Two-storey rear or side extensions adding kitchen/dining downstairs and a master bedroom or en-suite above — typically 40–60 m² of additional space.
Double-storey extensions in Stevenage typically cost between £74,918 and £120,780 depending on size, specification and site conditions. A mid-range 50 m² project averages around £97,751.
Most double-storey extensions take between 6 and 16 weeks on site, depending on scope, structural complexity and planning requirements in East of England.
Many double-storey extensions fall under permitted development, but conservation areas, listed buildings and larger projects in Stevenage can require a full planning application. Use the cost checker to see what applies to your address.
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Disclaimer: This is an industry-informed estimate for guidance only — not a fixed quote, valuation, survey or legal advice. Figures are based on UK regional averages and the details you provided. Site-specific factors (access, ground conditions, structural surprises, planning constraints) can materially change the cost. Always confirm with a site inspection, written quotes from qualified UK tradespeople, and supplier pricing before committing to work. Build Price IQ accepts no liability for decisions made on the basis of these estimates.