Commercial to Residential Conversion Calculator

Class MA (formerly Class O) permitted development rights allow the conversion of commercial buildings (Use Class E — shops, offices, restaurants) to residential use (Class C3) without full planning permission. You need 'prior approval' from the council, which costs £100 per unit. The building must have been in commercial use for at least 2 years.

Typical conversion costs are £25,000-£50,000 per unit depending on the condition of the building and the specification required. Add professional fees (8-12% of build cost), prior approval (£100/unit), building control, and finance costs. Total project costs typically equal 40-60% of the gross development value.

Prior approval is a simplified planning process for permitted development. The council can only assess specific matters: flooding, contamination, highways, noise, natural light, and the impact on the commercial viability of the area. They cannot consider design, density, or the principle of development. Decisions must be made within 56 days.

Yes, since April 2021, all residential units created through permitted development must meet the Nationally Described Space Standards: a minimum of 37m² for a 1-bed/1-person unit and 50m² for a 1-bed/2-person unit. Adequate natural light must also be provided to each habitable room.

Generally no. Permitted development conversions are typically exempt from the Community Infrastructure Levy (CIL) because no new floorspace is created. However, any new-build extensions as part of the scheme may attract CIL. Check with your local planning authority as rules vary by area.