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Sash Windows in a traditional house

Box Sash Windows

Harnessing timeless designs and superior craftsmanship, we at the Traditional Window Company specialise in the creation of bespoke box sash windows, an embodiment of the UK’s rich architectural history. Every traditional sash window we construct is meticulously tailored to align with the original design, preserving the distinct period character of your home.

Our precision in crafting the original sash windows ensures a perfect fit within the original openings, delivering a seamless and classic finish. These unique box sash window details and our commitment to quality have made us a preferred choice for architects, discerning homeowners, and professionals working with Conservation Areas and Listed Buildings.

We’re not just a window company; we’re artisans dedicated to the restoration and preservation of the UK’s architectural heritage through our exceptional sash windows and box sash windows.

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    Beautiful, Traditional Handmade Sash Windows

    Each traditional sash window is individually made following the period detail, profiles and proportions of the original, including sash horns, cord and weight mechanisms. Our bespoke box sash windows consist of traditional joinery and design gleaned from over three centuries, combined with modern technology.

    Key features of our sash windows

    • The latest double glazed sealed units draught/weather seals
    • Modified timbers with a 50 year guarantee not to rot or warp
    • Advanced micro-porous paint covers with 10 year warranty
    • Internally beaded glazing to maximise security and weather seal

    All points help to maximise thermal insulation, durability and safety/security.

    Examples of our sash windows

    Sash Windows


    2 years ago, we had 10 new wooden sash windows made and installed. This was after initially approaching 10+ companies and meeting up with 3. As I type this they are back at our house replacing the whole of our front elevation being 4 sash and 6 casement windows, so as you can tell we think their windows are great …. PS I am a Chartered Surveyor and would not recommend lightly.

    Mr Talbot,W4

    From day one TWCC were impressive providing sound advice and a detailed quotation with options. Their products and quality workmanship are second to none and their fitters are highly skilled and leave little mess behind. Keep up the good work – our house looks better and is much warmer!.

    Mr Vasdekys, W12

    Thank you for creating and installing such good quality windows to meet our ever-changing designs. We are very happy with the results and are already recommending you to friends and family.

    Mr Rock, N10

    I had delayed replacing the original windows to my Edwardian house as I feared losing the fine detail and elegance, but The Traditional Window & Conservatory Company were the answer!. They replicated the exact appearance of the original windows–but what an improvement to both the heatand sound insulation!!. I am delighted! The company employees and representative were also polite,helpful and efficient. Thank you.

    Ms Campbell, TW1

    Before installation rooms and walkways are sheeted up and the old windows are removed from site and disposed of. Our expert fitters will ensure the replacements are hand finished and trimmed off with internal stub sills, architrave and period trim to mirror the originals. The immediate walls surrounding the window are decorated where applicable to complete the finished look.


    Stable timbers that enhance paint coating lifespan is the key to the long life of a window because if the coating remains intact, the window will last indefinitely.

    Accoya®A modified timber and one of the world’s leading, long-life woods with a 50 year warranty against rot and warping.
    Laminated TimberVacuum/pressure, Protim water based treated Redwood with a 30year warranty against rot and warping
    Natural FinishLight oaks, Douglas Fir and Red Grandis with a 30 year warranty


    Glass & Glazing TypesGlazed to ‘A’ rated specification mainly consisting of 20mm Optiwhite glazing double glazed sealed units (4-12-4). This provides a centre pane U-value of 1.2w/m2k (the lower the number, the better the thermal insulation); The use of OptiwhiteTM glass helps to provide high visual clarity and purity of colour as there is no green tinge associated with some double glazing. This glass also gives more solar heat gain since it allows more heat from the sun, which can save on energy bills during the winter months.
    Other Glazing
    • Toughened glass for safety
    • Laminated glass for security and safety
    • Acoustic glass to reduce sound transmission from road traffic, aircraft, trains etc. (example installations available to consult)
    • Obscure glazing, etched, patterned or textured for privacy or design
    • Leaded glazing with antique patina finish to mirror original leads
    • Traditional decorative coloured leads to mirror original design
    • Slim 7,9,11,12 or 14mm double glazed units for Conservation areas and Listed Buildings where solid glazing bars and traditional putty bead are required
    • Easy clean glazing; a consideration for out of the way windows i.e. mansard roofs
    • Solar control glazing to help block the sun’s radiant heat especially for high exposed south facing windows
    • Curved double glazed units to help replicate the original window curved profiles.
    Draught/WeatherproofingTo enhance the thermal insulation of the window, high specification seals, concealed within the window structure, are positioned so that they can be easily replaced if and when necessary.


