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At Nine Zero, we specialise in crafting timber box sash windows that honour the elegance of the past while embracing the performance demands of today. Designed to preserve the character of period homes and elevate new builds alike, our bespoke windows combine time-honoured joinery with cutting-edge insulation, security, and sustainability. 

Working with professionals and homeowners alike, we produce each window from our Cornwall headquarters, with a reliable 6-8 week turnaround time and upfront quotes for all work.

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What are box sash windows?

Box sash windows are a classic style of vertical sliding window, traditionally found in Georgian, Victorian, and Edwardian homes. Beloved for their timeless proportions and elegant sightlines, box sash windows are an architectural staple across London and many other locations across the South West.

 

How do box sash windows work?

Unlike spring sash alternatives, box sashes operate using a system of weights and pulleys hidden within a timber frame or “box” on either side of the window. This allows the sashes to glide open and close smoothly while maintaining perfect balance.

Partnering with developers

We work with developers on bespoke windows and doors for their renovation and new-build projects. We offer stellar products, fast turnarounds, and competitive upfront quotes.

Working with developers

Our bespoke approach to timber box sash windows

All of our box sash windows are tailored to a property’s exact needs. From traditional horns and lambs’ tongue mouldings to glazing bars, ironmongery, and frame profiles, every detail is customisable.

Choose from a range of glass options, paint finishes, and sustainably sourced timbers to achieve the perfect blend of form and function. Our expert team will be happy to offer guidance throughout the process, ensuring precise measurements, seamless fitting, and a final product that honours each home’s unique character.

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Why choose Nine Zero's box sash windows?

Secure

Secure

Our doors offer enhanced security with Document Q and PAS 24 compliance, multi-point locks, and internally beaded glazing.

Sustainable

Sustainable

We use FSC-certified sustainable materials, recycle timber waste, and supply renewable energy to local communities.

Quality

Quality

We use Engineered Redwood, Engineered Red Grandis and Abodo sustainable timber wherever possible, using the highest standards of renewable wood.

Insulated

Insulated

Our timber doors are natural insulators with little thermal conductivity, offering U-values as low as 1.0 W/m2K and reduced energy bills.

Easy clean

Easy clean

Our doors are low-maintenance designs, with simple frames and durable finishes for effortless cleaning and minimal maintenance.

Weatherproof

Weatherproof

Our doors are resilient and built to last in all climates; Nine Zero external timber doors meet BS 6375:2015 Parts 1 and 2 regulations for weathertightness.

Why choose Nine Zero for custom-made windows?

Our windows are the result of expert craftsmanship, sustainable sourcing, and meticulous attention to detail. Each window is handcrafted in Cornwall using FSC-certified timber, chosen for its durability, beauty, and low environmental impact. We combine traditional joinery techniques with modern engineering to deliver products that exceed expectations in both performance and appearance.

Whether you’re restoring a listed Georgian townhouse or designing a new property with period character, our windows are tailored to suit your needs. Designed to meet rigorous standards, they provide enhanced insulation, soundproofing, and protection. With every project, we honour the aesthetic of classic British architecture while upgrading homes with the comfort and efficiency of the 21st century.

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Made to measure for heritage properties

We provide a full suite of downloadable CAD drawings, technical datasheets, and performance specifications. These resources ensure clear communication from planning through to installation, supporting compliance and seamless execution. 

Explore individual product specs or view our full technical range to access everything you need to design with confidence.

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Our technical information

We provide a full suite of downloadable CAD drawings, technical datasheets, and performance specifications. These resources ensure clear communication from planning through to installation, supporting compliance and seamless execution. 

Explore individual product specs or view our full technical range to access everything you need to design with confidence.

Datasheet
Full technical range

Our guarantees

Every Nine Zero box sash window is built to last and backed by industry-leading guarantees. We offer a 30-year warranty on our sustainably sourced timber and 10-year coverage on workmanship, glazing, and paint finishes. Each product undergoes rigorous testing to ensure long-term performance in real UK conditions. 

For full details, including terms and care recommendations, please visit our warranty page.

Warranties

Design your ideal wooden sash windows

Whether you’re restoring a period property or planning a new build with heritage appeal, our handcrafted timber sash windows bring timeless elegance and modern performance to every project. Speak to our expert team today for tailored advice, a no-obligation quote, or to start designing your perfect windows.

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FAQs

Are box sash windows suitable for modern homes?

Absolutely. While traditionally associated with period properties, box sash windows are also an elegant choice for new builds. At Nine Zero, we combine heritage aesthetics with modern performance, making our windows ideal for any home seeking timeless style with contemporary benefits like thermal efficiency and enhanced security.

Can these windows be installed in conservation areas?

Yes. Our Heritage Range is specifically designed for listed buildings and conservation areas. With authentic details, slimline glazing, and traditional joinery options, we meet the requirements of most planning authorities, and our team can support you throughout the approval process.

What maintenance is required?

Thanks to engineered timber and high-performance paint finishes, our windows require minimal upkeep. Occasional cleaning and inspections of the coating will help preserve its beauty and performance for decades.

Where does Nine Zero work?

We work with homeowners, architects, and developers across, Greater London, Surrey, Hampshire (particularly Winchester), Bristol and the Wider South West Area (particularly Gloucestershire and Somerset).

Become a Nine Zero trade partner

Help us to help you. Nine Zero trade supply partners get personalised service, preferential rates, marketing support and direct access to our expert team. Email accounts@nine-zero.co.uk to find out more.

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Sustainability

Environmental consciousness and sustainability are essential if we are to preserve a healthier planet for future generations. That’s why we’ve made a significant commitment to eco-friendly practices by establishing Nine Zero in the heart of Cornwall.

Since 2017, drawing on over 15 years of supplier expertise from our sister company Sash Windows London, we’ve set the bar for sustainable timber windows and doors. This was more than just an expansion; it represents our unwavering dedication to meet the growing demand for green building materials, while upholding the premium quality and unparalleled expertise that our customers have come to rely on.

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Request a brochure

To explore our range of sustainable timber windows and doors and imagine the possibilities for your project, request a Nine Zero brochure by contacting our team today.