Question 1

How much does a full-width single-storey rear extension cost in Harpenden, AL5?

Accepted Answer

A full-width single-storey rear extension on an Edwardian or interwar detached house in AL5 — covering the structural shell, groundworks, roof, glazing and a fully fitted kitchen — typically runs between £75,000 and £145,000. The depth and total footprint of the extension, the roof treatment (flat with rooflights, lantern, or pitched), and the kitchen specification are the biggest variables. Two-storey or wrap-around additions sit above that range. We present the build structure and the kitchen fit-out as separate cost lines on the quote so the split is transparent before you decide.

Question 2

Does permitted development cover rear extensions and loft conversions in Harpenden, AL5?

Accepted Answer

Many of the large detached plots across AL5 do fall within St Albans City and District Council's standard permitted development envelope for single-storey rear extensions, so a planning application is not automatically required. Larger two-storey rear additions and the majority of side extensions will need a full application regardless of plot size. Green Belt land runs to the east of the town, but that designation restricts new freestanding buildings rather than extensions to existing homes — so most established AL5 properties are unaffected for extension purposes. We confirm what applies to your specific address during the site visit before recommending the planning route.

Question 3

What does a combined rear extension, loft conversion and whole-house renovation cost in Harpenden?

Accepted Answer

Combining all three scopes on a large Edwardian or interwar house in AL5 generally lands between £160,000 and £280,000, depending on the size of the extension and loft, the level of internal reconfiguration, and the kitchen and bathroom specifications. Packaging everything under one contract means trades can overlap efficiently and the house is only disrupted once rather than twice or three times. Where the programme includes a boiler replacement or new central-heating layout, that element is carried out by our Gas Safe registered partner, scheduled within the same build programme. We are fully insured and the quote itemises each phase before work begins.

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Commonquestions, Harpenden.

Let's talk through what you're planning.