Prime Sash Windows

Bespoke timber sash windows made near London

Prime Sash Windows is a trading name of Skylon Joinery LTD and part of Skylon Group. The company designs, manufactures and installs bespoke timber sash windows, casement windows and doors, working with homeowners, architects and developers. Its workshop is located near London, and the company states that every window is handcrafted there and fitted by FENSA-certified installers. It reports more than ten years of experience in bespoke timber window manufacturing and installation, and more than 500 windows installed.

The company presents itself as a British manufacturer: it states that its windows are designed, built, tested and certified in the UK, rather than imported or assembled from parts made elsewhere. It is a member of The Joinery Network and a FENSA-registered installer, and its products carry PAS24 certification. It also offers free site surveys within 25 miles of London.

Online 3D configurator and instant pricing

A central feature of the service is an online configurator that lets users design sash windows, casements, arches, circles and doors in 3D. The tool updates the price live as the user changes colours, glazing bars, glass and hardware, and it produces a PDF estimate with the full specification. The company states that the design created in the configurator becomes the real manufacturing specification. Users can save their design or request a quote without creating an account.

The process is presented in four steps: configuring the product online, a free survey to take precise measurements and discuss requirements, production in the workshop over four to five weeks, and installation by the FENSA-certified team.

Traditional construction and materials

The company states that its sash windows follow the traditional method: they are built from hardwood, finished with multiple coats of microporous paint and balanced exclusively on lead weights, never spring balances. The lead weights used are 100% recycled. Timber options include hardwood, Accoya and oak, with engineered timber used to prevent warping; the wood is sourced from sustainable forests.

Finishing involves immersion in preprimer, two primer coats and a finish coat, using Sikkens Wood Coatings and Teknos systems. The windows incorporate slimline double glazing and draught-proofing.

Passive Glass and energy performance

Prime Sash Windows offers Passive Glass Technology as an option. According to the company, traditional double glazing achieves a U-value of around 1.4 W/m²K, while its windows with Passive Glass reach U-values as low as 0.8 W/m²K. The company presents this as relevant for architects working on SAP calculations or Part L compliance in heritage projects, where conservation requirements and energy targets must be reconciled.

Warranty coverage

Every product comes with a personalised Certificate of Warranty issued upon manufacture. The warranty covers timber and glass for 10 years, paint finish for 5 years, weatherseals for 5 years and hardware according to the manufacturer, for 5 to 10 years. The company describes the warranty as insurance-backed and provides a dedicated customer service team.

Workshop management and recognition

Orders are managed from quote to installation through JoineryCore, a workshop-management software the company built and runs itself. Prime Sash Windows was a finalist in the Smart Factory 2026 awards, according to an announcement on its site.

Service area and client base

The company serves London and surrounding areas, including Hertfordshire, and works with homeowners, architects and developers. Its workshop is at Unit 3, Leaside Industrial Park, Sedge Green, Nazeing, EN9 2BF.