Flat Conversion DrawingsFrom £1,195
How much do flat conversion drawings cost in London?
Drawings to convert a London house into two flats cost our fixed £1,195, which includes the measured survey visit, and the council adds £610 for the additional dwelling. Those are the planning-side costs; the larger bill is what building regulations ask of a house that becomes two homes, and this post sets out each piece.
The short answer: our fee, the council's fee, and what follows
For a conversion into two flats we charge £1,195. That covers the measured survey of the whole house, existing and proposed plans for every floor, elevations where they change, a site plan with the bin and cycle storage shown, and the application submitted as your agent.
The council's planning fee for a single house becoming two or more homes is £610 for each additional dwelling when fewer than 10 are created (fees schedule, category 12). A two-flat conversion creates one additional dwelling, so the fee is £610. At 10 to 50 dwellings the rate rises to £659 each, which will matter only on a large block.
- Our conversion drawings
- £995
- Our measured survey visit
- £200
- Total
- £1,195
Why planning permission is always needed
Under section 55 of the Town and Country Planning Act, the use as two or more separate dwellinghouses of any building previously used as a single dwellinghouse involves a material change in the use of the building. A material change of use is development, so it needs permission.
That removes the cheaper routes a loft or extension may use. There is no certificate of lawfulness for a flat conversion on a house with no flats, and no prior approval. The council decides it against its housing policy, which may ask whether family-sized homes in the area are being lost. We check your borough's policy on the survey day and tell you if a conversion is a long shot before you spend the council's fee.
What building regulations add to a conversion
A house that becomes two flats must meet the fire requirement that there are appropriate provisions for the early warning of fire, and appropriate means of escape in case of fire, and in practice that means a protected route from the upper flat to the street, fire doors, and alarms linked through both homes. Sound insulation between the flats is the other big item, usually floor and wall upgrades the drawings must show.
Our building regulations drawings start at £745 for a project of this kind, and the post on what they cost explains building control's separate charge. Both are in addition to the planning set above, and a conversion needs them whether or not it also extends.
Room sizes you cannot draw around
The government's nationally described space standard sets minimum floor areas for new homes, and a council can apply it to conversions through its local plan. Its smallest figure is for a one-bedroom home for one person, where the floor area is 39 square metres, or 37 with a shower room instead of a bath.
A typical Victorian house on two floors splits more easily into a ground-floor flat with garden access and a first and second floor maisonette than into one flat per floor. We test both layouts against the floor areas, the stair position and the fire route on the survey drawings, and draw the one that works rather than the one that adds most bedrooms.
When the work also needs an extension
Many conversions add a rear extension or a loft to make the upper flat habitable. If you want that in the same application, our fixed fee for a conversion with an extension is £2,095, which draws both together, so the council sees one scheme and one fee structure rather than two.
If you only need to split the house internally, the lower price applies. Our guide to permission for converting a house into flats covers the policy tests in more depth, and our flat conversion drawings page shows the full service.
What you do not need to pay for twice
The survey is the item most people pay for twice, once to a separate surveyor and once again when a drawing firm re-measures. Ours is inside the fixed fee, and the measured plans are the same ones the building regulations set is later drawn from.
The ownership certificate is also not optional. An application is invalid without the relevant ownership certificate completed, and a conversion of a leasehold house or a house with a shared freehold needs the right one. We ask for the title details at the start and complete it for you.
Sources
Every figure in this article, where it comes from and a link to the original.
- £610: Statutory fee from 1 April 2026, fees schedule category 12(1)(a): change of use from a single dwellinghouse to fewer than 10 dwellinghouses, per additional dwellinghouse. assets.publishing.service.gov.uk
- £659: Statutory fee from 1 April 2026, fees schedule category 12(1)(b): change of use from a single dwellinghouse to 10 to 50 dwellinghouses, per additional dwellinghouse. assets.publishing.service.gov.uk
- involves a material change in the use: TCPA 1990 s55(3)(a): (source wording: "the use as two or more separate dwellinghouses of any building previously used as a single dwellinghouse involves a material change in the use of the building"). www.legislation.gov.uk
- appropriate means of escape in case of fire: Building Regulations 2010 Sch 1 Part B1: (source wording: "appropriate provisions for the early warning of fire, and appropriate means of escape in case of fire"). www.legislation.gov.uk
- 39 square metres: Nationally described space standard: 1 bedroom, 1 person dwelling minimum gross internal floor area (source wording: "the floor area may be reduced from 39m2 to 37m2"). www.gov.uk
- ownership certificate completed: PPG Making an application: (source wording: "An application is not valid, and therefore cannot be determined by the local planning authority" unless the relevant ownership certificate has been completed). www.gov.uk
Questions people ask
Is the £610 council fee included in your price?
Do I pay VAT on your fee?
Can I convert a house into flats without planning permission?
Will the council say yes?
Do you do the fire and sound details?
Photographs: Brett Wharton (Unsplash License); Tima Miroshnichenko (Pexels License).
Flat Conversion Drawings: a fixed fee from £1,195
Read more on the flat conversion drawings service page, or send your address below and we reply within one working day.
Flat Conversion Drawings
from £1,195
£995 drawings + £200 survey (£1,195 total)
Every price is the full fixed fee you pay. No VAT is charged. Council application fees are paid to the council separately.
What you get
- Measured survey of the whole house, included in the fixed fee
- Existing and proposed plans for every floor
- Elevations and a site plan with bin and cycle storage
- A check of your council's housing policy on conversions
- Application forms, ownership certificate and submission