Spring Balance Sash Windows: Modern Functionality with Traditional Style

• 22 December 2025|
• News

When specifying windows for period properties or historically-informed new builds, architects and developers face a familiar challenge: how to achieve authentic aesthetics while meeting modern performance standards. Spring balance sash windows offer an elegant solution, combining the visual appeal of traditional sliding sash design with contemporary efficiency and ease of maintenance.

For projects where building regulations, budget constraints, or structural considerations make traditional weight-and-pulley systems impractical, spring-balanced mechanisms provide a viable alternative without compromising on appearance.

 What are spring balance sash windows?

Spring balance sash windows operate using concealed spiral balances rather than the traditional weight-and-pulley system found in box sash windows. These spiral mechanisms are housed within the window frame itself, eliminating the need for deep box sections that accommodate weights and pulleys.

The springs counterbalance the weight of each sash, allowing smooth vertical operation while maintaining a slimmer profile. This makes them particularly suitable for new build projects where wall cavities are limited, or renovations where space is at a premium.

From the exterior, spring balance sash windows are visually indistinguishable from traditional designs. The sliding mechanism, glazing bars, and period detailing remain authentic, making them an appropriate choice for conservation areas and heritage properties where planning requirements demand historical accuracy.

Where spring balance sash windows work best

New build residential developments

Developers regularly specify spring balance sash windows for projects where build costs need to remain competitive but the aesthetic outcome must still satisfy planning requirements or market expectations. The slimmer frames suit modern construction details while delivering period appearance.

Conservation area developments

Where new buildings are constructed within conservation areas, spring balance sash windows provide an authentic visual result without the structural complications of accommodating traditional box sections.

Retrofit projects with limited cavity depth

When replacing windows in properties where wall thickness or internal finishes restrict available space, spring balance mechanisms offer a practical solution.

Commercial buildings

For projects requiring historically-appropriate fenestration but prioritising ease of maintenance and longevity, spring balances reduce ongoing service requirements.

Smaller windows

For window openings where the sash weight is relatively light, spring balance mechanisms are particularly effective. They work efficiently across a wide range of sizes, though are especially suited to standard residential window dimensions.

Performance specifications

Lomax + Wood’s spring balance sash windows meet rigorous performance standards:

Security: Tested to PAS24:2016, with internally glazed sashes providing anti-burglar protection. Polished chrome key-locking sash catches come as standard, along with self-engaging top sash locks and restrictors.

Weather performance: Tested to BS 3675 Parts 1, 2 and 3, with weather-stripping for both thermal and acoustic performance.

Acoustic insulation: Standard specification achieves 38dB noise reduction with acoustic glass, or 42dB with enhanced acoustic glazing. Additional acoustic seals can be incorporated depending on project requirements, with testing available to BS EN ISO 10140-2:2010.

Thermal efficiency: Factory double glazing with 4/16/4 toughened/toughened low-e argon fill meets Part L requirements, with alternative specifications available including 4/14/6 toughened/laminated configurations.

Certification: All windows are CE marked to EN 14351-1+A1:2010, providing documented evidence of conformity for Building Control purposes.

Material and finish options

All windows are made using responsibly sourced FSC® or PEFC certified timber including Engineered Redwood, Hardwood, Oak or Accoya, with custom sizing and various colour finishes available. Each product is made to order, allowing us to meet specific architectural requirements while incorporating practical features such as secure locking systems, durable finishes, and appropriate glazing options to improve comfort and efficiency.

Standard specification includes Engineered European Redwood with a hardwood cill, finished with a three-coat white factory-applied micro-porous paint system in RAL 9010. However, we can offer virtually any colour in paint finishes or a range of natural stains.

Lomax + Wood’s spring balance sash window range

Our made-to-order spring balance sash windows are designed for architects and developers seeking historically accurate aesthetics combined with modern performance.

Standard features include:

• Spring balanced sash operation with smooth vertical movement
• Elegant 20mm wide ovolo glazing bars matching traditional profiles
• Timber parting beads for authentic detailing
• Internally glazed design for security and easier maintenance
• Comprehensive weather-stripping for thermal and acoustic performance
• Factory finished to site-ready condition
• Supply and fit service available, providing single point of contact throughout the project

For projects requiring strictly traditional specifications, we also manufacture traditional box sash windows with weight-and-pulley mechanisms, and single glazed windows for listed buildings and heritage properties where conservation requirements demand period-accurate construction methods.

Whether you’re working on a new build development requiring cost-effective period-style fenestration, or a sensitive heritage project where modern performance must be balanced with authentic appearance, our technical team can advise on the most appropriate solution.

Lomax + Wood: made-to-order timber spring balance sash windows

Whether you’re specifying windows for a new development, planning a heritage restoration, or working on a contemporary project requiring traditional aesthetics, Lomax + Wood’s technical team can provide guidance on the most appropriate solution for your requirements.

Contact us today for a free quotation or to discuss your project – complete our online contact form, or  call our team directly on 01277 353857.