London & South-East England
External Wall Insulation (EWI)
External wall insulation wraps the outside of your home in an insulating board, then finishes it with a protective, weatherproof render. For the solid-wall Victorian, Edwardian and pre-1930s housing that dominates much of London and Kent, it is the single most effective thermal upgrade available — typically cutting wall heat loss by around 70% without losing a single centimetre of internal floor space.
Is EWI right for your home?
- Solid-wall properties (typically pre-1930s) with no cavity to fill
- Homes outside conservation areas where external changes are permitted
- Owners wanting the biggest possible thermal gain in one project
- Tired pebbledash or render façades due for refurbishment anyway
- 1930s–1960s semis where the whole house can be treated at once
External Wall Insulation: key facts
- Best for solid-wall homes (typically pre-1930s) with no cavity to fill.
- Cuts wall heat loss by around 70% and eliminates cold bridging.
- Typical cost £110–£140/m² — roughly £12,000–£22,000 for a 3-bed semi.
- Adds insulation outside, so you lose no internal floor space.
- Not suitable for most conservation areas or listed frontages — choose IWI there.
- PAS2030-19 certified, TrustMark registered, 25-year system guarantee.
What is external wall insulation?
Because the insulation sits on the outside, EWI also eliminates cold bridging, protects the original brickwork from weather, and gives tired façades a clean, modern finish. The trade-off is that it changes the external appearance, so it is not suitable for most conservation areas or listed frontages — in those cases internal wall insulation is the right call.
We are a PAS2030-19 and TrustMark certified installer and fit manufacturer-approved systems end to end with our own trained team — no subcontractors. Every quote is free, fixed and itemised, with a written specification you can rely on.
External Wall Insulation cost guide
Indicative 2026 pricing for London & the South-East, based on hundreds of real quotes and 500+ completed installations — not generic industry averages. Every quote is free, fixed and itemised, with no hidden extras.
| Job type | Indicative cost |
|---|---|
| Mid-terrace (rear/side elevations) | £8,000 – £14,000 |
| Typical 3-bed semi-detached | £12,000 – £22,000 |
| Detached house | £18,000 – £30,000+ |
| Per m² (system + render + labour) | £110 – £140 / m² |
What real jobs actually cost
Anonymised prices from recent jobs our own team won and installed across London and the South-East. Every home differs — your fixed, itemised quote follows a free survey.
| When | Area | Work | Size | Price |
|---|---|---|---|---|
| April 2026 | Worcester Park (KT4) | External wall insulation | 58 m² | £13,352£232/m² |
| March 2026 | South Norwood (SE25) | External wall insulation | 62 m² | £12,600£202/m² |
| January 2026 | Ruislip (HA4) | External wall insulation | 102 m² | £17,898£176/m² |
| October 2025 | Kingston upon Thames (KT2) | External wall insulation | 90 m² | £19,520£216/m² |
| June 2025 | High Wycombe (HP11) | External wall insulation | — | £23,350 |
| April 2025 | Raynes Park (SW20) | External wall insulation | — | £22,130 |
| January 2025 | Worcester Park (KT4) | External wall insulation | — | £19,180 |
| January 2025 | Tooting (SW17) | External wall insulation | — | £3,800 |
Prices are real totals paid for the specific scope of each job (access, condition and finishes vary) — use them as honest reference points, not like-for-like quotes. Full cost guide
Recent EWI work
Real jobs completed by our own team across London and the South-East.
90mm EPS External Wall Insulation
External wall insulation in Harrow
Brick Slips
Brick slip installation instead of render
External Wall Insulation
Finished Install in SW London
Systems & materials we install
How EWI installation works
Free survey
We assess wall construction, check for damp, measure up and confirm whether EWI is the right specification for your property.
Specification & quote
A fixed written quote within 24 hours, including board type, render finish, scaffolding and making good.
Installation
Scaffold up, boards mechanically fixed and bonded, beads and mesh set, then base coat and decorative render applied by our own team.
Sign-off & guarantee
Final inspection, TrustMark lodgement, and a manufacturer-backed system guarantee (typically 25 years).
Free survey & fixed quote
Book a free, no-obligation survey and we'll send a clear, fixed written quote within 24 hours — PAS2030-19 certified and TrustMark registered, with all work installed by our own trained team.
Get a free quoteExternal Wall Insulation FAQs
How much does external wall insulation cost?
Do I need planning permission for EWI?
Will EWI cause damp?
How long does it take?
How much will it save on heating bills?
Areas we cover
We install external wall insulation across London and the South-East. See all areas we cover →
Other insulation services
Deciding between the two? Compare external vs internal wall insulation →
Related guides
In-depth, independent guidance to help you decide.
Last reviewed June 2026 by Stay Warm Insulation.
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