Double-storey extension drawings in London

Conservation areas and upper floors

The position in protected areas is blunt: No rear extension of more than one storey under PD on article 2(3) land. A conservation area house with a long garden is therefore usually a planning case from the start.

That is not a refusal. It means the design is judged on merit, and the usual concerns are bulk, the view from neighbouring gardens and the character of the street. A set-back first floor, a lower ridge or a hipped roof can all help, and we draw those options for you to compare.

Single-storey options can be quicker to deliver, so we always show the simpler choice beside the two-storey one. See rear extension drawings for that comparison.

Windows and roof design on the upper floor

Two rules decide the look of the upper storey under permitted development. First, windows in a side wall: Upper-floor side windows obscure-glazed and non-opening below 1.7 m above floor. Second, the roof: Roof pitch of a 2+ storey enlargement to match the original house so far as practicable.

The first protects the neighbour's privacy, which is why upper-floor side windows in London terraces are often small and high. The second keeps the extension from looking like a different building stuck onto the original, and it is the reason matching a hipped or pitched roof takes more care than it sounds.

Even where planning rules are looser, officers use the same ideas as a guide. We design to them so the application reads as sensible.

Fire safety and the escape window

A first-floor bedroom brings a fire rule that a single-storey room does not. The Approved Document sets the standard for the way out: 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.

That affects the window you choose and its position, so it belongs on the drawings, not left for site. A fashionable fixed pane over the bed will not do in a room that needs an escape route.

Our building regulations drawings carry the fire details, stair and structure through to the building control submission.

Structure, energy and party walls

A second storey on an existing house puts a new load on the ground floor walls and foundations, often through steel at the opening. Our structural calculations coordinate the engineer's design with the drawings.

Energy limits for the new walls, roof and floor 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.

Party wall rules usually apply, since the new storey sits against the neighbour's house. A cut into a shared wall needs: Party structure notice at least 2 months before work. Foundations close to the neighbour fall under: Adjacent excavation notice at least 1 month before work: within 3 m and deeper than the neighbour's foundations, or within 6 m and cutting a 45° line from their foundations. We prepare the notices through party wall notices.

Cost and what you receive

Double-storey extension drawings start at £1,295, VAT included, fixed and published before you commit. The council's householder fee is £548, paid to the council and separate from ours.

You receive plans for both floors, elevations, sections and the usual location and block plans, plus submission if you want it. Every sheet is checked by a second MCIAT chartered technologist before it goes in.

We redraw at no charge if the council asks for changes, until approval. That is a promise on our fees and not on the council's decision.

Two-storey extension drawings by council

Councils vary a good deal on how much two-storey bulk they will accept next to a neighbour. Look up your borough under architectural drawings by area for the local conservation area and Article 4 figures.

Considering the roof instead? A loft conversion adds floor space without extending the footprint, and the full set of extension shapes is under house extension drawings.