If you own one of Ealing's many Victorian or Edwardian terraces, a basement conversion can be one of the few ways to add real living space without touching the footprint of your garden. Costs vary enormously depending on whether you're tanking an existing cellar or digging down to create a new one, so here's a realistic breakdown based on what we see across Ealing, Hanwell and West Acton.
The single biggest factor is whether you already have a cellar to convert or need to dig one from scratch. Many older Ealing houses, particularly around West Ealing and the Grange area, have a shallow Victorian cellar with low headroom. Underpinning the walls to lower the floor and gain standing height is structural work, and it's where most of the budget goes.
Waterproofing method matters too. Ealing sits on London Clay with pockets of made ground near the Brent and the Grand Union Canal corridor, so a proper tanking or cavity drain membrane system with a sump pump isn't optional, it's standard practice on almost every job we quote here.
These are broad ranges, not quotes, because every house and every soil survey throws up different numbers:
Basement works almost always need planning permission in Ealing, even where other extensions might be permitted development, because excavation and light wells fall outside the usual allowances. If your road sits within one of Ealing's conservation areas, such as Ealing Common, Hanger Hill Garden Estate or parts of Gunnersbury, expect extra scrutiny on light wells, railings and any change to the front garden.
Because most Ealing basements run under a terrace or semi, you'll need a party wall agreement with your neighbours before digging starts, and a structural engineer's method statement is usually required by the council and by the party wall surveyors alike. Build this into your timeline early, it regularly adds six to ten weeks before a spade goes in the ground.
A trial pit or borehole survey is worth commissioning before you fix a budget, not after. Properties nearer the Brent and the canal can have higher water tables and softer made ground, which pushes up the specification of the drainage system and sometimes requires a sump and pump as standard rather than a passive drain. Houses further from the river, around Hanger Hill and West Acton, tend to sit on firmer clay, which is generally more predictable to underpin but still requires careful temporary shoring given the age and condition of Victorian brick foundations.
Get a structural engineer and a waterproofing specialist involved before you finalise the design, not after, since redesigning a drainage strategy midway through underpinning is one of the most common causes of cost overruns we see. Ask any contractor quoting the job how they price variations if the trial pit findings differ from the final dig, and get that in writing rather than verbally agreed on site.
Almost always yes, because excavation work and light wells sit outside permitted development rights, and conservation areas such as Ealing Common add further restrictions on light wells and front garden changes.
A full underpinned conversion typically takes four to seven months on site once planning and party wall agreements are in place, with the structural underpinning and waterproofing stages taking the longest.
Yes, most Ealing terraces and semis share a party wall, so you'll need a party wall agreement and a structural method statement before excavation starts, and some vibration and noise during underpinning is unavoidable.
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