The short answer: treat it as an extension before treating it as a kitchen
A wet-kitchen extension can affect the approved building footprint, gross floor area, external walls, structure, roof, drainage and neighbour-facing conditions. Cabinet layout matters, but it comes after the route for the added space is understood.
Start with the approved and existing plans, current rear-yard condition and the outcome the household needs. Ask whether the proposal is internal reorganisation, an addition within the applicable rules, or a larger alteration requiring a different professional and approval route.
Compare the proposed space with the approved house
URA states that enlarging or relocating rooms within a landed house may not require planning permission in the examples and conditions it describes. That should not be read as automatic permission to enclose or extend an external area.
For terrace-house A&A, URA's current criteria consider additional gross floor area, external-wall replacement, structural changes, roof works and the prevailing building envelope. The familiar 50% shorthand is only one part of that assessment. A Qualified Person should check the real proposal and property records where the work goes beyond an interior layout change.
Resolve the connection between new and existing structure
The rear wall, existing columns and beams, floor slab, foundations and the proposed opening all affect how the extension meets the house. A wide opening for an indoor-outdoor kitchen cannot be assumed to be a finishing decision.
Record which elements are retained, removed or newly supported. Structural feasibility and temporary-work needs should be established before the roof, glazing or cabinet set-out is treated as final.
Design the roof and weather junction as one system
An extension creates edges where new roof work meets an older wall, roof or upper-storey facade. Falls, flashings, gutters, downpipes, penetrations and maintenance access need coordinated details rather than separate trade assumptions.
Photograph existing stains, ponding, overflowing gutters and low points before work starts. New ceilings or cabinets should not conceal an unresolved water path.
Map rainwater, kitchen wastewater and floor levels early
Show existing drains, downpipes, sanitary points, inspection access, external ground levels and the intended sink or floor-trap positions. The project team can then identify which routes must be checked and which technical requirements may apply.
The finished floor, threshold and external falls should be reviewed together so routine washing or heavy rain does not create an avoidable backflow, ponding or step problem at the new junction.
Coordinate heat, ventilation, gas and electrical loads
Confirm the actual hob, hood, ovens, refrigerators, freezers, water heaters and other heavy-use appliances. Their power, ventilation, clearance and service-access needs affect the wall, ceiling and cabinet plan.
A wet kitchen that is partially enclosed also needs a deliberate path for heat, odour and make-up air. Equipment specifications and the applicable professional or authority requirements should govern the solution, not a generic kitchen drawing.
Plan access, neighbours and temporary household use
Rear extensions can involve excavation, structural work, roofing, wet trades and debris movement in a constrained area. Identify how workers and materials reach the rear, what must be protected, and whether the existing kitchen or services remain usable during each stage.
For the first review, send the approved and existing plans, rear and side photographs, known drainage or leak issues, the appliances to be used, desired enclosure, budget range and target timing. The useful outcome is a list of feasibility checks—not an instant promise that every square metre can be enclosed.
Check the current official guidance against the proposal.
These links support the planning points explained above. Requirements can change and the official pages should be checked again when the project scope is developed.
Use the note as a starting point.
Send the floor plan, site photos and rough scope for an initial project review.
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