Bespoke Timber Sash Windows

The Traditional Box Sash Window, Perfected

The box sash window is one of British architecture's most enduring designs. Two sashes slide vertically within a concealed box frame, counterbalanced by lead weights on cotton cords. The mechanism is elegant, reliable, and proven over three centuries. At Prime Sash Windows, we manufacture bespoke timber sash windows that preserve this traditional construction while delivering the thermal, acoustic, and security performance modern homeowners expect.

Every window is built to order in our workshop near London. There are no standard sizes — each frame, sash, and glazing bar is manufactured to your exact dimensions and specification.

Specification

• Timber — engineered Accoya (50-year guarantee) or premium hardwood. Laminated sections prevent warping.
• Glazing — slimline double glazed 4/16/4 sealed units. U-value 1.4 W/m²K. Part L compliant. Triple glazing available.
• Security — PAS24 multi-point espagnolette locking on all opening sashes.
• Counterbalance — traditional lead weights on cotton cords. No spring balances.
• Draught seals — discreet brush and compression seals on all sliding surfaces.
• Glazing bars — Georgian, Victorian, cottage, or plain. Planted or run-through.
• Colour — any of 2,000+ RAL colours, full Farrow & Ball range. Dual colour (different interior/exterior) available.
• Hardware — Fitch fasteners, sash lifts, sash pulls in polished brass, satin chrome, or black.
• Finish — factory spray-finished with Sikkens coatings (primer, undercoat, topcoat).
• FENSA registered — Building Regulations self-certification on completion.

Guide Pricing

Prices include double glazing, white finish, and standard hardware. Colour, glazing bars, and hardware upgrades priced in the 3D configurator.

Sash Window Styles

• Georgian — six-over-six or eight-over-eight glazing bars with slim run-through profiles and traditional horns.
• Victorian — two-over-two or one-over-one with horns and a slightly wider meeting rail.
• Edwardian — top sash divided with glazing bars, bottom sash plain glass.
• Cottage style — unequal sash heights, with the smaller sash at the top.
• Arched — gothic, segmental, and true-arch heads for period properties.
• Circle and shaped — round, oval, and bespoke shapes for feature windows.

Why Timber, Not uPVC?

uPVC sash windows attempt to replicate the appearance of timber but fall short in several critical ways. uPVC frames are thicker and bulkier — the sightlines never match a genuine timber window. uPVC cannot be repaired; when it fails, the entire frame must be replaced. It yellows and degrades over 20 to 25 years. And in Conservation Areas, uPVC is frequently refused by planning officers.

Timber sash windows can be maintained and refinished indefinitely. Our Accoya timber is dimensionally stable, rot-proof, and carries a 50-year structural guarantee. When spray-finished with Sikkens coatings, the first repaint is typically not needed for 8 to 12 years.

Conservation Areas & Listed Buildings

Many period properties fall within Conservation Areas where window replacements must replicate the original design. We produce windows with authentic profiles — slim meeting rails, ovolo or chamfer beading, run-through horns, and traditional putty-line sightlines. For Listed buildings, we work with heritage officers and supply detailed drawings where planning approval is required.

How It Works

• 1. Design online — Use our 3D configurator to design and price your sash windows instantly.
• 2. Free survey — We visit your property, measure precisely, and confirm the specification.
• 3. Manufacture — Your windows are built in our workshop. Typical lead time 6–8 weeks.
• 4. Installation — Our FENSA-certified fitting team installs your windows with minimal disruption.

Areas We Cover

We manufacture and install bespoke timber sash windows across London, Hertfordshire, and the Home Counties. Free site surveys within 25 miles of London. We also deliver nationwide for supply-only orders. See our location pages for London, Chelsea, Kensington, Hampstead, Richmond, and St Albans.