Drawings to convert a house into two flats, £1,029 in total
Turning one house into two homes is a change of use in law, so it needs a planning application first, then building regulations. We measure the house, draw both flats to the space standard and submit: £879 plus the £150 survey.
- £879 drawings + £150 survey (£1,029 total)
- Both flats drawn to space standards
- Free redraws until approval
What do drawings for a two-flat conversion cost?
The drawings are £879 and the measured survey £150, which is £1,029 in total with no VAT to add. That buys the planning set for both flats: layouts, elevations, access, bins and cycles. Building regulations drawings for the same house are a separate set, priced at the drawings fee alone because the survey is charged once.
What the £1,029 covers
- A measured survey of every floor, the stairs, the cellar if there is one and the garden
- Existing and proposed plans for both flats, with each flat’s floor area marked against the space standard
- Front, rear and side elevations, with any new doors, windows and bin store drawn in
- A site plan showing the separate entrances, cycle storage and refuse arrangements
- The application form, certificates and a short statement setting out how the two homes meet the standard
- Checking by a second chartered technologist, submission and replies to the officer, with free redraws until approval
Why two flats always need planning permission
Because the Act says so. Section 55 lists the use of a building as two or more separate dwellinghouses, where it was one before, as a material change of use (section 55(3)(a)). There is no permitted development shortcut that does it for you. The question is never whether to apply, only whether your borough will say yes.
That is a policy matter. Many London boroughs resist the loss of family-sized houses, set a minimum floor area for any flat, and expect a proper separate entrance. We read the borough’s rules before we quote, so you hear early if a house is a poor candidate.
Laying out two flats in a house built for one
Start with the stairs. The common route to the upstairs flat takes space from the ground floor, and what is left for the ground floor flat decides whether it clears 50 m² for one bedroom (space standard). We test that arithmetic on the survey before any design work, so there are no surprises on the drawing.
Then the practical details councils ask about: a front door each, bins that do not block the pavement, a safe place for bicycles, and a garden arrangement that gives the ground floor flat a private space.
- Floor area of each flat against the standard
- Separate front doors and a clear shared hall, if any
- Where the bins and the bicycles go
- Which flat gets the garden, and how it is fenced
What happens after planning
Building control comes next, and it is stricter than many owners expect. Making a second home inside a house is a material change of use under the Regulations, and the sound insulation rules in Part E apply to the new floor and wall between the flats (Approved Document E). Fire protection between the homes and the escape route also matter (Approved Document B).
Our building regulations drawings set out that construction, and a fire strategy plan can be added where the layout is complex. A structural engineer will usually be needed for openings and new floors, which we coordinate.
What the law and the standards say about two flats
- Material change
- Using a building previously used as a single dwellinghouse as two or more separate dwellinghouses is a material change of use, so it is development needing planning permission. Town and Country Planning Act 1990, s.55(3)(a)
- 50 m²
- The national space standard sets a minimum gross internal area of 50 m² for a one-bedroom flat for two people on a single storey. Technical housing standards: nationally described space standard, Table 1
- 70 m²
- For a two-bedroom flat for four people on one storey the same table sets 70 m². Technical housing standards: nationally described space standard, Table 1
- 2.3 m
- The standard also asks for a floor-to-ceiling height of 2.3 m over at least 75% of the flat’s floor area, which is why we measure the heights in your loft and cellar. Technical housing standards: nationally described space standard
- Regulation 5(b)
- A building that contains a flat where it previously did not has had a material change of use, which brings the sound insulation requirements E1 to E3 into play. Approved Document E, Resistance to sound
- £610
- The national fee schedule lists £610 per dwellinghouse for a change of use to separate dwellinghouses where fewer than ten are made, from 1 April 2026. National fee schedule from 1 April 2026, published by Bradford Council
- 5 weeks
- A full-plans building regulations application is decided within 5 weeks, or 2 months by agreement. gov.uk, Building regulations approval: how to apply
Questions about converting a house into two flats
Can I turn my house into two flats without planning permission?
No. Using a house as two or more separate dwellings is a material change of use under section 55(3)(a), so you need an application.
How big does each flat have to be?
Councils usually apply the national space standard, which gives 50 m² for a one-bedroom flat for two people and 70 m² for a two-bedroom flat for four on one storey. Your borough’s own figures may be higher.
Will I have to soundproof between the flats?
Yes. A new flat is a material change of use, and Approved Document E sets standards for the floor and walls between homes.
Source: Approved Document E
Does the £1,029 include the council fee?
No. The council fee is paid to the council. The national schedule lists £610 per dwellinghouse for a change of use to separate dwellings, and your council confirms the figure.
What if I want three flats?
Then it is a different brief and a different fee, and we quote it after we have seen the house. Two flats is the case this price covers.
Other services people book with this one
Is your house a candidate for two flats?
Send the address and tell us how many floors there are. We check the borough’s flat policy and reply with a fixed fee.