I have planning permission. What drawings do I need next in London?

The order of jobs after the planning letter

Most delays at this stage come from doing things in the wrong order: a builder booked before the steel is sized, or notices served after the start date. The sequence below is the one we run for an extension, and each step feeds the next.

Building control's own timetable is short if the drawings are complete. On a full plans application, GOV.UK says "You can expect a decision within 5 weeks, or 2 months with your consent" (GOV.UK, how to apply). Our post on what drawings building control needs for an extension covers what the officer reads on each sheet.

Structural calculations: the part that holds the drawings up

Knocking the back of the house out for a kitchen extension, opening a load-bearing wall or adding a loft floor means new loads, and building control will ask for calculations. The engineer names the beam, the padstones and the foundation; the drawings then show exactly those, so the two documents never disagree on site.

Our structural drawings and calculations start at £745. We order them in parallel with the building regulations drawings rather than after, which is the main reason a set reaches building control in one go instead of coming back with questions.

Party wall notices: start the clock early

The Party Wall etc. Act 1996 has its own deadlines, and they run from the date you serve notice, not the date planning was granted. For work to a shared wall, such as cutting in a steel, the notice must be served "at least two months before the date on which the proposed work will begin" (Party Wall etc. Act 1996, section 3).

Digging foundations near a neighbour is caught too: the Act applies to excavation "within a distance of three metres measured horizontally" of their building that goes deeper than its foundations, with notice "at least one month before beginning to excavate" (section 6). Our party wall notices start at £45 per adjoining owner, and we serve them as soon as the start date is known.

Conditions on the permission, and the three-year clock

Read the decision notice line by line. Many London permissions carry conditions requiring samples of materials, a construction plan or tree protection details have been approved. Work started before those are cleared can put the whole permission at risk. Once the details go in, the council must decide "within a period of 8 weeks" unless you agree a longer time in writing (Development Management Procedure Order 2015, article 27), so build that wait into your programme.

Dealing with conditions is a separate service from building regulations drawings; we prepare discharge of conditions packs too, priced on our pricing page. The other date to note is the end of the permission. Unless the notice says otherwise, development must begin within three years of the grant (Town and Country Planning Act 1990, section 91), and an approval left on a shelf past that date is gone.

Getting builder quotes you can compare

Builders cannot price an extension properly from planning drawings, because the cost sits in exactly what those drawings leave out: steel, foundation depth, insulation, drainage. Quotes from a planning set tend to be guesses padded for risk, and the difference turns up later as extras.

Send the same approved building regulations set to three builders and each prices the same job. Our post on what drawings builders need to price an extension explains which sheets they read. A building notice route can save the drawing stage on a small job, but GOV.UK notes that "You do not get formal approval like you do with full plans", so you have nothing approved to quote against.

When you are ready, send us your decision notice and the approved drawings through the building regulations drawings page, and we will quote the conversion at £745 or tell you if something on the planning set needs looking at first.