Cellar conversion cost: what it really costs in 2026
A Qome Snap Guide: quick, honest and no guff. Approximate figures, adjusted to your region inside Qome.
Snap answer
£1,500 – £3,750 /m²
Waterproofing an existing cellar starts around £1,500/m². Making it habitable runs about £2,700/m², and full living space with natural light around £3,750/m².
Takes4–10 weeksDisruptionModerate, work is below but the staircase area suffers
Cost at a glance
Option
Best for
Guide range
Waterproofed
Dry, usable storage
£1,500 /m²
Habitable
Insulated, heated, finished
£2,700 /m²
Full living space
Light wells, full spec
£3,750 /m²
Approximate guide figures, not quotes, Qome adjusts every price to your region.
What actually happens
Survey, head height, damp and structure assessed
Tanking or cavity-drain waterproofing installed
Floor lowered if head height demands it (the big cost)
Insulation, first-fix electrics and heating
Staircase improved; light wells cut if planned
Plastering, flooring and decoration
Price by region
Starting figures by region, the same honest baseline, adjusted for where you live.
London (Inner)from £2,300 /m²
London (Outer)from £2,000 /m²
South Eastfrom £1,800 /m²
East of Englandfrom £1,650 /m²
South Westfrom £1,600 /m²
Scotland (Highlands)from £1,400 /m²
West Midlandsfrom £1,400 /m²
North Westfrom £1,400 /m²
East Midlandsfrom £1,400 /m²
Scotland (Central)from £1,350 /m²
Yorkshirefrom £1,350 /m²
Walesfrom £1,300 /m²
North Eastfrom £1,300 /m²
Northern Irelandfrom £1,250 /m²
Popular choices
Cavity drain membranes (over tanking)Light wells and pavement lightsUtility-and-snug combinations
Rules & regulations
Building regulations always apply, waterproofing, ventilation, escape routes and head height
Lowering the floor usually means underpinning: structural engineer territory and Party Wall notices for terraces
Planning permission only if you alter the outside (light wells at the front)
Snap tips
Head height decides everything, under 2.2m and the floor must drop, which can double the budget
Get a waterproofing guarantee backed by insurance, not just the installer's word
Price it properly on Qome
Choose your options and see an honest, region-adjusted estimate, free.