Sash Windows

Sash Windows

Traditional British heritage style. Modern performance. Period-correct detail.

Sash windows — two vertically sliding sashes in a single frame — are the defining window style of the British Georgian, Victorian and Edwardian eras. Modern sash windows preserve the period detailing (sash horns, astragal bars, deep bottom rails) while delivering the thermal, security and operational performance a contemporary home requires.

We supply vertical sliding sash windows in three profile systems: REHAU Heritage Vertical Slider and Liniar Vertical Sliding Sash in uPVC, and Smart VS 600 in aluminium — covering conservation-area replacements, period-property refurbishments, and contemporary projects wanting a sliding-sash aesthetic.

Why Choose a Sash Window?

Period-correct aesthetic	Deep bottom rails, sash horns, astragal bars and traditional sash furniture (brass pulleys, sash lifts, fasteners) replicate the look of genuine timber sash windows — critical for conservation officers and period-property owners.
Conservation-area compliant	Local planning authorities often require “like-for-like” replacement of original timber sashes on listed buildings and in conservation areas. A correctly specified uPVC or aluminium sash satisfies these requirements at a fraction of the cost and maintenance of genuine timber.
Space-efficient	Sashes slide vertically within the frame — no internal or external swing clearance required. Ideal for narrow streets, ground-floor rooms with furniture against the wall, and anywhere outward-opening casements would project over a pavement.
Tilt-for-cleaning on most systems	Modern sashes tilt inward for cleaning the external face of the glass from inside the room — addressing the classic downside of traditional timber sashes, which could only be cleaned externally.
Modern energy performance	Triple-brush draught seals, double-glazed sealed units and A-rated energy performance make today’s sash windows dramatically more efficient than the draughty timber originals they replace.
Sash restrictors for child safety	Optional sash restrictors limit the opening to 100mm — satisfying child-safety requirements in schools, nurseries and rental properties without compromising the period aesthetic.

Profile Systems at a Glance

	REHAU Heritage VS	Liniar VSS	Smart VS 600
Material	uPVC (three-chamber sash)	uPVC	Aluminium
Energy rating	A-rated	WER A+	WER C
Best U-value	1.2 W/m²K	Not stated — A+ rated	1.6 W/m²K (overall)
Balance mechanism	Spring balance with traditional weights look	Spring-balance	Spiral spring balance (Caldwell hardware)
Sash options	Slim / intermediate / large	Standard VS + Mock Sash Horn variant	Single size — 28mm glazing, 126mm frame depth
Max sash size	Configurable	Configurable	1600mm wide × 2800mm high; 50kg max per sash
Best suited for	Strict conservation areas, heritage specifications	Mainstream residential period replacement	Commercial, schools, hospitals, flush-fit heritage

REHAU Heritage Vertical Slider

REHAU’s Heritage Vertical Slider is purpose-designed for the UK heritage market. It uses a three-chambered sash profile with three size options (slim / intermediate / large) so the proportions can be matched to the period of the property — critical for Georgian vs Victorian vs Edwardian elevations.

Key period-correct details:

• Deep bottom rail — replicates the visual weight of a genuine timber sash
• Triple brush seals — eliminate the draughts that plague unrestored timber sashes while maintaining a traditional look
• Full sash furniture compatibility — takes all traditional ironmongery including sash horns, astragal bars, brass pulleys, sash lifts and fasteners
• U-value of 1.2 W/m²K — A-rated, exceeding Part L building regulations (1.6 W/m²K threshold)

REHAU Heritage is the specification of choice when conservation officers are strict or when matching existing original sashes on a listed building.

Liniar Vertical Sliding Sash & Mock Sash Horn

Liniar offers two approaches to the sash-window aesthetic:

• Vertical Sliding Sash — a true sliding sash window with WER A+ energy rating, spring-balance mechanism for smooth operation, Yale locks and sash restrictors as standard. Available with authentic sash horns and astragal bars for period properties.
• Mock Sash Horn Window — a casement-style window with sash horns and astragal bar detailing, giving the appearance of a sash from the outside. The operation is casement (outward-opening), which means it’s cheaper, more thermally efficient and easier to clean than a true sash — while still reading as period-correct from the street.

