Guide · Process
Most of the stress in an extension comes from not knowing what happens next. The sequence below is the one nearly every project follows, with the decisions that belong at each stage. Read it once and the quotes, the waiting periods and the paperwork all stop feeling random.
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A free first conversation — no obligation, no sales calls.
01
A visit to the property to talk through what you want, what the building allows and what the likely consent route is. This is where the obvious problems surface cheaply: a planning condition removing permitted development, a drain in the wrong place, a boundary that will need a party wall notice. Ours is free and carries no obligation.
02
An accurate dimensional record of the existing building. Everything drawn later relies on this being right, and in older Cornish properties it almost never matches whatever paperwork already exists.
03
Options, then a preferred scheme. This is the point to change your mind, because moving a wall on a drawing costs nothing and moving it on site costs a fortune. Budget should be discussed openly here, not discovered at tender.
04
Either a planning application to Cornwall Council or, where the work qualifies, a lawful development certificate confirming permitted development. Allow the statutory determination period plus time for validation, and expect the possibility of conditions attached to any approval.
05
The approved design becomes a full technical package with construction details, structural coordination and specification, submitted to Building Control as a full plans application. This is the set the builder prices and builds from.
06
Two or three builders price the same complete package, or you take a single contract route with one team responsible for both drawings and build. Comparing prices only means something when everyone is pricing identical information.
07
Work starts, Building Control inspects at stages, queries get answered as they arise, and at the end a completion certificate is issued. Keep it with the deeds, because it is the document a future buyer's solicitor will ask to see.
Frequently asked
Read next
What actually drives extension costs in Cornwall — ground conditions, access, glazing, exposure and finish level — and how to compare builder quotes fairly.
Approval is the middle of the process, not the end. Conditions, building regulations, structural design, tendering and the checks to complete before work starts on site.
A realistic Cornwall planning timeline — survey, design, validation, consultation, decision and discharge of conditions, with the stages that actually cause delay.
Book the free first consultation and we will walk the property and set out the route.
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