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    Video Tutorial 8:15 mins

    How to Measure Your Windows

    Accurate measurements are essential for a perfect fit. Follow our step-by-step video guide to measure your windows correctly.

    Video Coming Soon

    Our measurement tutorial video is currently in production

    Use Steel Tape

    Not fabric or plastic

    3x

    Measure Thrice

    At top, middle, bottom

    mm

    Use Millimetres

    For precision accuracy

    Video Timeline

    0:00

    Tools You'll Need

    Steel tape measure, notepad, pencil, and spirit level

    0:45

    Width Measurement

    Measuring the reveal width at three points

    2:00

    Height Measurement

    Measuring the reveal height at three points

    3:30

    Depth Check

    Ensuring adequate depth for the secondary glazing system

    4:45

    Squareness Test

    Checking diagonals to verify the window is square

    6:00

    Obstruction Check

    Identifying handles, locks, and other potential obstructions

    7:15

    Recording Measurements

    How to document and submit your measurements

    Common Mistakes to Avoid

    • ✕Measuring the glass instead of the reveal
    • ✕Taking only one measurement per dimension
    • ✕Forgetting to check for obstructions
    • ✕Not accounting for uneven reveals

    Prefer Written Instructions?

    Check out our detailed written guide with diagrams and a printable measurement sheet.

    View Written Guide

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    Sources & References
    AI-verified

    Authoritative sources supporting the information in this article.

    1. British Standards Institution (BSI) (2021). Laboratory measurement of sound insulation of building elements. Measurement of airborne sound insulation. BS EN ISO 10140-2:2021.Open source

      This is the primary British Standard for measuring and evaluating the sound insulation performance of buildings and building elements, essential for secondary glazing acoustics.

    2. Department for Levelling Up, Housing and Communities (2021). Approved Document L1A: Conservation of fuel and power in new dwellings (and Document L1B for existing dwellings). HM Government - Building Regulations 2010.Open source

      Provides the legal requirements for thermal efficiency (U-values) and air tightness in UK dwellings, which governs why precise measurements are needed for secondary glazing.

    3. Historic England (2016). Secondary Glazing for Energy Efficiency and Noise Reduction. Historic England Technical Advice Note.Open source

      An essential guide for measuring and installing secondary glazing in heritage sites, ensuring that measurements do not impede the operation of original shutters or damage historic fabric.

    4. British Standards Institution (BSI) (2016). Windows and doors. Code of practice for the survey and installation of windows and external doorsets. BS 8213-4:2016.Open source

      This standard provides the specific requirements for measuring and designing window installations to ensure structural integrity and weather tightness.

    5. Glass and Glazing Federation (GGF) (2020). GGF Glazing Manual: Surveying and Installation Guide. GGF Section 5: Secondary Glazing.Open source

      The industry-standard technical manual for the UK glazing industry, offering detailed guidance on tolerances and measurement techniques for window additions.