BS EN 1264 and BS 7671 in plain English for underfloor heating

Installers, designers and building control officers refer to these two standards constantly, but few homeowners have read them. Both are paid-for documents. This guide explains in plain English what each one covers, which parts matter for an underfloor heating job, and how they link to the Building Regulations.

It is a summary, not a substitute for the standards themselves. Where we give a requirement, we say where it comes from. For the energy rules in Part L, see our guide to Part L and the Future Homes Standard.

What are BS EN 1264 and BS 7671?

BS EN 1264 is about the water side of underfloor heating. BS 7671 is about the electrical side of any installation. A water UFH job touches both, and an electric UFH job is covered mainly by BS 7671.

Neither standard is law on its own. They matter because the Building Regulations guidance, contracts, maker warranties and certification schemes point to them. For electrical work in homes in England, Approved Document P says installations should be designed and installed in accordance with BS 7671.

What are the five parts of BS EN 1264?

BS EN 1264 is split into five parts. All five were republished in 2021 and replaced the earlier editions, which BSI lists as withdrawn.

The series covers water based heating and cooling built into floors, walls and ceilings, in homes and other buildings. It does not cover suspended ceilings with an open air gap.

What does BS EN 1264 mean for design?

Parts 2 and 3 are what turn a heat loss figure into pipe centres, flow temperatures and loop lengths. Part 2 sets out how the heat output of a floor system is calculated and tested, so that outputs from different makers can be compared fairly.

Part 3 applies those results to real projects. In plain terms, it says:

• Floor surface temperature is limited for comfort. BSI describes the heating limits as physiological. For floor heating they are applied through the characteristic and limit curves from Part 2. Our guide to UFH thermostats gives the commonly quoted figures.
• Room size and layout affect the design. A design that ignores them can stop the system working properly.
• Pressure loss must be considered. The 2021 edition added sections on pressure loss, which is why long loops and the pump's ability to push water round them are part of the design.
• Dimensions can be adjusted. The standard gives general dimensions that can be adapted to a project's specification.

When a supplier quotes a floor output in W/m², ask whether it was worked out to BS EN 1264-2, and at what flow temperature and floor covering. Our guide to UFH heat output shows how to check whether a floor will heat a room.

What does BS EN 1264-4 mean on site?

Part 4 is the installer's part. BSI lists its topics as hydronic balancing, the supporting base and other layers, insulating layers, the weight-bearing layer, damage to the pipe, the leak test, and the initial heat-up before the floor is ready for covering, with an initial heating-up protocol in Annex B.

MaxHeatUFH tests every floor at 6 bar for 60 minutes before screeding, and keeps the pipe under pressure while the screed goes down, so damage shows straight away. Record the test with the date, time and pressure. The step-by-step sequence is in our guide to installing water underfloor heating.

The initial heat-up proves the system works. It is not a test that the screed is dry enough for the floor finish, which the floor layer checks separately.

What is BS 7671 and which edition applies now?

BS 7671 is the national standard for electrical installations in the UK, published by the IET with BSI and known as the IET Wiring Regulations. The IET says BS 7671:2018+A4:2026, Amendment 4, is now the current edition, and that the transition period for Amendment 2 ended on 15 October 2026.

Approved Document P still names an older edition, BS 7671:2008 with Amendment 1, because the approved document itself dates from 2013. Electricians work to the current edition. If you are getting quotes, check that the installation certificate will be issued to BS 7671:2018+A4:2026.

Part 7 of BS 7671 holds the rules for special installations or locations. Two sections matter most for underfloor heating:

• Section 701: locations containing a bath or shower. Covered in our guide to electric UFH in bathrooms.
• Section 753: floor and ceiling heating systems, extended in the 18th edition to embedded electric heating more widely.

Which parts of BS 7671 matter for water underfloor heating?

On a water system, the electrics are the wiring centre, room thermostats, actuators, pump and heat source link. These are ordinary circuits under BS 7671, and the maker's instructions add their own conditions.

• The Heatmiser UH8 manual says the mains supply to the wiring centre should be fused at 5A, and the board has a 5A anti-surge fuse feeding its 230V outputs.
• Each zone relay on the UH8 is rated 3A resistive, with a 5A total load.
• The boiler link on the UH8 is a volt-free contact.

