Window Installation Pricing Guide UK — Double Glazing, uPVC and Aluminium Window Costs (2026)

Overview: The UK Window Replacement Market

Over 6 million windows are replaced in the UK every year — a mix of domestic single-house jobs, flat and apartment refurbishments, and commercial work on offices, schools, and care homes. It is one of the largest recurring markets in the construction trades, driven by ageing stock, energy-efficiency upgrades, and homeowners who simply want a better-looking or more secure product.

Pricing varies more than almost any other trade sector. A standard uPVC casement supply-and-fit can sit at £350 per window; an aluminium Crittall-style unit in a period conversion can exceed £4,000 per opening. Frame material, glazing specification, window size, floor level, access, and fitting complexity all play a role. Understanding where your own work sits on that spectrum — and communicating it clearly in your quotes — is what separates busy, profitable window installers from those who are always chasing the wrong type of job.

uPVC Window Costs

uPVC remains the dominant frame material for domestic window replacement in the UK, accounting for the majority of residential installations. It is the most affordable option and the easiest to maintain.

• Standard casement window (supply and fit): £300–£600 per window for a typical 1,000 × 1,200 mm opening on a ground or first floor with straightforward access. This range reflects profile quality, hardware grade, and glass specification.
• Bay window (supply and fit): £800–£2,000 per unit, depending on whether it is a flat or canted bay, the number of lights, and whether the structural cill and lintel are in good condition.
• uPVC bifold windows (supply and fit): £1,500–£3,000 per unit for a standard two- or three-panel configuration opening onto a garden or balcony.

Within the uPVC range, price is mainly driven by four factors: profile quality (budget systems vs. premium 70 mm or 76 mm profiles with better insulation values); hardware grade (friction stays, handles, and shootbolt locking); glass specification (standard 4/16/4 air-filled units vs. 4/20/4 argon-filled with a warm-edge spacer bar); and energy rating (A++ rated windows carry a significant materials premium over A-rated units). For supply-and-fit work, these differences compound quickly across a whole-house job.

Aluminium Window Costs

Aluminium has gained significant market share in the past decade, particularly for contemporary new builds, extensions, and commercial premises. Slimmer sightlines, longer lifespan, and compatibility with high-performance glazing units make it the premium domestic choice.

• Aluminium casement window (supply and fit): £600–£1,200 per window. The wide range reflects glazing specification and whether the frame uses a thermally broken profile — a critical distinction for energy performance.
• Aluminium bifold doors (supply and fit): £2,000–£5,000 per unit for a standard three- or four-panel set. Larger spans and higher glass specifications push this well above the top of that range.
• Aluminium sliding sash (supply and fit): £800–£1,500 per window — popular for period properties seeking a low-maintenance alternative to timber with a slimmer sightline than uPVC sash.
• Crittall-style steel-look aluminium windows (supply and fit): £1,500–£4,000 per window depending on size and whether the frame is a genuine steel system or an aluminium equivalent. These are heavily in demand for orangeries, garden rooms, and internal glazed partitions as well as external windows.

Aluminium costs more than uPVC for three structural reasons: the profiles are precision-extruded with tighter tolerances; thermally broken frames require a polyamide bridge between the inner and outer skins to prevent cold bridging; and the glazing units specified are almost always higher performance (triple glazing or low-E argon-filled) than the standard domestic double-glazed unit.

Timber Window Costs

Timber remains the preferred material for period properties, conservation areas, and listed buildings — partly for aesthetic reasons and partly because planning authorities often require it. It carries a higher price point and requires more ongoing maintenance than uPVC or aluminium.

• Softwood casement window (supply and fit): £400–£800 per window. Pine and Scots softwood systems are the entry point for timber; they need painting or staining every five to seven years.
• Hardwood casement window (supply and fit): £800–£1,500 per window. Accoya, oak, and iroko are the common choices; they are more dimensionally stable than softwood and carry longer manufacturer warranties.
• New timber sash windows (supply and fit): £1,000–£2,500 per sash window, depending on size, glass specification, and whether the weights or spring-balance system is required.
• Draught-proofing and restoration of existing sash windows: £500–£900 per window. This is a distinct market from replacement — many period homeowners prefer to restore the original frames rather than replace them. The work involves removing sashes, re-cording or re-balancing, fitting brush draught seals, and re-glazing if the original glass is broken.

