Flat conversion drawings in London

Why a house-to-flats conversion needs planning permission

There is no permitted development shortcut. The Town and Country Planning Act 1990 treats it this way: Use of a single dwellinghouse as two or more dwellings is a material change of use. An application is therefore the route, and our planning drawings set is the foundation for it.

The council fee is £610 for each dwelling created, from the current fee table, and is paid to the council. A two-flat scheme therefore carries it twice.

Space standards for each flat

Every new flat is measured against the nationally described space standard. For floor area it sets out: Minimum GIA: 1b1p 39 m² (37 m² with shower), 1b2p 50 m², 2b3p 61 m², 2b4p 70 m² (one-storey dwellings); 3b4p 74 m², 3b5p 86 m². Rooms have their own minimums: Single bedroom at least 7.5 m² and 2.15 m wide; double at least 11.5 m², one double at least 2.75 m wide (others 2.55 m).

Height counts as well. The national test is: Floor to ceiling at least 2.3 m for 75% of GIA; areas under 1.5 m headroom not counted. Inside London the bar is higher. The London Plan asks for a floor-to-ceiling height of 2.5 m, which can rule out some basements and attic floors.

Outdoor space is the third check. The London Plan sets a rule for outdoor space: Min 5 m² private outdoor space for 1-2 person dwellings plus 1 m² per extra occupant, min 1.5 m deep and wide. A small terraced garden may need to be divided with care.

Sound, fire and cost beyond the drawings

Neighbours in a converted house hear each other, so Approved Document E sets the sound targets for conversions: Separating walls 43 dB DnT,w+Ctr (min); floors and stairs 43 dB airborne (min), 64 dB L'nT,w impact (max) for dwellings formed by material change of use. We draw the floor and wall build-ups that meet them.

Cost can also rise through the Community Infrastructure Levy. The relevant rule reads: The under-100 m² CIL exemption does not apply where a new dwelling is created. We flag any liability in the next-steps pack we hand over at the end.

Once planning is in hand, the building regulations drawings turn the scheme into technical sheets coordinated with the structural engineer.

What flat conversion drawings cost

Our published fee for a two-flat scheme starts at £1,195, VAT included. Larger schemes with more flats are quoted from the same price list after the free constraints check, never from a guess.

If the council asks for changes, we redraw at no charge until approval. That commits our fees, not the council's decision, and we never promise a result.

If you plan to let rooms rather than create flats, see our HMO conversion drawings. If the building is leasehold and the freeholder must consent to the works, the licence to alter drawings page explains that side.

How the work is run

You send the address and the number of flats you want. The constraints check covers conservation areas, listed status, Article 4, trees, flood zone and planning history, then we send the fixed quote.

A measured survey follows. We try layouts in 3D, you pick one in writing, and the design is frozen. A second chartered technologist checks every sheet, never the drawer, and a senior review signs it off.

Drawings are normally ready about a week after the survey. We submit through the Planning Portal and answer the case officer, with amendments inside five working days.

Layout choices that make or break the scheme

Stacking comes first. Bedrooms over living rooms, or a bathroom above someone else's bedroom, make sound and drainage harder. We test layouts so wet rooms and noisy rooms line up from floor to floor wherever the house allows.

Entrances are next. Two flats need separate, safe front doors, bin and cycle storage and a protected escape route from the upper flat. Squeezing these in late is how schemes lose space, so we place them first.

The garden is the third choice. Sharing it, dividing it or giving it to the ground-floor flat each changes the outdoor space test. We draw the option you prefer and say plainly if it misses the standard. Once the flats exist, each will need lease plans if you plan to sell or let them.

Flat conversion drawings by council

Boroughs read the London Plan through their own housing policies, so one layout can pass in one borough and not in the next. Council pages give the local figures: conservation areas, Article 4 directions and listed buildings.

See architectural drawings in Camden for an example, or choose any council from architectural drawings by area.