Whether the work must be notified to building control depends on what is done, not on the heating type. See the section on Part P below. Wiring should be done by a qualified electrician. Our guide to zoning and wiring centres explains the layout.

What does BS 7671 Section 753 require for electric underfloor heating?

Section 753 covers heating cables and mats built into floors and ceilings. IET guidance on Section 753, written by its chief engineer, sets out these requirements:

• RCD protection. Heating units without exposed conductive parts need a metallic grid with spacing of no more than 30mm, connected to the protective conductor, and protection by an RCD of 30mA or less. Class II heating units need additional protection by an RCD of no more than 30mA.
• Embedded in concrete or similar. Floor heating units need at least IPX7 and suitable mechanical properties.
• Temperature limits. Where skin or footwear can touch the floor, its surface temperature must be limited, with 35°C given as an example. The heating zone must be limited to 80°C by design, installation or protective devices.
• Heating-free areas. Areas where screws or nails may be driven must be kept free of heating units, and other trades must be told.
• Connections. Heating units connect through cold tails or suitable terminal fittings, inseparably joined, and must not cross expansion joints.
• Documentation. The installer must provide a plan with details such as the maker and type, rated power, surface power density, layout, cold resistance, protective device ratings and insulation resistance, fixed at or near the heating distribution board.
• User information. The owner must get a description of the system and instructions for use, including restrictions on furniture, coverings and fixings into the floor.

The IET article was written for an earlier edition, and the 18th edition extended Section 753. Your electrician should check each point against BS 7671:2018+A4:2026.

Do I need to notify building control?

Under Part P in England, electrical work in a home is notifiable if it is a new circuit, a replacement consumer unit, or an addition or alteration to existing circuits in a special location, such as the space around a bath or shower. Other work is not notifiable, but must still be done safely and in line with BS 7671.

Notifiable work is certified in one of three ways: by an electrician registered with a competent person scheme, by a registered third party certifier appointed before work starts, or through your building control body.

Products for this job

Prices include VAT, October 2026.

• Hydraulic Pressure Test Pump, for the leak test: £114
• Heatmiser UH8 8 Zone Wiring Centre: £77
• 2-Wire Thermal Actuator 230V: £12
• Heatmiser neoStat-e electric floor thermostat, switches up to 16A: £83
• MaxHeatUFH loose heating cable, twin core with earth screen: from £14
• Edge Insulation Roll 50m: £17
• All water underfloor heating

Related guides: How to install water underfloor heating and Underfloor heating thermostats explained.

Frequently asked questions

Is BS EN 1264 a legal requirement?

Not on its own. It is a standard, not a law. It becomes binding when a contract, specification or warranty calls for it. Makers and designers use it as the common reference for rating, designing and installing water UFH.

What is the current edition of BS 7671?

BS 7671:2018+A4:2026, Amendment 4 to the 18th edition. The IET says it is now the current edition.

Does electric underfloor heating need an RCD?

Yes. IET guidance on Section 753 requires RCD protection of 30mA or less for floor heating units, and bathrooms have their own rule requiring 30mA RCD protection for all circuits.

Can I fit electric underfloor heating myself?

You can lay a mat or cable yourself, but a qualified electrician should make the final connection and test it. A new circuit, or any work in a bathroom special location, is notifiable under Part P.

What test does BS EN 1264-4 require before screeding?

Part 4 includes a leak test procedure. MaxHeatUFH tests at 6 bar for 60 minutes and keeps the system under pressure while the screed is laid.

Do I need to give the homeowner paperwork for electric UFH?

Yes. The IET guidance on Section 753 requires a plan of the installation fixed at or near the distribution board, plus a description and instructions for the owner, including where fixings must not go.

Sources: BSI: BS EN 1264-4:2021, BSI: BS EN 1264-2:2021, BSI: BS EN 1264-3:2021, BSI: BS EN 1264-5:2021, IET: Amendment 4 updates, IET Wiring Matters: floor and ceiling heating, IET: 18th edition Sections 722, 753 and 730, Approved Document P (gov.uk), Heatmiser UH8 manual