The double hung timber box sash window has stood the test of time as the perfect functional and aesthetic solution; it offers maximum influx of daylight and easily controlled ventilation. Our double glazed wooden box sash windows retain these features whilst upgrading the thermal and acoustic specifications required of a modern window.

Traditional Manufacturing Methods

All windows manufactured using traditional through mortise and tenon construction, with weight and pulley counter-balance system as standard. Read More

Double Glazed Units Manufactured In-House

We manufacture our own high-spec double glazed units in-house, with unique warm-edge spacer bar and krypton gas filled as standard. As a result, we can meet demanding design specifications, including thermal transmittance, acoustic efficiency, solar and light control, and introducing hand-blown cylinder glass to give the correct visual texture in Grade II listed buildings. Read More

Solid-Through Glazing Bars

Our sash windows are made with individual double glazed units, incorporating a solid-through 20mm glazing bar. The majority of double glazed timber windows produced in this country are manufactured using "applied glazing bars" (small timber beads stuck onto one large double glazed unit to give the impression of individual units). The main weaknesses to this idea being that the stuck-on bars can easily be pulled off and that if the double glazed unit fails for any reason, the complete frame will have to be virtually replaced.

Refined Sight Lines

Sight lines are key to the aesthetic of any window. This is particularly true of Georgian sash windows given their numerous glazing bars. Our use of custom-made independent double glazed units in combination with refined solid-through glazing bars enables us to retain the visual integrity of a traditional box sash window, whilst meeting the demanding thermal and acoustic specifications required of current building regulations. Naturally, this takes more time and effort – but the results are exceptional and the construction is for the long term. 

Current Building Regulation Compliant

Our double glazed windows have been independently tested by the Building Research Establishment Ltd. (BRE) to assess their thermal performance. Finite element thermal modelling simulations were carried out using Physibel Bisco software to accurately determine the exact U-value of our windows. The modelling was carried out using the methods in BS EN ISO 10077-2. The results given by BRE confirm that our windows have a whole window U-value of 1.5 W/m²K, thus giving them compliance with current building regulations for replacement windows and new build projects. 

New build Georgian entrance door and side sash windows


New double glazed box sash windows in grade II listed townhouse, featuring hand-blown glass double glazed units 


New double glazed box sash windows in Georgian farmhouse


Replacement double glazed windows in classic Victorian Herefordshire farmhouse

Replacement double glazed windows with margin lights in early Victorian townhouse