01
Budget one, the shell
Foundations, walls, roof, glazing, the structural opening into the existing house, drainage and weather-tightness. This is the part that can be drawn, specified and priced accurately, and it should be settled first.
Cost guide · Cornwall
Kitchen extension costs in Cornwall, two budgets that keep getting confused
A kitchen extension is the project where budgets most often drift, and the reason is structural rather than behavioural. There are two separate budgets, the shell and the fit out, and they are usually decided by different people at different times, one from drawings and one in a showroom.
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02
Budget two, the fit out
Units, worktops, appliances, flooring, lighting, tiling and decoration. This is where the range is enormous, because the same room can be finished at three very different levels without a single line on the drawing changing.
- Units and worktops, where the spread between ranges is larger than most people expect
- Appliances, particularly where extraction has to be ducted through an external wall
- Flooring, especially if underfloor heating is going in and the build-up has to allow for it
- Lighting and electrics, which need designing around the layout rather than added at the end
03
Drainage decides more than you think
Where the existing soil and waste runs sit will influence where the sink, dishwasher and any new WC can reasonably go. We record drainage during the measured survey so the layout is designed around it rather than fighting it later at extra cost.
04
Coordinating with your kitchen supplier
The most avoidable cost on a kitchen extension is remedial electrical and plumbing work because the unit layout changed after first fix. We coordinate the supplier's layout onto the construction drawings so services land in the right places the first time.
Frequently asked
Straight answers.
- Why do kitchen extension quotes vary so much?
- Because some include the fit out and some do not. Establish which budget each quote is covering before comparing them.
- Does moving the kitchen to the new space cost more?
- It usually means extending drainage and services, which has a cost, but it often produces a far better plan. It is worth pricing both options rather than assuming.
- Do I need building regulations approval for a kitchen extension?
- Yes. Structure, insulation, ventilation, drainage and electrical work are all covered, and the completion certificate is what a buyer's solicitor will ask for later.
- Can you build it as well as design it?
- Yes. We are a design and build studio, so the drawings and the site work come from the same team, which is unusual and is exactly where the coordination problems disappear.
Read next
- Single storey extension costs in Cornwall, where the money actually goes
What a single storey extension really costs in Cornwall and what moves the number: ground, glazing, access and roof tie-in. Free first consultation, design and build.
- Building an extension in Cornwall: the steps in order
Every stage of a Cornwall extension in the order it happens, from first consultation and survey through planning, building regulations, tender and completion certificate.
- Knock-throughs and structural alterations
Removing walls, forming openings and opening up Cornish houses — structural calculations, building notices and drawings that let a builder price the work properly.
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