How Much Does Plaster Cornice Replication Cost in London?

Yes — adding period cornice to a non-period property for character is increasingly popular but requires careful design judgement. Considerations. (1) Period authenticity — 'genuine Victorian replica' in a 1950s house is decorative pastiche; embrace this as design choice rather than aiming for archaeological accuracy. (2) Profile scale — original Victorian cornice profiles were sized for 3.0–3.5m ceiling heights; 1950s rooms often have lower ceilings (2.4–2.7m) where Victorian-scale cornice looks disproportionate. Choose modest profile (100–150mm depth) for low ceilings. (3) Ceiling structure — plasterboard ceilings can accept pre-cast cornice; fix with screws to joists + adhesive at wall junction. Cost: £55–£140 per linear m for pre-cast in a typical room (typical 24 linear m reception in a 1950s house: £1,300–£3,400). Design recommendation: keep profile simple (subtle plain Egyptian/dentil rather than ornate foliate); pair with appropriate-scale skirting board and door architrave for coherent period aesthetic.

Specialist process. (1) Measure intact cornice — specialist plasterer with profile gauge takes detailed measurements at 4–6 points along the intact cornice; records depth, width, individual feature dimensions. (2) Photograph intact cornice — high-resolution images at multiple angles for reference. (3) Draw full-size profile — based on measurements, specialist draws full-size profile on graph paper or CAD. (4) Cut template — zinc template cut to profile; verified against intact cornice (held against intact cornice and shadow inspected for match). (5) Manufacture and install. Adjacent room cornice that doesn't match (e.g. original front reception cornice + new back reception cornice — different periods because back reception was extended later) is a frequent issue. Solution: typically specialist replicates the most ornate (front reception) profile in the new room for design coherence; alternative is to specify period-appropriate but different profile in the new room (e.g. new extension can have simpler cornice consistent with Edwardian rather than Victorian).

Subtle differences visible to trained eye; minimal practical difference for typical viewer. Differences. (1) Joints — pre-cast sections have visible joints (typically 2–4mm gap between sections, filled with mortar). Located at corners and at 1.2m or 2.4m intervals along walls. Run-in-situ has no joints (continuous application). (2) Profile sharpness — pre-cast: machine-perfect mould produces uniformly sharp profile; run-in-situ: subtle hand-finished variation produces slightly more authentic appearance. (3) Material density — pre-cast: lightweight fibrous (~6kg per linear m); run-in-situ: heavier solid plaster (~12–18kg per linear m). (4) Lifecycle — both 50–100 years if correctly installed and decorated; pre-cast joints can crack from building movement (re-filled and decorated, £30–£80 per joint). For most London properties, pre-cast is the practical choice with negligible aesthetic compromise. For listed buildings and prime conservation work, run-in-situ is typically specified by conservation officer.

Gauged plaster is lime plaster mixed with a small percentage of gypsum (called 'gauging') to control setting time. Pure lime plaster (NHL 3.5 hydraulic lime + sand) sets very slowly (3–7 days for first-stage set, weeks for full strength) which is impractical for fast site programmes. Gauged plaster adds 10–25% gypsum (Thistle Multifinish or similar) which initiates set in 30–60 minutes, allowing rapid working. Once set, the lime continues to cure for months, achieving full breathability and chemical compatibility with original lime walls. Specification: 1 part NHL 3.5 hydraulic lime + 0.5–1 part gypsum + 3 parts clean sharp sand. Industry name: 'lime/gypsum gauged plaster' or 'lime-gauged finish coat'. Used for all cornice work in pre-1919 London properties. Modern proprietary alternatives include St Astier NHL Plaster and Ty-Mawr Lime Plaster systems. Critical: never specify pure gypsum plaster on lime substrate (chemical incompatibility) and never specify pure lime without gauge in time-constrained site programmes (impractical setting time).