Construction drawings in Barnet

Mixed housing, mixed constraints

Only 52.5 per cent of Barnet households live in a house, so a good share of local work is flats and conversions, where fire separation and sound matter as much as the extension itself. Owner-occupiers make up 52.7 per cent of households, so many clients are extending the home they live in.

The heritage layer is dense. The council publishes 16 conservation areas and 15 Article 4 directions covering 48 separate areas, and Historic England lists 651 entries inside the boundary. An Article 4 direction withdraws some permitted development, usually for windows, roofs and frontages, so the specification has to name the exact window pattern and roof covering the direction allows.

Green Belt covers 28 per cent of the borough. On a Green Belt plot the extension's volume was settled at planning stage; our job is to build exactly that volume and not a centimetre more.

Stairs, windows and alarms: where lofts and rear extensions get checked

Three details cause most rework. The first is the stair. The rules are: Private stair: rise 150-220 mm, going 220-300 mm, max pitch 42°, 2R+G 550-700 mm. For headroom, 2.0 m clear headroom over stairs. In a Barnet loft conversion the stair often lands under a sloping roof, so we draw the section through it before the design is frozen.

The second is the 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. The third is detection: All dwellings: fire detection and alarm system minimum Grade D2 Category LD3 (BS 5839-6), mains-operated smoke alarms to BS EN 14604.

None of this is optional extra detail. Building control reads these dimensions off the drawing, and a missing one becomes a query that stops the file.

How Barnet's decisions shape your programme

In the latest published year the council granted 80.2 per cent of householder applications and decided 95.1 per cent on time. Larger home extension prior approvals went differently: 18 granted and 103 refused. Many owners therefore end up on the full planning route, and the construction set waits for that decision.

The Planning Inspectorate decided 413 householder appeals here and allowed 50.6 per cent. These are past figures for the borough, not a forecast for your house. We use them only to plan when your build can realistically start.

What your Barnet set contains

A typical set holds foundation and floor plans, roof plan, sections, window and door schedules, a drainage layout and a written specification. New elements in an existing house 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.

The same drawings can serve building control, so ask about building regulations drawings in Barnet and, if the extension is the whole job, house extension drawings in Barnet. The full list for the borough is under architectural drawings in Barnet. Across the border, the same service is available in Enfield, Brent and Camden.