Double-storey extension drawings in Merton

Reading Merton's streets

Merton has 28 conservation areas and Historic England lists 243 entries in the borough. Domestic gardens covered 27.2 per cent of its land in the government's land-use survey, which is a good deal of rear space for rear additions, but also a good deal of neighbouring windows to protect.

Inside a conservation area: No rear extension of more than one storey under PD on article 2(3) land. Our architectural drawings in Merton page covers the borough-wide constraints.

Upper-floor design under permitted development

Where permitted development applies, two conditions shape the first floor. Upper side windows: Upper-floor side windows obscure-glazed and non-opening below 1.7 m above floor. Roof: Roof pitch of a 2+ storey enlargement to match the original house so far as practicable.

A lawful development certificate in Merton can confirm that a design meets them. Where it does not, we move to a householder application, drawn as in our planning drawings in Merton.

Fire escape, energy and party walls

A first-floor bedroom needs an escape window: Escape window: unobstructed openable area at least 0.33 m², at least 450 mm high and 450 mm wide, bottom of opening no more than 1100 mm above floor. New elements must meet these limiting values: 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. For shared walls: Party structure notice at least 2 months before work.

How quickly Merton decides householder applications

Merton decided 759 householder applications in its latest published year, and granted 92.9 per cent. Only 85.2 per cent were decided within the statutory period or an agreed extension, so we plan a timetable with some margin.

The figures cover every householder scheme and say nothing about any one house.

Showing officers what the extension does

Because Merton gives no depth figure for us to quote, the drawings carry the argument. We draw a plan of both floors with the neighbours' windows marked, a section through the extension and the boundary, and rear and side elevations that include the house next door. Where it helps, we add a daylight view that shows the room behind the nearest window.

An officer's obvious questions are best answered on the sheet itself: is the first floor set in from the boundary, does the roof match the original, and does the new window look into a garden or a room?

We also advise on materials and brickwork at this stage. A first-floor addition in a matching brick with a roof pitch that follows the original reads as part of the house, while a mismatched finish reads as an add-on. Both are cheap to draw correctly and expensive to change after approval.

Your drawing set, price and neighbours

A Merton set shows both floors, the roof section, elevations and plot plans. It starts at £1,295 with VAT included, fixed before you commit, and we redraw free until approval if the council asks for changes.

For a smaller scheme, see rear extension drawings in Merton. The same service is available in Sutton, Wandsworth and Kingston upon Thames, each with its own guidance.