UK standard · 18th Edition

BS 7671 electrical plan: what your drawing should show

Before an electrician can price a rewire, an extension or a new build, someone has to decide where every socket outlet, switch and lighting point goes — and which final circuit it belongs to. This guide covers what the 18th Edition expects from a domestic installation, and how much of it belongs on the drawing you hand over.

Reading time: 10 min·Updated: September 2026·By Planelico

What BS 7671 actually is

BS 7671 is the British Standard for low-voltage electrical installations, published jointly by the IET and BSI and known as the IET Wiring Regulations. The current issue is the 18th Edition, BS 7671:2018 as amended by Amendment 2 in 2022.

It is a standard, not a statute. Its authority comes from the fact that regulators, insurers, certification bodies and the courts all treat compliance with it as the normal way of showing that an installation is safe. Under Part P of the Building Regulations in England and Wales, electrical work in dwellings has to meet it.

What this means for your plan: BS 7671 tells you how the installation must be designed and protected. It does not tell you how many sockets a bedroom needs, and it does not dictate a drawing format. Those are yours to decide — which is precisely why a clear layout drawing is worth the effort.

What the drawing should show

An electrician quoting from a vague sketch will price defensively, and the variations will arrive later. A drawing that answers the following six questions removes most of that risk.

Every accessory, positioned

Socket outlets, switches, lighting points, fused connection units, data outlets and the appliances that need a dedicated supply.

Circuit identity

Which way in the consumer unit each accessory belongs to. A drawing without circuit grouping cannot be priced properly.

The consumer unit

Its location, and a schedule of the ways with device types and ratings.

Mounting heights

Where they differ from the default — worktop sockets, high-level TV points, accessible-height switches.

Special locations

Bathroom and shower-room zones, outbuildings, anything outdoors.

Notes for the electrician

Anything the drawing cannot express: existing cabling to reuse, phasing, finishes, access constraints.

Typical final circuits in a UK dwelling

These are the arrangements you will see on most domestic jobs. Ratings and cable sizes below are the common starting points — the actual design depends on the load, the cable route, grouping, insulation and the length of the run, which is the designer's calculation, not a lookup.

Circuit	Typical protective device	Typical cable	Notes
Ring final circuit (sockets)	32 A	2.5 mm² twin & earth	Serves a floor or a zone; both legs return to the same way in the board.
Radial socket circuit	20 A	2.5 mm² twin & earth	Simpler to design and to test; common for kitchens, garages and extensions.
Lighting circuit	6 A	1.0 or 1.5 mm²	Usually one per floor; 1.5 mm² where runs are long or loading is heavy.
Cooker / oven	32 A or 40 A	6 mm²	Sized on the appliance rating with diversity applied.
Electric shower	40 A or 45 A	10 mm²	Depends on the shower kW rating and the cable route and grouping.
Immersion heater	16 A	2.5 mm²	Dedicated circuit with a local double-pole switch.
EV charge point	32 A	6 mm²	Dedicated circuit; also subject to BS 7671 Section 722.

Not a design tool: treat this table as vocabulary for talking to your electrician, not as a specification. Cable sizing, disconnection times and earth fault loop impedance all have to be calculated and verified for the actual installation.

RCD and RCBO protection

Additional protection by a 30 mA RCD is required for socket outlets rated up to 32 A in domestic premises, and for cables concealed in walls at a depth of less than 50 mm where they are not otherwise mechanically protected. In practice, that covers almost everything in a house.

That leaves the question of how the protection is arranged. A split-load board puts circuits behind two 30 mA RCDs, which is cheaper but means one fault takes out half the house. A full RCBO boardgives each circuit its own combined overcurrent and residual-current device, so a fault isolates a single circuit. The second has become the default on new work, and it is worth stating which you want before quotes come in.

Amendment 2 also brought AFDDs (arc fault detection devices) into the picture — required for socket outlet circuits in certain higher-risk residential buildings, and recommended more broadly — and made surge protection the default position for dwellings unless a risk assessment concludes otherwise.

