The Mirion blog
Common Extension Problems in London — and How to Avoid Them
Extensions in London come with specific challenges — from Victorian foundations to party walls to drainage. Here are the most common problems and how we prevent them.
AI-generated illustration; not a completed Mirion project. A small brick rear addition with a low dark roof, gutter, downpipe and glazed door.
Extensions in London are not like extensions elsewhere
London properties — especially Victorian and Edwardian terraces — come with specific challenges. Here are the problems we see most often and how we prevent them.
Unexpected ground conditions
The problem: London clay soil expands and contracts. Old properties often have shallow foundations.
How we prevent it: We carry out a ground survey before quoting.
Drainage issues
The problem: Many older London properties have shared drainage near the extension footprint.
How we prevent it: We check drainage plans early and include any required approvals in the timeline.
Party wall disputes
The problem: Extensions near shared walls need a party wall agreement.
How we prevent it: We advise on party wall requirements during the survey.
Poor communication during the build
The problem: Many extension problems are communication problems.
How we prevent it: We give you a single point of contact throughout the project.
The best extension is a well-planned one
Most extension problems are preventable with proper surveying, honest communication and realistic planning.