Choosing the right window style affects your home’s appearance, energy performance, ease of cleaning, and ventilation. The most common types in UK homes — casement, sash, tilt-and-turn, and bay — each suit different building types and uses. Prices range from around £300 per casement unit to over £2,000 for a bespoke timber sash, supply and fit.
Casement Windows
The default choice for most UK new-build and replacement projects. A casement window has one or more panes hinged at the side (or top, when called an awning or top-hung casement) and opens outward on a friction-stay hinge. Most modern casements are side-hung; a fixed pane can sit beside the opening sash.
Best for: post-war housing, new builds, contemporary homes, and any property where cleaning and ventilation take priority over period aesthetics.
Casement subtypes
- Side-hung casement — opens from a side hinge; the most common UK type.
- Top-hung casement — hinged at the top; opens outward from the bottom; ideal for restricted ceiling heights or rooms where full reach to the handle is difficult.
- French casement — paired doors (no centre post); wide opening but reduced draught-proofing unless fitted with espagnolette locks.
- Tilt-before-turn (tilt-first) — see tilt-and-turn section below.
Typical cost (supply & fit): £300–£900 per unit in uPVC; £500–£1,400 in aluminium; £700–£2,000 in timber.
Sash Windows
Sash windows are the defining feature of Georgian, Victorian, and Edwardian terraces. Two sashes (frames) slide vertically in channels — traditionally counterbalanced by lead weights on cords; modern versions use spiral balances or constant-force springs.
Best for: period properties (pre-1920 housing), conservation areas, listed buildings, and anywhere the streetscape character depends on the original window style.
Box sash vs. spring-balanced
- Box sash (weights): traditional timber frame with a hollow box housing cast-iron or lead weights. Authentic for listed and conservation-area properties; requires specialist joinery skills to maintain.
- Spring-balanced sash: thinner frame, easier to manufacture in uPVC or aluminium; suitable for most period replacement projects where full authenticity isn’t essential.
Tilt-clean facility
Most modern sash windows allow the sashes to tilt inward for cleaning — an important feature if the window is above ground-floor level.
Typical cost (supply & fit):
- uPVC spring-balanced sash: £600–£1,200 per unit
- Aluminium sash: £900–£1,800 per unit
- Timber box sash (restoration): £1,500–£3,500+ per unit
Tilt-and-Turn Windows
Popular in continental Europe and increasingly common in the UK, tilt-and-turn windows open in two ways: tilt inward from the top for background ventilation (common in the UK as “secure ventilation”), or swing inward fully from the side for cleaning and maximum airflow.
Best for: upper-floor rooms, flats (where outward opening risks passers-by), and any space where cleaning access is difficult from outside.
- Security advantage: the tilt position provides ventilation without creating a climbable opening — suitable for ground-floor use while you’re in the room.
- Cleaning: the inward-opening action makes window cleaning straightforward from inside.
- Draught performance: European-standard compression seals give better draught and acoustic performance than friction-stay casements.
Typical cost (supply & fit): £400–£1,000 per unit in uPVC; £700–£1,600 in aluminium.
Bay Windows
A bay projects outward from the main wall in three or more planes. Structural bays require a lintel or corbelled brickwork; shallow bow windows curve in a gentle arc. Common in Victorian semis and detached houses of the Edwardian and interwar periods.
- Bay windows are usually a combination of fixed and opening casements or sashes.
- Replacement requires careful measurement of the angle at each corner (typically 90°, 135°, or 120°).
- Structural implications (lintel condition, foundation depth) must be assessed before replacement.
Typical cost (supply & fit): £1,200–£4,000 for a standard three-section bay in uPVC; significantly more for aluminium or timber.
Fixed Windows (Picture Windows)
Non-opening panes used where ventilation is provided elsewhere. Offer maximum thermal performance (no seal gaps around the opener) and maximum glazing area. Common above large sliding or bi-fold door systems.
Typical cost (supply & fit): £200–£600 per unit in uPVC.
Window Style Comparison Table
| Style | Opens? | Best application | Period match | Relative cost |
|---|---|---|---|---|
| Side-hung casement | Outward (side) | General-purpose | Post-war, new-build | Low–medium |
| Top-hung casement | Outward (top) | High openings, tight spaces | Modern | Low–medium |
| Vertical sliding sash | Vertical slide | Victorian/Edwardian terraces | Victorian, Edwardian, Georgian | Medium–high |
| Tilt-and-turn | Inward (tilt or full turn) | Flats, upper floors, cleaning | Contemporary, European-style | Medium |
| Bay/bow | Various | Victorian semis, Edwardian | Victorian, Edwardian | High |
| Fixed (picture) | No | Light-only locations | Any | Low |
Materials
uPVC — the market leader for replacement windows. Low maintenance, thermally efficient, and competitively priced. Profile quality varies: look for multi-chambered sections and at least a 28 mm double-glazed unit; triple-glazed units are worth specifying in north-facing or exposed locations.
Aluminium — slim sightlines, any RAL colour, 40+ year lifespan. Thermally broken frames are essential to prevent cold bridging; U-values of 1.2–1.6 W/m²K are achievable. Higher cost than uPVC but increasingly chosen for contemporary properties.
Timber — the only appropriate choice for listed buildings and many conservation-area properties. Softwood (pine, redwood) is cheaper; hardwood (oak, accoya, meranti) is more durable. Requires painting or staining every 5–10 years. Modern engineered timber (accoya treated with acetic anhydride) offers exceptional dimensional stability and a 50-year warranty against rot.
Timber-aluminium composite — timber internally (for warmth and aesthetics), aluminium cladding externally (for weather resistance). Premium product; common in Scandinavian-specification builds.
Glazing Specifications
Under Part L of the Building Regulations (England), replacement windows in existing dwellings must achieve a whole-window U-value of 1.4 W/m²K or better (or a window energy rating of Band C minimum).
- Double-glazed (4/16/4 with argon, low-e coating): U-value around 1.2–1.4 W/m²K — meets regs.
- Triple-glazed (4/16/4/16/4): U-value 0.7–1.0 W/m²K — worth specifying for north-facing rooms, noise-sensitive locations, or Passivhaus-standard projects.
- Acoustic glazing: asymmetric panes (e.g. 6/12/10) reduce sound transmission; relevant for roads above 60 dB.
Choosing the Right Style
- Match the original style where possible — a Victorian terrace looks wrong with tilt-and-turn. Check if you’re in a conservation area (special conditions apply).
- Consider first-floor cleaning access — tilt-and-turn or top-hung casements save the cost of hiring a window cleaner.
- Ventilation requirements — the Building Regulations require background ventilation in habitable rooms; trickle vents in the frame or head are the most common solution.
- Budget — uPVC casements are the most affordable; timber sashes the most expensive. Aluminium offers a strong mid-to-premium option.
- Conservation area or listed building? — consult your local planning authority before ordering; timber vertical sliders in the original style are often required.
