How to Price Secondary Glazing: Labour, Materials and Margin Guide

Quick Answer: Secondary glazing typically runs £250–£600 per window for standard sliding or lift-out units supplied and fitted, £600–£1,200 for larger or acoustic units, and £1,000–£2,500+ for bespoke heritage or curved frames. Fitting labour is fast — most units are 1–2 per fitter per hour for off-the-shelf, or 30–60 minutes each including making good — so the headline rate is the £180–£280 per fitter per day plus the unit cost. Crucially, secondary glazing does not normally need Building Regulations or FENSA, which removes a cost and approval step that replacement windows carry.

Summary

Secondary glazing is an independent internal glazed system fitted to the room side of an existing window, leaving the original window in place. That single architectural fact is the whole commercial story: because you're not removing or replacing the primary window, the work falls outside FENSA and the replacement-window route of Building Regulations Part L/F that double glazing triggers. There's no certificate to buy, no notification, and on listed buildings and in conservation areas it usually avoids the consent battle that swapping the original windows would start. For the tradesperson that means a faster, lower-friction job — and for the customer a cheaper route to warmth and quiet, which is the pitch that sells it.

The work is essentially measure, supply and fit. Units are made to size (off-the-shelf ranges or bespoke), delivered, and screwed to a sub-frame or directly into the reveal with brush or compression seals. There's minimal wet trades, minimal disruption, and the labour is quick relative to the unit cost — which means materials (the units) are the dominant share of the price, the inverse of most repair work. Net margin is built into the unit markup and a sensible fitting rate, not into long labour hours.

For pricing validation: the three things that move the price are unit type (fixed/lift-out vs sliding vs hinged vs vertical sliding sash to match a sash window), glass spec (standard 4mm vs acoustic laminate for noise, or low-E for thermal), and size and bespoke shaping (square off-the-shelf is cheap; arched, curved or oversized heritage units are not). Access is rarely the cost driver it is on roof and chimney work because secondary glazing is fitted from inside — the red flags here are awkward reveals, listed-building detailing and matching sightlines, not scaffolding.

Key Facts

• Fitter day rate — £180–£280 per person per day; £250–£350 in London and the South East.
• Fitting time — 30–60 minutes per standard unit including making good; a houseful is often a 1–2 day job for one or two fitters.
• Standard sliding unit (supplied + fitted) — £250–£600 per window.
• Lift-out / fixed unit — £180–£450 per window (cheapest type).
• Hinged / side-hung unit — £300–£650 per window.
• Vertical sliding (sash-matching) unit — £400–£900 per window.
• Acoustic unit (laminated glass, wider air gap) — £600–£1,200 per window.
• Bespoke / heritage / curved unit — £1,000–£2,500+ per window.
• Glass — standard 4mm float — included in base unit price.
• Glass — acoustic laminate (6.4mm+) — adds £80–£250 per unit.
• Glass — low-E thermal — adds £40–£120 per unit.
• Air gap for acoustic performance — 100–200mm gap gives the best noise reduction (vs the 12–16mm of a sealed double-glazed unit).
• Air gap for thermal performance — 20mm+ improves U-value; smaller gaps still help.
• Materials share — 55–75% of total (units dominate; labour is light).
• Net margin — 25–40% achievable via unit markup plus a fair fitting rate.
• No FENSA / Building Regs notification — secondary glazing is not replacement glazing, so it's outside the FENSA scheme.
• Listed buildings / conservation areas — usually avoids the consent issue that replacing original windows triggers; still check with the local conservation officer.
• MEES / EPC — secondary glazing improves U-value and can lift an EPC rating, useful for landlords meeting MEES.
• Acoustic benefit — well-fitted secondary glazing with a wide air gap can cut noise by 40–50dB; reference BS 8233 for sound insulation in buildings.
• VAT — standard 20% on most domestic work.

Quick Reference Table

Detailed Guidance

Labour time

Secondary glazing is the rare job where labour is the small number. Off-the-shelf units fit in 30–60 minutes each including making good and sealing — a fitter can do a houseful of 8–12 standard windows in one to two days. Bespoke and heritage units take longer to fit (closer sightline tolerances, scribing to out-of-square reveals) but still measured in tens of minutes, not hours. The labour cost on a typical job is one to two fitter-days; the rest is the units.

The time that's easy to under-count is the survey and measure. Secondary glazing has to fit the existing reveal exactly, and old buildings are rarely square. A careful measure prevents the expensive mistake of a unit that won't fit — either absorb the survey into the quote or charge a small fee credited against the order.

Materials and 2026 prices

Units are the dominant cost and are priced by type, size and glass spec. As a 2026 supply guide per unit:

• Lift-out / fixed — £120–£300; simplest, often magnetic or clip-in, cheapest to make and fit.
• Horizontal sliding — £150–£400; the everyday workhorse.
• Hinged / side-hung — £200–£450; where the customer needs to open it for ventilation or cleaning.
• Vertical sliding — £280–£650; matches the operation of a sash window, the right choice on a period property.
• Glass upgrades — acoustic laminate adds £80–£250 per unit; low-E thermal glass adds £40–£120.
• Bespoke shaping — arched, curved or oversized units £700–£1,800+ per unit.
• Sundries — sub-frames, brush/compression seals, screws and trims; a small per-window spend.

Mark up the units at your standard rate — this is where the margin lives, because the labour is light. Buy from a trade-account supplier; the retail-vs-trade gap on secondary glazing units is significant.

