House extensions across Kent

What decides the cost and the timescale

Two things set the shape of an extension project before design begins: your planning route, and the ground. Many single storey rear extensions still fall within permitted development, but conservation areas, listed buildings, Article 4 directions, flats and estate planning conditions all remove that option, and Kent has plenty of each. Establishing the route first avoids designing something that cannot be built.

The ground matters just as much. Much of the county sits on Weald clay, which shrinks and swells with moisture, so foundations are frequently deeper than people expect, especially near mature trees. Ground works and drainage are the two lines in a quote most likely to move, which is why they should be surveyed rather than assumed.

• Design and survey, with a brief that states what the room is actually for
• Planning route confirmed: lawful development certificate or a householder application
• Structural calculations, then the building regulations application
• Party wall notices where a shared wall or a neighbour's foundation zone is affected
• Build sequence: foundations and drainage, shell and roof to weathertight, then first fix, plaster and second fix
• Completion certificate from building control, which is the document a buyer will ask for

Guides

Useful House Extensions guides

• Kitchen extensions: layouts, structure and planning
• Ground floor extensions: options, planning and what to decide first
• Two storey and multi-storey extensions: planning and build
• Side return extensions explained
• Householder planning applications explained
• L-shaped extensions: is one right for your house?
• Wrap around extensions: what they are and when they make sense
• Flat roof extensions: build-ups, lanterns and avoiding leaks
• Can you lay EPDM over felt? Overlay versus strip and replace
• Property extensions: types, planning and what to expect

Across Kent

House extensions in Kent

House extensions are the bulk of our larger Kent projects — single-storey rear extensions, two-storey side returns, wrap-arounds and orangery-style glazed additions. We run design-and-build end-to-end: architectural drawings, planning application, structural calcs, building regs and the full build under one written contract.

Most Kent rear extensions sit within permitted development at up to 4m deep for a detached home and 3m for a semi/terrace. Larger schemes go through the neighbour-consultation route or full planning — both routes we submit and follow up on your behalf.

Typical Kent extension build is 14–18 weeks for a 25–35m² rear single-storey, including weather-tight shell at week 6–7 and break-through to the existing kitchen at week 10–11.