The Mock Sash Horn is a smart compromise where visual impact matters but budget or energy performance rules out a true sash. Both carry Liniar’s 10-year guarantee.

Smart Systems VS 600 (Aluminium)

Smart VS 600 is an aluminium vertical slider aimed primarily at the commercial and institutional market — schools, hospitals, and heritage buildings where aluminium’s durability and low maintenance outweigh its thermal performance disadvantage over uPVC.

Key features:

• Tilt-in facility for internal cleaning — both sashes rotate inward on their pivots
• Flush opening — no internal or external projection, making it ideal for corridors or circulation spaces
• Max sash: 1600mm wide × 2800mm high, 50kg per sash
• Glazing: 28mm sealed units; frame depth 126mm
• Hardware: Caldwell spiral spring balances — industry standard for heavy aluminium sashes
• U-value: 1.6 W/m²K (WER C)

VS 600 is designed for Georgian and Victorian-aesthetic aluminium replacements. For traditional uPVC sash on a period residential property, specify REHAU Heritage or Liniar VSS.

Sash vs Casement — Which is Right for the Property?

	Sash Window	Casement
Operation	Vertically sliding sashes	Side-hinged, opens outward
Aesthetic	Georgian / Victorian / Edwardian / Heritage	Traditional UK residential or contemporary (flush sash)
Conservation-area fit	Normally the required replacement style	Acceptable with flush-sash variant
Thermal performance	1.2 W/m²K (REHAU); A+ rated (Liniar)	0.8 W/m²K achievable
External swing	None — slides within frame	Projects outward when open
Price	Premium	Cost effective

At a Glance — Featured Styles

• REHAU Heritage VS
• Liniar Mock Sash

Frequently Asked Questions

Are uPVC sash windows acceptable in a conservation area?

Often, yes — provided the profile proportions, sash horn detailing and glazing bars are correctly specified. REHAU Heritage Vertical Slider and Liniar Vertical Sliding Sash are both designed to meet conservation-officer requirements on most projects. Some listed buildings and the strictest planning authorities may still require timber; always check with the local conservation officer before ordering.

Can I have sash horns and astragal bars on modern uPVC sash windows?

Yes. Both REHAU Heritage and Liniar Vertical Sliding Sash accept traditional sash horn profiles and glazing bar details — including astragal bars (internal), Georgian bars (between panes), and duplex bars (internal and external). These are the details that make a uPVC sash read as period-correct from the street.

Do modern sash windows tilt inward for cleaning?

Yes — this is a major advantage over genuine timber sashes. The sashes rotate inward on their pivots for easy cleaning from inside the room, which is particularly valuable on upper floors.

What’s a Mock Sash Horn window?

A Liniar-specific product — it’s a casement-style window that reads as a sash from the outside thanks to sash horn detailing and a mid-rail. Because it operates as a casement (outward-opening), it’s cheaper, more thermally efficient, and easier to clean than a true sliding sash. Good compromise for projects where street-view authenticity matters but budget is tight.

How much does a uPVC sash window cost compared to timber?

Modern uPVC sash windows are typically 30–50% cheaper than equivalent timber sashes, and require virtually zero ongoing maintenance (no stripping, priming, painting every 5–7 years). Over a 25-year horizon, the total cost-of-ownership advantage is substantial.

Are sash windows secure?

Yes. Modern sashes include multi-point locking, sash restrictors and anti-lift devices as standard. Liniar VSS is Secured by Design accredited. Security upgrades for Approved Document Q compliance are available on all three systems.

Do sash windows meet Part L building regulations?

Yes. REHAU Heritage at 1.2 W/m²K comfortably beats the 1.6 W/m²K Part L threshold. Smart VS 600 at 1.6 W/m²K meets the threshold. Triple glazing is available on all three systems for applications targeting lower U-values.

Ready to specify?

Request a quote for sash windows — our team can advise on profile system, sash proportions, period-correct detailing, glazing options and planning-officer requirements for conservation-area installations.