Access and survey (not the usual red flag)

Because secondary glazing is fitted from inside the room, the scaffolding cost that dominates roof and chimney work doesn't apply. Access is rarely a price driver. What replaces it as the risk is the reveal and the detailing:

• Out-of-square reveals in old buildings mean scribing or packing; survey carefully.
• Deep or shallow reveals affect the air gap you can achieve — and the air gap is what delivers the acoustic and thermal benefit you're selling.
• Listed and conservation properties need sightlines and finishes that don't visually clash with the original window; this is a selling point of secondary glazing (it's reversible and non-destructive) but the detailing must be right.

Itemise a survey visit if the property is awkward, and never quote a bespoke unit off the customer's own measurements.

Regional rates

Fitting is light, so regional variation hits the day rate rather than the unit price (units are bought from regional or national suppliers at broadly similar trade prices). As a 2026 per-fitter day-rate guide:

• London and South East — £250–£350
• South West, East, Midlands — £200–£280
• North of England — £180–£250
• Scotland, Wales, Northern Ireland — £170–£250

Margin

A net margin of 25–40% is realistic. The structure is the inverse of repair trades: materials (units) are 55–75% of the price, labour is light. That means your margin is driven by the markup you put on the units and a fair, not padded, fitting rate. The mistake is competing on the unit price against an online-only seller — sell the fitted, surveyed, guaranteed package and the no-FENSA, no-consent advantage, not a box of glass.

When secondary glazing wins the job over double glazing

This is the pitch that converts, and it's worth a tradesperson understanding it to quote confidently:

• Listed buildings and conservation areas — replacing original windows usually needs listed-building or planning consent and may be refused. Secondary glazing is internal, reversible and typically avoids the consent issue entirely.
• No FENSA / no Building Regs notification — you're not replacing glazing, so the FENSA route and Part L thermal-replacement obligations don't apply, which removes cost, paperwork and time.
• Acoustic performance — a wide air gap (100–200mm) outperforms a sealed double-glazed unit for noise, often by 40–50dB; reference BS 8233 for sound insulation targets. This is the strongest selling point on busy roads and flight paths.
• MEES / EPC — landlords needing to meet Minimum Energy Efficiency Standards can use secondary glazing to improve the U-value and lift the EPC rating without ripping out windows.
• Cost — usually cheaper per window than replacement double glazing once the consent and FENSA costs of the alternative are counted.

Red flags and what to quote

• Customer-supplied measurements — never quote bespoke off these; survey it yourself.
• Out-of-square / non-standard reveals — price the scribing and packing.
• Air-gap expectations — if the customer wants the acoustic benefit, the reveal must allow a wide gap; manage expectations before quoting.
• Glass spec mismatch — quoting standard glass when the customer's real problem is noise (needs acoustic laminate) means an unhappy customer; ask what they're solving.
• Listed-building detailing — confirm sightlines and finishes with the conservation officer if relevant.

Itemise as: survey (if charged); units by type, size and glass spec; sub-frame and seals; fitting labour; and making good. State the glass spec and air gap so the customer can compare like-for-like.

Frequently Asked Questions

How much should I quote per window for secondary glazing?

Standard sliding units supplied and fitted are £250–£600 per window; lift-out units less, acoustic units £600–£1,200, and bespoke heritage units £1,000+. A houseful of 8–12 standard windows is typically £2,500–£6,000.

Does secondary glazing need Building Regulations or FENSA?

No, not normally. It's an additional internal system, not a replacement window, so it falls outside FENSA and the replacement-glazing route of Building Regulations. That's a genuine cost and time saving worth stating on the quote.

Why does secondary glazing win on listed buildings?

Replacing original windows usually needs listed-building or planning consent and is often refused on heritage grounds. Secondary glazing is internal, reversible and non-destructive, so it typically avoids the consent issue while still delivering warmth and noise reduction.

Is secondary glazing better than double glazing for noise?

For noise, often yes — a wide air gap (100–200mm) outperforms the narrow sealed gap of a double-glazed unit. With acoustic laminated glass it can cut noise by 40–50dB. Reference BS 8233 if the customer has a specific acoustic target.

Where does the margin come from if the labour is so quick?

From the unit markup, not the hours. Materials are 55–75% of the price, so buy on trade terms, mark up sensibly, and sell the fitted, surveyed, guaranteed package — not a bare box of glass against an online seller.

Regulations & Standards

• Building Regulations — secondary glazing exemption — secondary glazing is an additional system, not replacement glazing, so it does not trigger the FENSA route or the replacement-window thermal obligations of Approved Document L.

• FENSA — the competent-person scheme for replacement glazing; does not apply to secondary glazing because the primary window is retained.

• BS 8233 — guidance on sound insulation and noise reduction for buildings; the reference standard when selling acoustic secondary glazing.

• MEES (Minimum Energy Efficiency Standards) — minimum EPC requirements for let property; secondary glazing can contribute to an improved U-value and EPC rating.

• Listed Building Consent / conservation area controls — replacing original windows usually requires consent; secondary glazing is typically exempt as a reversible internal alteration, but confirm with the local authority conservation officer.

• Approved Document L (conservation of fuel and power) — relevant to U-value context, though secondary glazing avoids the replacement-glazing trigger.

• FENSA — what is and isn't covered — confirms secondary glazing falls outside replacement-glazing certification

• BS 8233 — sound insulation and noise reduction for buildings (BSI) — acoustic performance reference

• Historic England — secondary glazing in historic buildings — heritage and conservation guidance

• MEES / domestic private rented property minimum standard (GOV.UK) — landlord energy efficiency obligations

• Approved Document L (GOV.UK) — conservation of fuel and power, U-value context

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