Short answer: a brick porch needs proper concrete footings dug to firm ground, with drains, manholes and damp-proofing dealt with before any walls go up.
Footings and clay soil
Much of West London sits on clay, which swells and shrinks with the seasons. Footings must be deep enough to reach stable ground, and nearby trees can mean going deeper.
Drains and manholes
If a manhole or drain sits where the porch will go, it may need to be moved or covered with an approved recessed cover. This is checked on the survey.
Damp-proofing
The porch floor and walls need a damp-proof course and membrane that tie in with the house so moisture does not track inside.
Why it matters
Groundworks are hidden once the porch is built, so cutting corners here causes cracks later. See how long a porch takes to build.
Next step
Homeowners in Isleworth, Feltham and Southall can try the Porch Planner or book a free estimate.
Local porch guides