House extension drawings in Hounslow

Going up: two-storey extensions in Hounslow

Two-storey side extensions are asked to show 1 m set-back; less than half width; 0.5 m set-down. The set-back and set-down are what stop a side extension turning a pair of semis into a terrace.

Two-storey rear extensions are harder. The guidance calls them rarely acceptable on mid-terrace houses, and elsewhere asks for half width; 2.5 m deep; 2 m separation. An extra storey above an original two-storey outrigger will generally be refused.

Wraparound extensions that join a side and a rear extension on a corner plot will be refused outright, which is worth knowing before anyone sketches one.

Heritage, Green Belt and the borough's constraints

Hounslow has 33 conservation areas, 3 Article 4 directions and 519 listed building entries, and about 22 per cent of the borough is Green Belt. It also contains 1 World Heritage Site, which brings its own protected setting.

Inside a conservation area, side extensions lose their permitted development rights, and a listed house needs its own consent. Our free constraints check reads the address against each of these layers before we quote.

The borough's Character, Sustainability and Design Codes SPD sits alongside the extension guidelines and is read with them for materials, roof forms and boundary treatments.

Prior approval for larger rear extensions in Hounslow

Where permitted development applies, a single-storey rear extension may follow the national rule: 3 m (attached) / 4 m (detached) beyond the original rear wall, single storey. Beyond that, the larger home extension route asks the council to look only at the effect on neighbours, and it has 42 days to respond.

Hounslow's record on that route is worth a look before choosing it. In its latest published year the council granted 20 larger home extension prior approvals and refused 59. Refusals outnumber grants, so it is worth weighing the neighbour consultation against a full householder application.

A Lawful Development Certificate in Hounslow is the written proof that an extension is permitted development, whichever route you take.

How Hounslow decides householder applications

The council decided 689 householder applications in its latest published year. It granted 78.5 per cent and decided 97.8 per cent within eight weeks or an agreed extension. The fee for an extension to a single dwelling is £548, paid to the council.

Those figures describe every householder project in the borough, not yours. We use them to plan the timetable, not to forecast a decision.

What you receive and the price

Our Hounslow extension sets show existing and proposed floor plans, elevations and sections, with the location and block plans, drawn from one model. Drawings start at £695 with VAT included, are checked by a second MCIAT chartered technologist, and are normally ready about a week after the survey.

If the council asks for changes we redraw at no charge until approval. For the whole borough see architectural drawings in Hounslow, or compare the rules across the river in Richmond upon Thames.