Qualifying standards

Wood Window Alliance manufacturers and their suppliers commit to a high standard of quality and performance of materials and components used in window manufacture and installation. This commitment is supported by: independent testing to European Standards (BS EN 942, timber; BS 644: 2009, timber beads; BS EN 927-1, paints and varnishes; BS EN 599, preservative treatments); conformance declarations; third-party UK accreditation schemes such as: TRADA Q-Mark, BSI, TWAS, FENSA; and recognised European accreditation schemes, and Chain of Custody certification.

Some members also offer additional accreditation relating to specific market areas or customer requirements.

The sections below summarise the main technical features and standards incorporated in the Wood Window Alliance promise and also highlight some of the additional benefits members may offer.

Window design

All Wood Window Alliance timber windows are manufactured in accordance with BS 644: 2009. Key features include:

Timber frames

Frames comply with EN 942: clear faced sashes and components, defect-free and manufactured from heartwood or laminated timber components. Timber durability to Hazard Class 3 or higher, achieved by appropriate preservative treatment (EN 599) or incorporation of modified timber or a high percentage of heartwood.

Glazing beads

Manufactured from timber, modified timber, aluminium or wood-plastic composite material. Timber beads have rounded edges, drained rebates with capillary gaps, and are fully coated in accordance with BS 644: 2009.

Joints and sills

All joints fully coated with D3/D4 adhesive (Din EN 344), filled as necessary, and all exposed end-grain sealed. Sills manufactured from treated timber, modified timber, aluminium or wood-plastic composite material.


Chain of Custody certification.

Factory applied coatings

Conform to the durability matrix described in BS EN 927-1: Paints and Varnishes - Coating Materials and Coating Systems for Exterior Wood - Part 1: Classification and Selection. All surfaces coated in accordance with BS EN 927 to a minimum coating thickness of 120u dft. All coatings water-based, with no heavy metal additives, and with Volatile Organic Content below 50g/l.


Factory fitted double or triple-glazing units (removable for safe site installation where required) manufactured to appropriate British Standards Glazing units shall be fitted with drained and vented up stand. Glazing units fitted to fully coated, drained and vented up-stand for extended unit life.

Supply, installation and maintenance

Windows supplied on dedicated transport, to controlled site storage, and installed by qualified installers e.g. FENSA. Aftercare instruction on maintenance procedures and frequency in accordance with BS EN 927-1:Paints and Varnishes - Coating Materials and Coating Systems for Exterior Wood - Part 1.

Performance standards

Weather performance

Windows meet the performance requirements defined in BS 6375 Parts 1 and 2, relating to weather tightness, operation and strength characteristics.

Energy performance

Windows meet the requirements of UK Building Regulation Approved Document L: 2013‚ Conservation of Fuel and Power, England and Wales or equivalent regulations for Ireland/Scotland/Northern Ireland.

A, B or C window energy rating, supported by BFRC Energy Rating, whole window U-values or centre pane U-value as appropriate.

Ventilation according to UK Building Regulation Approved Document F (Ventilation): 2010, Conservation of Energy and Power, England and Wales or equivalent regulations for Ireland/Scotland/Northern Ireland.


Locking system security accordance with BS 6375 Part 3: 2009 Annexe A.

Windows and doors for new buildings tested and certified to PAS24 in compliance with Approved Document Q.

Members may additionally offer BS 7950 Secured-by-Design and BS EN ISO 10140 acoustic performance certification where required.

Manufacturing control, performance declaration and auditing

Factory production control

All manufacturing members have a factory production control (FPC) system supporting their declarations of performance and CE marking program, accredited by the WWA.

Members may additionally quote third party accreditation schemes such as TRADA Q-Mark, BSI, TWAS or equivalent European scheme.

Performance declarations

Test evidence, in support of performance specifications, is provided, where appropriate, from approved suppliers e.g. security fastenings, glazing parameters, sourcing documentation.


Members' factory control systems are subject to independent annual audit, in line with EU regulation.

Membership is subject to annual review based on completion of the Wood Window Alliance self-declaration submission and appropriate supporting evidence where changes from previous years have been made.

Current members are issued with an annual membership certificate, listed on the website, and authorised to use the Wood Window Alliance logo on their literature and marketing material following review and acceptance of their self-declaration submission and relevant documentation.


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