Internal Wall Insulation Cost UK 2026

Internal wall insulation (IWI) is the alternative when EWI isn't possible — typically £60–£110/m² installed. Best for solid-wall pre-1920 homes. Reduces room size by 80–120 mm per wall.

Quick answer

Typical UK price range: £800–£2,500. Typical time: 2–5 days per room.

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Insulation calculator

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Insulation type Loft insulation (270mm) Cavity wall insulation External wall insulation Internal wall insulation Spray foam loft (open-cell)

Area to insulate (m²)

Region London South East South West Midlands North of England Scotland Wales Northern Ireland

Specification level Basic / standard Mid-range Premium / high-end

Extras

Pre-install survey £80–£200 Vapour control layer £150–£400 Ventilation upgrade £200–£600

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Budget Under £5,000 £5,000 – £15,000 £15,000 – £30,000 £30,000 – £60,000 £60,000+ Not sure

Timeline As soon as possible 1 – 3 months 3 – 6 months 6+ months Just researching

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Key points

• £60–£110/m² of wall
• £800–£2,500 per room
• Reduces room size by 80–120 mm
• Best for solid-wall homes where EWI isn't allowed

Cost breakdown

Item	Low	High
Insulated plasterboard	£40	£80
Fitting + finish	£20	£40
Re-piping + electrics	£300	£800
Skirting + reveals	£200	£500

Cost by UK region

Region	Typical cost
London	£2,227
South East	£2,062
South West	£1,815
Midlands	£1,650
North England	£1,485
Scotland	£1,567
Wales	£1,485

How to save money

• Always include a vapour control layer
• Plan electrics/radiators before insulating
• Use insulated plasterboard (Kingspan K17) for thinnest install

How to find a trusted tradesperson

Get at least 3 quotes from vetted UK trade networks:

• Checkatrade
• MyBuilder
• Bark

FAQs

How much room space does IWI take?

Typically 80–120 mm off each insulated wall, depending on insulation type and thickness.

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Disclaimer: Prices are guide ranges based on 2026 UK market data. Get quotes from local tradespeople for accurate pricing.