Side return extension drawings in London

The permitted development limits for side extensions

Without a planning application, a side extension has to be small. The national rule is: Side extension: single storey, max 4 m high, max half the width of the original house. Near the boundary the eaves are capped as well: Eaves no higher than 3 m where within 2 m of the curtilage boundary.

Materials count too: Exterior materials must be of similar appearance to the existing house (conservatories excepted). A bold contrast in brick is a planning matter, not a permitted development one.

Check the plot too. Your house may already have been extended, and earlier work counts towards the limits, so the survey measures the original footprint before we say what is possible.

Conservation areas change the route

This is the catch that surprises owners. The rule reads: No side extensions under PD on article 2(3) land (conservation areas etc.). In a London street of Victorian terraces, that means many side returns need a householder application, however modest.

A planning application is not a bad outcome. It lets the officer see the roof, the glazing and the materials in context, and a well-drawn scheme in a conservation area is treated on its merits.

We run the address check first. If the house is in a conservation area, we plan the application from the start through planning drawings, and the council's fee for a householder extension is £548, paid separately to the council.

Glazing, heat and the Building Regulations

A side return usually has a lot of glass, which is what makes it good and what makes the energy rules awkward. For new elements in existing homes, the limits are: New elements in existing dwellings, limiting U-values W/(m²·K): roof 0.15, wall 0.18, floor 0.18, windows 1.4 (or WER Band B), doors 1.4.

Glazing is capped on the simple route: Windows, roof windows, rooflights and doors in an extension should not exceed 25% of the extension floor area plus the area of openings removed or covered. A glazed roof and a full-width door set can exceed that cap, in which case the design needs a calculation or a trade-off, which we cover under SAP calculations.

Taking down the old flank wall means a beam. We coordinate the engineer's sizes through structural calculations so the openings on our drawings match.

Party walls on a side return

Because the extension sits against the neighbour's wall, notices are almost always needed. Building a new wall up to the line is covered by: Line-of-junction (new wall) notice at least 1 month before work. Cutting into a shared wall is covered by: Party structure notice at least 2 months before work.

Serve the notice early, with clear drawings. A neighbour who understands the plan is far more likely to agree, and the programme is protected. Our party wall notices service prepares them to match the design.

Gutters and flashings along the boundary are a common dispute, so the junction section is one of the sheets we draw in most detail.

Cost and what you receive

Side return extension drawings start at £745, VAT included, fixed and published before you commit. The price list covers the other shapes too, so you can see what adding the rear changes.

You receive existing and proposed plans, elevations, sections, location and block plans, with forms and Planning Portal submission if you want them. A second MCIAT chartered technologist checks every sheet before it leaves us, and we redraw at no charge until approval.

Going further than the side alone? A wraparound extension combines the side return with the rear.

Side return drawings by council

Conservation areas are decided borough by borough, so the page for your council matters. Find yours under architectural drawings by area, where the local counts of conservation areas and Article 4 directions are set out.

To compare every shape before choosing, see house extension drawings.