FENSA Certification

Window and door replacement falls under Building Regulations in England and Wales. The primary relevant documents are:

• Approved Document L1B (conservation of fuel and power in existing dwellings) — sets minimum thermal performance requirements for replacement windows, expressed as a U-value of 1.4 W/m²K or better for the whole window.
• Approved Document N (glazing in buildings) — requires safety glass in critical locations (Zone 1 and Zone 2 areas within 800 mm of floor level and 300 mm of a door).
• Approved Document F (ventilation) — replacement windows must not reduce background ventilation below the levels required; trickle vents are typically required unless the existing provision can be demonstrated to be adequate.

FENSA (the Fenestration Self-Assessment Scheme) allows registered installers to self-certify that their installation meets Building Regulations without notifying the local authority building control. This is the standard route for domestic replacement glazing throughout England and Wales.

FENSA membership costs approximately £200–£500 per year in annual fees, with an additional per-installation registration fee (typically £15–£35 per job) passed on to the customer. The FENSA certificate is issued directly to the homeowner and is required by conveyancers when the property is sold. Missing certificates routinely hold up house sales.

Other Window Certification Schemes

FENSA is not the only competent person scheme for window installation. The main alternatives are:

• CERTASS: The Certification and Self-Assessment Scheme — directly comparable to FENSA in scope and function. Some installers prefer it because the administration is simpler and the fee structure suits lower-volume operations. CERTASS and FENSA certificates carry equal legal weight for conveyancing purposes.
• BSI Kitemark: A product certification mark rather than an installer scheme — it applies to the window unit itself and confirms that it has been manufactured to BS EN standards. Useful for demonstrating product quality on commercial tenders, but does not replace FENSA or CERTASS for compliance self-certification.
• Network VEKA: A manufacturer-backed installer network for VEKA profile systems. Membership involves training and regular auditing; in return, members can offer extended manufacturer-backed guarantees (up to 10 years on frames). Useful if you are competing on quality in the mid-to-premium domestic market.

For most domestic window installers, the choice is simply FENSA or CERTASS. Both are accepted by building control authorities and by conveyancers. The practical difference is administrative: FENSA has a larger installer base and wider recognition among homeowners. If you are new to the market, FENSA membership signals credibility more readily than CERTASS, though either will do the job.

Labour-Only Window Installation Rates

Some installers work labour-only — fitting windows and doors supplied by the customer or their own chosen supplier. Labour-only rates for 2026:

• Standard casement or tilt-and-turn window (fit only): £75–£150 per window for a ground- or first-floor replacement with standard access and a clean reveal.
• Complex sizes or upper-floor access: Add 30–50% to the base rate. A third-floor window without scaffold can take twice as long and carries additional working-at-height risk that should be reflected in the price.
• Day rate (labour only): £180–£250 per day for a competent sole trader; £300–£450 for a two-person team.

Liability risk when fitting client-supplied windows: If a glass unit breaks during installation, or a sealed unit fails and mists up within a year, the question of who is responsible depends entirely on whether you supplied the unit or merely fitted it. For labour-only work, your exposure is to installation defects only — not product defects. Make this explicit in your quote and your contract: state that you accept no liability for the performance of client-supplied materials, and inspect every unit before fitting. If a unit arrives damaged or appears to be incorrectly specified, refuse to fit it and document your refusal in writing.

Window Glass Specifications

Glass specification is the most common area where customers do not fully understand what they are buying. Understanding the differences helps you justify your pricing and avoid complaints later.

