Change of use drawings in London

Houses and small HMOs: Class C3 against Class C4

The two classes are defined narrowly. Class C3 means: Dwellinghouse use by a single household, or up to six residents living together as a single household. Class C4 means: Small HMO: a dwellinghouse used by not more than six residents as an HMO (Housing Act 2004 s254).

Moving between them follows a simple rule with a catch: C3 to C4 (and back) is permitted development unless removed by an Article 4 direction. Because councils can make that direction for part or all of their area, the address decides your route, not the general law. Architectural drawings in Camden shows how a council page sets out its local position.

Anything bigger than a small HMO, and any conversion into self-contained flats, sits outside that permitted route and needs an application. Our HMO conversion drawings and flat conversion drawings pages deal with those schemes.

Shops and offices to homes under Class MA

Class MA is the route for turning commercial premises into homes without a full application. The rule is Class E to C3 by prior approval after 2 years' continuous Class E use. The council has 56 days to decide, and no date is ever promised to you.

Prior approval is narrow. The council can look only at the matters the Order lists, such as flood risk, transport and the effect on neighbouring uses, and it cannot reopen whether homes are acceptable in principle. Our prior approval drawings page walks through what a complete submission needs.

Check the building's history early. A shop that has stood empty or a unit split between uses can fail the continuous-use test even when it looks like a shop from the pavement.

Space and sound: the limits that shape the layout

Two standards limit what a building can become. For space: Homes created under PD must meet the nationally described space standard. That sets minimum floor areas by bedroom count, so the number of flats a building can hold is a design question long before it is a planning one.

For sound, Approved Document E sets the targets for homes formed by a change of use: 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. Older buildings frequently need extra layers in party floors, which costs ceiling height.

We test every unit against both standards on the survey, before layouts are shown, so you do not choose an option that fails later.

What a change of use set includes

The contents follow the route. A full application needs location and block plans, existing and proposed layouts, elevations and sections, and the floor area of each unit marked against the space standard. Prior approval needs the particular details the Order lists.

Areas and dimensions are modelled once in Revit, so every sheet quotes the same figures. A second chartered technologist checks each unit against the space standard, and the set normally follows the survey within about a week. If the scheme also changes how a lease is drawn, our lease plans service supplies those plans.

What the council charges

To change a building to separate dwellinghouses the fee is £610 for each dwelling in a scheme of not more than ten. Other changes of use of a building or land carry a fee of £610. The council collects these sums itself, on top of our price.

The right figure depends on the route and the number of homes, so we confirm it from the fee table before you commit.

Why change of use applications fail

The commonest failure is lawful use. If the current class cannot be shown, the officer cannot say what is changing. We gather planning history and, where needed, evidence of established use before any drawing starts. Where use is uncertain, a lawful development certificate can settle it first.

Other avoidable problems include rooms under the space standard, no bin or cycle storage and poor outlook from ground-floor flats. We design these out from the first sketch, not at the validation stage.