Building regulation drawings cost in London for 2026

What are you actually paying for?

‘Building regs drawings’ is used loosely to mean everything between planning permission and a builder starting. In fact it covers three separate purchases from three separate parties, and quotes that look wildly different usually differ in how many of the three they include.

• The drawing package — produced by us. General arrangement plans, construction sections, structural layouts, specification notes and the schedule of compliance against each Approved Document. This is the £840 to £1,750 part.
• The building control charge — paid to the borough or to a registered building control approver. Covers plan checking and the site inspections through to the completion certificate. Roughly £600 to £1,400 on domestic work in London.
• Structural engineer’s calculations — a separate discipline. Beam and foundation design with calculations the approver checks. Commonly £450 to £1,200 on a domestic project.

How much do the drawings themselves cost?

The Complete package at £1,750 is the one most extension and loft clients take, because it produces the planning set and the building regulations set from a single measured survey and a single model. Buying the two stages from different practices means paying twice for the same existing-condition information, and it puts the burden of reconciling two drawing registers on you when the builder finds a discrepancy.

Where planning permission already exists and only the construction set is needed, we price from the approved drawings and the survey they were based on. Where the approved drawings came from someone else and no survey is available, a fresh measured survey is required first, because building control detail cannot be drawn against dimensions nobody has verified.

What does building control charge in London?

You have a genuine choice of control body, and it affects both cost and programme. Every London borough runs its own building control service, and private registered building control approvers compete with them.

Full Plans is worth the premium over a Building Notice on anything structural. Full Plans means the detail is checked and approved on paper before the builder is on site, so a fire-strategy or insulation problem costs a drawing revision rather than a rebuilt stair enclosure. A Building Notice defers every one of those decisions to a site inspector standing in front of finished work.

Regularisation is the expensive route nobody plans for: applying retrospectively for work already built without approval. Beyond the higher charge, the inspector will normally require opening up completed finishes to verify what is behind them, and there is no completion certificate until they are satisfied.

What makes building regulation drawings more expensive?

• Number of structural interventions — each removed wall, new opening or replaced purlin is a beam to design, detail and check. A loft with two steels is a different job from one with six.
• Foundation conditions — London clay with mature trees nearby regularly drives foundations to 2.5 metres or deeper, or to a piled and beamed solution with its own drawing set.
• Drainage — building over or within 3 metres of a public sewer means a build-over agreement with Thames Water, a drainage strategy drawing, and a lead time that often exceeds the planning decision.
• Fire strategy complexity — a two-storey house becoming three storeys, an inner room created by an extension, or a flat conversion each change the escape strategy for the whole building.
• Party wall interfaces — work bearing on a shared wall needs detailing that satisfies both the approver and the party wall surveyor’s award.
• Conservation area or listed status — Part L compliance has to be achieved without the standard fabric solutions, which means bespoke build-ups and a fuller specification.

What does not change our price is the number of revisions the approver asks for. Responding to plan-check comments is part of the job we were engaged to do, and it is inside the fixed fee.

How long does building control approval take?

The drawings take 14 to 28 working days depending on the package. Once submitted, a Full Plans application must be determined within five weeks, extendable to two months by written agreement with the applicant — and in practice most London plan checks return comments inside three to four weeks, with approval following shortly after the response.

A Building Notice has no approval stage at all: 48 hours’ notice and the builder can start. That is its only advantage, and it is why it suits a re-roof or a window replacement rather than a loft conversion.

The completion certificate is issued after the final inspection, not after the work looks finished. It is the document your solicitor will need at sale, and it will not be issued if inspections were missed at the stages where the work is later covered up — foundations, damp-proof course, structure and insulation before plasterboard.

Building regulation drawing cost questions