• Standard double glazing (4/16/4 air-filled): Two 4 mm panes with a 16 mm air gap. Typical whole-window U-value around 2.8 W/m²K — acceptable for older properties but below current Building Regulations requirements for replacement windows.
• Low-E coating: A microscopically thin metallic oxide coating on the inner pane that reflects long-wave heat radiation back into the room. Reduces U-value to around 1.6–1.8 W/m²K on a standard 4/16/4 unit and is standard on all compliant replacement windows.
• Argon-filled cavities: Argon gas has lower thermal conductivity than air. A 4/16/4 argon unit with low-E coating achieves around 1.4 W/m²K (the current Building Regulations minimum). A 4/20/4 argon unit drops further — typically 1.2 W/m²K or better. The wider cavity adds cost to the unit but is worth specifying for energy-conscious customers.
• Triple glazing: Three glass panes, typically 4/12/4/12/4 or 4/14/4/14/4. Whole-window U-values of 0.8–1.0 W/m²K are achievable. The downside is weight — a triple-glazed unit is significantly heavier than double, which affects the frame specification and hardware loading. Part L of the Building Regulations does not currently mandate triple glazing for replacement windows in existing dwellings, but it is increasingly specified for new build and Passivhaus projects.
• Safety glass (BS EN 12600): Building Regulations (Approved Document N) require toughened or laminated glass in Zone 1 (within 800 mm of floor level) and Zone 2 (within 300 mm of a door edge). Fitting non-safety glass in these zones is non-compliant and creates a liability risk if anyone is injured. As a FENSA or CERTASS installer, this is your responsibility to specify correctly — not the customer's.

Planning Permission for Windows

Most replacement windows in residential dwellings are permitted development — they do not require planning permission from the local authority. However, there are important exceptions:

• Conservation areas: Replacement windows must match the appearance of the original windows in material, profile, and design. uPVC is frequently unacceptable in conservation areas where the original windows were timber. The homeowner needs to check with their local planning authority before proceeding; if they do not, any non-compliant window installation may require retrospective consent or removal.
• Listed buildings: Any window change — even like-for-like replacement — requires Listed Building Consent in addition to Building Regulations approval. This is a separate application from planning permission and is assessed on heritage impact grounds. As an installer, fitting windows in a listed building without Listed Building Consent puts both you and the owner at legal risk.
• Flats and apartments: The lease may contain covenants that restrict window changes — for example, requiring all windows in the block to match. The freeholder or managing agent's written consent may be needed even where planning permission is not required. Check before ordering.

Your responsibility as an installer is to make these checks part of your pre-quote survey process. If a customer confirms that planning is not required and turns out to be wrong, the installation may need to be reversed — which is expensive for everyone. A simple signed declaration from the customer confirming they have verified permitted development status (or obtained consent where required) provides useful protection.

Quoting Window Work

A well-structured window quote protects you against scope creep, manages customer expectations, and wins jobs on value rather than price alone.

Site survey checklist

• Window sizes including reveal depth and sub-cill condition
• Frame type and opening direction (casement, tilt-and-turn, sash, fixed)
• Drainage and weathering requirements at cill level
• Top-hung, side-hung, tilt-and-turn, or tilt-before-turn configuration for each opening
• Threshold and drainage detail for any door openings
• Lintel condition — visual inspection at minimum; specify in quote if uncertain
• Floor level and access requirements (scaffold, podium steps, MEWP)
• Planning or Listed Building Consent status confirmed by customer

What to include in your quote

• Supply of windows (itemised by unit with specification)
• Removal of existing windows and frames
• Disposal of old windows (skip, trade waste, or customer's own disposal)
• Installation including sealing, beading, and hardware adjustment
• Making good of window reveals (or explicitly exclude and note)
• FENSA or CERTASS certificate on completion
• Any access equipment arranged by you (scaffold, podium)

What to exclude explicitly

• Plaster making-good and redecorating around reveals
• Structural lintel replacement (unless surveyed and priced — note as conditional variation if lintel condition could not be confirmed at survey stage)
• Any electrical work (for electrically operated windows or integrated blinds — refer to a Part P registered electrician)
• Planning permission or Listed Building Consent applications