Extending a home in Royal Greenwich? 2026 costs per m², permitted development rules, conservation areas and where Article 4 directions restrict works.

Extending a home in Lewisham? 2026 costs per m², when you need planning permission, and how Article 4 rules in Blackheath, Brockley and Telegraph Hill work.

Extending a home in Southwark? 2026 costs per m², the borough's 48 conservation areas, the Sunray Estate Article 4 and the Dulwich Estate rules, explained.

Extending a home in Lambeth? 2026 costs per m², when you need planning permission, conservation area and Article 4 rules, and the council's design guidance.

Extending a home in Merton? 2026 costs per m², when you need planning permission, and how the John Innes Article 4 rules in Merton Park actually work.

Extending a home in Kingston upon Thames? 2026 costs per m², when you need planning permission, conservation area rules and the council's design guidance.

Extending a home in Richmond upon Thames? 2026 costs per m², 72 conservation areas, street-level Article 4 Directions and permitted development, explained.

Studio MASS works with homeowners across London, and we are publishing a planning and cost guide for every borough we serve. Each guide answers the same three questions: whether you need planning permission, what an extension realistically costs in 2026, and what a well-run project involves from first idea to finished build. The guides published so far: Home extension design in Haringey Home extension design in Camden Home extension design in Barnet Home extension design in H

Extending a home in Harrow? 2026 costs per m², when you need planning permission, plus conservation area and Article 4 rules in Pinner and Harrow on the Hill.

Extending a home in Brent? 2026 costs per m², permitted development rules, and why all 22 conservation areas carry Article 4 Directions. Honest guidance.

Extending a home in Ealing? 2026 costs per m², conservation area and Article 4 rules in Brentham and Hanger Hill, and what planning will realistically allow.

Extending a home in Hackney? 2026 costs per m², permitted development rules, conservation areas and the new Article 4 Directions that took effect in 2025.

Extending a home in Islington? 2026 costs per m², permitted development rules, the 42 conservation areas and what Article 4 Directions mean for your street.

Extending a home in Camden? 2026 costs per m², permitted development rules, conservation area Article 4 Directions and the borough-wide basement rule.

Before you extend or renovate a London home, a fixed-fee feasibility review shows what is achievable, what planning will allow, and what it will really cost. Here is a real example, and why £450 can save £45,000.

Extending a home in Enfield? 2026 costs per m², permitted development rules, the 22 conservation areas and which ones carry Article 4 Directions.

Extending a home in Barnet? 2026 costs per m², permitted development rules, the 16 conservation areas and why Hampstead Garden Suburb plays by its own rules.

Extending a home in Wandsworth? 2026 costs per m², conservation area and Article 4 rules, basement guidance, and a real Tooting basement and whole-house project.

Extending a home in Haringey? 2026 costs per m², when you need planning permission, conservation area rules, and a real Hornsey project built for £140,000.

Progress update on our kitchen extension project: glazed roof, garden access, modern kitchen, and a complete bathroom renovation.