Summary

Heritage timber windows — sliding sash from the Georgian, Regency and Victorian periods, and traditional casements from earlier — are the largest single category of repair work for joiners in conservation areas. The economic argument for repair over replacement is overwhelming: a properly overhauled sash window will last another 60-100 years, costs 40-60% less than a like-for-like replica replacement, and retains the property's value in conservation-restricted areas where uPVC will reduce sale price by 5-10%.

The market is split into three tiers. At the bottom, jobbing handymen who replace a sash cord and re-puddy: cheap, fast, frequently damaging the window long-term. In the middle, specialist heritage joiners who spline rot, replace pulley boxes, draught-proof and re-glaze with linseed putty: the bulk of viable repair work. At the top, conservation-accredited workshops who hand-make replica sashes, weights and bronze hardware for Grade I and II* listed buildings.

Pricing heritage repair badly is a classic estimation failure because the work is variable in a way that uPVC swap-outs are not. One sash might need just a cord; the next might need a 200 mm splice in the bottom rail because rainwater has rotted the joint. You cannot reliably quote without inspecting each window. This guide gives the day rates and component prices to build your own quote per-window from a site survey.

Key Facts

Call-out and labour

Materials and components

Markup and pricing

Regulatory

Common job sizes (per window unit)

Quick Reference Table

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Job Scope Time Total per window (£)
Sash cord replacement, one cord Remove sash, replace one cord, refit 1.5-2.5 hrs £150-£280
Sash cord replacement, both cords Remove sash, both cords, ease & adjust 3-4 hrs £280-£450
Full sash overhaul (no DG) Strip, splice rot, new cords, draught-proof, re-putty, paint 1-2 days £900-£1,800
Full sash + slim DG units As above + new glazing, rebate adjustment 2-3 days £1,500-£2,800
Casement ease & adjust Plane down, new ironmongery, paint 2-3 hrs £180-£350
Casement rot splice Cut out rot, splice with matching timber, paint 4-8 hrs £350-£700
Casement full rebuild New sashes in matching profile, refit to old frame 1.5-2.5 days £900-£2,200
Box sash pulley replacement Strip linings, new pulleys, refit 3-5 hrs £280-£500
Putty re-glazing only Hack out old putty, prime, re-bed, paint 2-3 hrs £180-£320
Draught-proofing kit fit Ventrolla-style kit retro-fitted 2-4 hrs £280-£550
Replica replacement sash Hand-made matching sash, fit to existing box 2-3 days workshop + fit £800-£1,800
Full replica box sash window Frame, sashes, weights — replica build 4-8 days workshop + fit £2,800-£6,500

Detailed Guidance

Survey before quoting

Walk the site with a torch, mirror and tape measure. For each window, note:

A 6-window survey takes 30-60 minutes and lets you quote per window rather than as a lump sum. Customers value itemised quotes because they can phase the work. Lump-sum heritage quotes are routinely rejected as "we'll do them one at a time."

Lead paint and pre-1960 properties

Any timber painted before 1960 may contain lead. Sanding releases lead dust which is a controlled substance under COSHH. Use:

Add 20-40% to labour cost if lead paint is present on stripped surfaces.

Splicing rot

The technique that distinguishes a heritage joiner from a handyman. Rotten timber is cut back to sound material at a 45° scarf joint, and a new piece of matching timber is glued (waterproof PU or epoxy) and screwed in, then planed flush. Common splice locations:

Splice cost: roughly £80-£150 per splice in labour, £15-£40 in materials. A heavily rotten sash with 3-4 splices runs £400-£700 in repair time alone before any other work.

Sash cord replacement

Standard task; should take a competent joiner 1.5-2.5 hours per cord pair. Process:

  1. Remove staff bead (interior)
  2. Lift out lower sash, cut old cords
  3. Remove parting bead
  4. Lift out upper sash
  5. Open pocket pieces (cut out if painted over)
  6. Remove weights, attach new cords
  7. Refit cords through pulleys, knot to sash
  8. Reassemble, ease and balance

Cost per pair of cords replaced: £180-£280 typical. Doing both sashes at once is more efficient (£350-£500 for the pair) because the parting bead only comes out once.

Draught-proofing

The single most valuable upgrade for a sash window. Properly draught-proofed timber sashes match modern uPVC for air-tightness while retaining the original character. Brush-pile or pile carrier systems (Ventrolla, Mighton Reddiseals, Sashco Draught Excluders) fit into routed channels in the staff bead, parting bead and meeting rails.

Cost: £280-£550 per window fitted. Customer ROI is typically 5-10 years on heating savings alone, plus elimination of cold draughts that drive customers to replacement.

Slim profile double glazing

Where customer wants thermal upgrade and the window will accept it. Slim DG units (Slimlite, Histoglass, Pilkington Spacia) are 8-14 mm overall thickness and fit into rebates as little as 12 mm deep. Issues:

Not suitable for Grade I or many Grade II* listed properties (LPA refuses consent). Often acceptable on Grade II and unlisted-in-conservation-area properties.

Linseed putty re-glazing

Traditional putty has a 20-40 year life; modern oil-based putties (Multi-Purpose Putty) last 10-15 years. For heritage work, use boiled linseed oil putty (Allbäck, Bedec) which bonds chemically to primed timber and lasts longest.

Critical detail: timber rebates must be primed with linseed oil paint before puttying. Bare timber sucks oil out of the putty within months, causing failure. This is the most common single error on heritage glazing work.

Listed Building Consent practicalities

Conservation officers vary hugely. Some accept email notification of repair work; others want full applications with drawings and method statements for replacing a single sash cord. Universal advice:

  1. Speak to the conservation officer before quoting major work
  2. Get pre-application advice in writing (often free)
  3. Lodge LBC for anything that changes materials or appearance, even subtly
  4. For pure repair using identical materials, written confirmation from the LPA that consent is not required is gold dust

Working without consent on a listed building is a criminal offence under the 1990 Act with unlimited fines and possible imprisonment. The liability sits with the contractor as well as the owner.

Common mistakes when pricing

Regional variation

Red flags when quoting

Frequently Asked Questions

Is it cheaper to replace heritage windows with new replicas?

No. A full overhaul of an existing sash window typically costs 40-60% of a like-for-like hardwood replica replacement, and retains the original glass and ironmongery (a value contribution in conservation areas). Replica replacement makes sense only when the original is beyond economic repair (rot in more than 50% of timber, or fundamental design flaws).

How long does a heritage window repair last?

A properly overhauled sash with new cords, splined rot repairs, fresh putty and paint should give 25-40 years before needing the next overhaul. Draught-proofing kits last 10-15 years before brush piles wear out.

Can I claim VAT back on heritage window repairs?

For most domestic property, no — 20% VAT applies. The pre-2012 zero-rate for approved alterations to listed buildings was abolished. Some listed-places-of-worship work qualifies for grants. Always direct the customer to their accountant for confirmation.

Do I need Listed Building Consent for sash cord replacement?

In strict legal terms, yes — any alteration to a listed building requires LBC. In practice, most LPAs accept like-for-like repair without formal consent if the materials and method are appropriate. Confirm in writing with the local conservation officer before starting.

Can slim double glazing be installed in a Georgian sash?

It depends on the rebate depth (most Georgian sashes are too thin to accept slim DG without weakening the glazing bars), and the planning authority's view. Grade I and most Grade II* — refused. Grade II and unlisted-in-CA — often accepted with pre-application discussion. Always check before committing to the customer.

Regulations & Standards