber and the loadbearing put on it.
The strength of a piece of timber depends on a combination of the inherent strength of the timber species and the grade of the individual piece. A high grade of timber from a weaker species may be just as strong as a low grade of timber from a strong species. To make specifying easier, species and grades are grouped into strength classes of similar strength for softwoods, higher numbers indicate stronger timber.

What are timber sheet materials
Here at Jewson we understand the demand for a large range of sheet materials, we have added many specialist products to our branches to make sure you get the right timber sheet materials. Sheet materials have many applications from temporary flooring and walling to roofing and carpentry. We stock various sizes of door blanks, pin boards and notice boards, ‘Neat-match’ specialist MDF claddings and veneered MDF alongside more standard sheet materials like our handy panel MDF and Ply.

To find out more about sheet materials, check out our guide written by experts at Jewson!

More on sheet materials

Understanding timber grading

Timber grading is the process of inspecting pieces of timber and categorising them based on their qualities and strength. There are two ways in which timber can be graded. Machine grading and visual grading:

Machine strength grading

Machine grading is based on the relationship between strength and stiffness, and is best suited to grading high volumes of timber of similar species and cross section.
The machine grades each piece and stamps it with the appropriate mark.

Machine grading certficate

Visual strength grading 

Visual strength grading uses the grader’s experience to assess each piece of timber according to rules that define the size, type and number of strength-reducing characteristics allowed in each grade.

Natural strength-reducing features include knots, wane (the uneven edge caused by a residue of bark) and the slope of the grain. Other strength-reducing features, such as splits or shakes (the splitting of the wood fibres along the grain) may have developed as a result of drying.
The grader assesses each piece and stamps it with the appropriate mark.

visual grading certificate

Joinery grading

At Jewson we carefully select the grades used for our PSEs and mouldings to ensure they are suited to our customers’ needs. For example, we use only selected 25mm sideboards (produced from the outer part of the log) for our torus and ogee skirtings to reduce “cupping” and make sure they fit flat to the wall and our 100 x 100 PSE is produced from a specially selected grade, minimising twist and “shake”, to ensure it is fit for use as stair newels and other high-quality joinery applications.

Joinery softwoods
Joinery softwoods are used for finishing timbers such as skirting, architraves, claddings, mouldings, and each piece of timber is graded for appearance based on the Nordic Timber Grading Rules for Pine and Spruce Sawn Timber 2015 and the European standard EN 1611-1 Sawn timber – Appearance grading of softwoods. Each piece is graded on a scale of 1-6 taking into account ‘visual defects’ such as: 

Knots (size, type and frequency)Splits/shakeWane
Insect attackCompression woodResin/bark pockets
Blue stainSlope of grain/wavy grainRot/damage

In “Redwood” (Pine) Grades 1 to 4 are usually packaged together as “Unsorted” which is used to produce higher quality “premium” products. Grade 5 (5ths), is the grade most commonly used for production of standard PSEs and Mouldings in Builders’ Merchants. Grade 6 (6ths) is used for lower quality applications such as packaging
In “Whitewood” (Spruce) grades 1 to 5 are usually packaged together as “Sawfalling excluding 6ths” used for budget PSEs, PTG Flooring, etc. Grade 6 (6ths) is sold separately and used for lower quality applications such as packaging.

GradeRedwood (Pine)Examples of usesWhitewood (Spruce)Examples of uses
1Unsorted (U/S)High quality 'premium' productsSawfalling (S/F)Budget PSEs, PTG, Flooring
55thsPSEs & Mouldings

Making your timber last

The life span of a piece of timber relies on many elements: 

  • Timber species and its natural durability
  • Whether the timber is being used internally or externally
  • Where it is being used, suspended, in ground contact, in contact with soil

We stock a range of treated timber to help extend the life of the wood. We explain below just how we do this, what types of preservatives are applied and which types are available to you. 

Timber preservation
The durability of many commercial softwood timber species can be improved with the application of a wood preservative applied by an industrial process. The process involves a kilning process to dry the timber before it is loaded into a high pressure treatment plant (autoclave) where the preservative is forced into the timber cells under vacuum pressure.

Treatment processes and preservative chemicals
The chemicals used in wood preservatives comply with current EU regulations. They contain specifically targeted biocides that are designed to present a minimum hazard to the wider environment. There are two main types of pre-treatment processes, both carried out by timber suppliers, merchants or joinery companies, in enclosed and strictly controlled industrial vessels.

Vacuum, high-pressure treatment
Suitable for the full range of end uses, but particularly for external applications, both in and out of ground contact. The preservative is forced deep into the cellular structure of the timber, which generally has a green tint. Additives can give either a rich brown colour, usually for fencing and landscaping timbers, or extra water repellency for decorative external timbers, such as decking and cladding timbers.

Double vacuum, low-pressure treatment
Used for building and joinery timbers in Use Classes 1, 2 and 3c. Treatment provides an effective ‘envelope’ protection around the timber and leaves the colour virtually unchanged. A colour indicator, as well as water-repellency, can be added to the treatment if required.

Chain of custody/ Sustainability

At Jewson, we are passionate about preserving the environment and are serious about contributing to a carbon neutral world. Trees absorb CO₂ as they grow, providing a carbon-sink effect, making them a great carbon neutral material. We work hard to ensure we harvest the most sustainable wood possible while simultaneously providing great quality. 

Chain of custody ensures that certified wood is fully accounted for down the supply chain. It documents where timber has come from and that it has come from a legal, reliable source. 
Timber will be harvested from a certified forest, transported by a certified harvester and haulier, delivered to the certified sawmill, then delivered to certified merchant and eventually lands in the hands of the customer – all in an unbroken chain of custody.

Jewson holds certificates for both the two main schemes for chain of custody - FSC ® C014608 (Forest Stewardship Council ®) and PEFC (Programme for the Endorsement of Forest Certification), although there are other certificates available.

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