    FinishesThe latest, most advanced micro-porous treatments and finishes are used to maximise longevity and minimise future maintenance.
    • We can colour match specified paint colours
    • Dual colour option available in or out
    • Natural wood finish in low maintenance pigmented micro-porous stains
    • Traditional box sashes fitted with high quality ironmongery in brass, chrome shiny or matt finish (other materials available)
    • High quality pulleys in matching material with pre-stretched sash cords and lead weights to maximise opening of sashes and ensure smooth, effortless operation.
    • Modern spring/spiral balance where required
    Safety & SecuritySecurity, lockablesash fasteners and 2 (No.) sash stop locks fitted to each window, including child safety/ventilation locks as standard.


    What is special about the Box Sash Windows from the Traditional Window Company?

    Our Box Sash Windows are individually handcrafted following the period detail, profiles, and proportions of the original. They are designed to match the original design and retain the period character of your home whilst maximising thermal insulation.

    What are the key features of your Box Sash Windows?

    Our Box Sash Windows feature the latest double-glazed sealed units, draught/weather seals, and modified timbers with a 50-year guarantee against rot or warping. They also have advanced micro-porous paint covers with a 10-year warranty and internally beaded glazing to enhance security and weather seal, and heat insulation.

    What type of timber is used for your Box Sash Windows?

    We use a variety of high-quality timbers for our Box Sash Windows, such as Accoya®, Sapele, laminated timber, and natural finish woods like light oaks, Douglas Fir, and Red Grandis. All our timbers come with warranties against rot and warping.

    What kind of glass and glazing do you use in your Box Sash Windows?

    We use ‘A’ rated 20mm Optiwhite double glazed sealed units for the majority of our windows, but we also offer a variety of other glazing options such as toughened glass for safety, laminated glass for security, acoustic glass to reduce sound transmission, and more including heritage/historic glass. We can customize the glazing to meet your specific needs.

    How are your Box Sash Windows installed?

    Our experienced team handles the installation process with care, ensuring minimum disruption. We remove and dispose of the old windows, and then install the new ones, finishing them off with internal stub sills, architrave, and period trim to match the original design. The immediate walls surrounding the window are made good/decorated applicable to complete the look.

    What finishes do you offer for your Box Sash Windows?

    We use advanced micro-porous treatments and finishes for our Box Sash Windows to maximise longevity and minimise maintenance. We can colour match specified paint colours, provide a dual colour option, and offer natural wood finishes.

    How do you ensure the security of your Box Sash Windows?

    Our Box Sash Windows are fitted with security, lockable sash fasteners and two sash stop locks per window, including child safety/ventilation locks as standard.

    Can you install Box Sash Windows in conservation areas and listed buildings?

    Yes, we are experienced in working with planning requirements for conservation areas and listed buildings. We have undertaken many successful planning applications and appeals to The Planning Inspectorate.

    What kind of ironmongery is used in your Box Sash Windows?

    Our Box Sash Windows are fitted with high-quality ironmongery available in brass, chrome shiny or matt finish. They feature high-quality pulleys with pre-stretched sash cords and lead weights for smooth, effortless operation.

    Conservation Areas & Listed Buildings

    We are conversant with the requirements for planning and have undertaken many successful Planning applications and where required, successful appeals to The Planning Inspectorate.

    Fensa Building Regulation Certificate of Compliance

    Where applicable for windows and doors we will arrange certification following installation.

    Our Accreditations

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