• Timber Sizing

    | by Holly Wood

    Timber sizing is more than just measuring the length and width of a piece of wood. It’s an integral part of the building process, impacting everything from structural stability to aesthetic appeal.

    In this article, we will delve into the world of timber sizes, including planed timber, imperial and metric measurements, and the difference between nominal and actual sizes.

    Understanding Timber Sizes

    Choosing the correct timber sizes is crucial to ensure proper fitting and structural integrity in any construction or woodworking project.

    From softwood timber to hardwood timber, all grades and types of timber are subject to varying dimensions, and it’s essential to know the standard lengths and widths commonly used in the industry.

    These standard stock sizes simplify the process of acquiring the right amount of material for a project and reduce the need for compiling a complicated cutting list.

    Timber Dimensions

    • Length: Measured in feet or metres.
    • Width and Thickness: Typically measured in inches or millimetres.

    The Distinction between Nominal and Actual Sizes

    Nominal sizes refer to the dimensions of timber before any planing or finishing, whereas actual sizes denote the dimensions after planing and smoothing the wood (finished timber sizes).

    It’s crucial to keep this difference in mind while planning and executing your projects, as it directly impacts the fit and overall aesthetics of the end product.

    Nominal Size

    Nominal size refers to the standardised or “in-name-only” dimensions used in the timber industry.

    These sizes are usually not the exact measurements of the timber but are used for consistency in labelling and purchasing.

    For example, a 2×4 piece of timber doesn’t measure exactly 2 inches by 4 inches. Instead, its actual size tends to be around 1.5 inches by 3.5 inches.

    Actual size

    Actual size, on the other hand, is the true, physical dimensions of the timber.

    Before embarking on your project, ensure you can have access to actual sizes locally (finished sizes) to streamline your timber project as much as possible.

    Imperial and Metric Sizes

    In different regions, timber may be sold using imperial or metric measurements.

    In the UK, all timber must be sold using metric sizes, with millimetres being the standard unit of measurement. However, globally and occasionally within the UK, imperial sizes persist in use.

    Standard Timber Lengths

    Timber beams come in a wide range of lengths to accommodate various construction and woodworking needs.

    Typically, these standard lengths increase in 60cm intervals.

    In our selection, you’ll find common lengths such as 2.4m, 3m, 3.6m, 4.2m, and 4.8m.

    Rough vs. Planed Timber

    • Rough-sawn timber: This type hasn’t been planed after sawing. As a result, it can be somewhat rough to the touch, and its dimensions can be slightly larger than stated.
    • Planed timber (or dressed timber): This wood has been smoothed to a certain degree, resulting in more precise measurements. However, the planing process reduces the size of the timber slightly.

    Planed Square Edge Timber

    Planed square edge timber, often referred to as “PSE,” is a popular choice for many woodworking projects due to its smooth, refined finish.

    This timber is smoothly finished and showcases square edges at 90-degree angles to each other.

    It is available in various thicknesses and widths, making it ideal for a wide range of applications.

    PAR Timber

    “PAR” timber stands for “Planed All Round” timber. It refers to wood that has undergone a planing process on all four sides, resulting in smooth and uniform surfaces.

    The planing process removes any roughness and irregularities from the timber, creating a refined finish that is ready for use in various woodworking and construction projects.

    Factors Influencing Timber Size

    Several elements determine the final size of the timber:

    • Shrinkage: As timber dries, it shrinks. The amount of shrinkage varies based on the wood species and the drying method used.
    • Sawing technique: Different sawing techniques, like plainsawn, riftsawn, or quartersawn, can influence timber dimensions and grain appearance.
    • Regional standards: Different countries have different standards for timber dimensions. Ensure that you’re aware of regional variations if sourcing timber internationally.

    Historical Methods of Sawmilling

    In the era before sophisticated machinery and precision tools, craftsmen relied on manual processes to shape timber into functional and artistic pieces.

    While modern technology has propelled the timber industry forward, exploring the historical methods that have laid its foundation is paramount.

    By bridging the gap between the past and the present, we enrich our craftsmanship, preserve the essence of our cultural heritage, and ensure that the beauty of timber sizing and usage endures for generations to come.

    Below are some of the historic methods of sawmilling:

    • Hand tools: Craftsmen relied on traditional hand tools such as chisels, saws, planes, and axes for shaping timber.
    • Joinery techniques: Traditional joinery methods like dovetail joints, mortise and tenon, and tongue and groove were extensively used for strong and durable connections.
    • Hand carving: Intricate designs and decorative elements were meticulously hand-carved to add artistic flair to timber pieces.
    • Timber seasoning: Prior to modern kilns, timber was seasoned and dried naturally to reduce moisture content and prevent warping or cracking.
    • Timber sizing by eye: Experienced craftsmen gauged dimensions visually, using their expertise to achieve accurate measurements without modern measuring tools


    In conclusion, timber sizing is a critical aspect of any construction or woodworking project. Understanding the difference between nominal and actual sizes, imperial and metric measurements, and the various types of wood sizes available from timber merchants can significantly impact the success of your endeavours.

    With this knowledge under your belt, you’ll be ready to tackle any project with confidence!

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