Bathrooms and other special locations

Section 701 of BS 7671 divides a bathroom or shower room into zones measured from the bath or shower, and restricts what may be installed in each, along with the IP rating equipment must achieve. Socket outlets are excluded from the zones altogether and must sit at a distance from the bath or shower, the usual exception being a shaver supply unit to BS EN 61558-2-5.

Outbuildings, garden supplies, garages and EV charge points each carry their own requirements. Mark them clearly on the plan: they change the cabling, the protection and often the price.

Drawing bathroom zones as coloured areas on the floor plan is one of the fastest ways to make a layout readable. The constraint becomes visible instead of living in a note at the bottom of the page.

Part P, notification and certification

In England and Wales, Part P of the Building Regulations makes electrical safety in dwellings a building-control matter. Certain work is notifiable: installing a new circuit, replacing a consumer unit, and work in special locations such as bathrooms. Notifiable work has to be done by an installer registered with a competent person scheme, who self-certifies it, or else notified to building control in advance.

On completion you should receive an Electrical Installation Certificatefor new work, or a Minor Electrical Installation Works Certificate for smaller alterations. Keep it: it is what a buyer's solicitor will ask for, alongside the most recent EICR for the property.

Scotland and Northern Ireland handle building control differently, and the Republic of Ireland works to I.S. 10101 with its own certification through Safe Electric. The wiring practice is close; the paperwork is not.

Drawing the layout in Planelico

Planelico works on top of the PDF you already have. You are not redrawing the building — you are annotating it with the electrical layout, then exporting something an electrician can price.

1
Import your floor plan as a PDF
An architect drawing, a surveyor plan or even a clean scan. It becomes a background layer you annotate without altering the original.
2
Place accessories room by room
Drag socket outlets, switches, lighting points, data outlets and appliance supplies onto the plan, using the IEC 60617 symbol set.
3
Group them into circuits
Assign each accessory to a final circuit so the drawing shows the intended circuit split, not just a scatter of symbols.
4
Mark the special locations
Draw zones for bathrooms, shower rooms and outbuildings so the constraints are visible at a glance.
5
Export the PDF for pricing
A clean document with legend, per-room summary and title block — the thing an electrician can actually quote from.

The symbol library follows IEC 60617, adopted in the UK as BS EN 60617 — the same graphical conventions used on British electrical drawings. See the electrical symbols reference, the consumer unit diagram guide, or the guide to preparing a plan for a quote.

Frequently asked questions

Is BS 7671 a legal requirement in the UK?

BS 7671, the IET Wiring Regulations, is not itself a statutory instrument — it is a British Standard. In practice it is the recognised way of demonstrating compliance with the Electricity at Work Regulations and with Part P of the Building Regulations, so installations are designed and certified to it as a matter of course.

How many socket outlets does BS 7671 require per room?

It does not set a minimum count. This surprises people who have seen French or Belgian rules, where per-room minimums are prescribed. In the UK the number is a design decision, guided by how the room will be used; Approved Document M does govern the mounting height of accessories in new dwellings, typically between 450 mm and 1200 mm above finished floor level.

Ring final circuit or radial — which should I plan for?

Both are permitted. A 32 A ring on 2.5 mm² covers a large floor area with less cable, while 20 A radials are simpler to design, test and fault-find, and are increasingly specified on new work. It is a decision for the designing electrician; your drawing should show which one you have assumed so the quote matches.

Do I need an electrician, or can I do the work myself?

You can plan the layout yourself — that is exactly what this kind of drawing is for. The installation, testing and certification are another matter: notifiable work under Part P must be carried out by a registered competent person or signed off by building control.

Does this guide apply in Scotland and Northern Ireland?

BS 7671 applies across the UK and in the Republic of Ireland the equivalent is I.S. 10101. The building-control side differs: Part P is an England and Wales instrument, Scotland works through its own Building Standards, and Northern Ireland has its own regulations. Check the route that applies where you are building.

Draw your electrical layout on your own floor plan

Import the PDF, place the accessories, group them into circuits and export a document your electrician can quote from.

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