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Radiator Regulations UK: Moving, Adding and Replacing Radiators in a Renovation

Radiator regulations in the UK are lighter than most people expect. Moving, adding or swapping a radiator on an existing wet system is not normally notifiable building work, and it does not need a Gas Safe engineer because no gas is involved. The rules bite when the heating system around it changes: replace the boiler and every heated room needs its own thermostatic control, and a new or fully replaced system should be sized to run at a flow temperature of 55°C or lower, which usually means bigger radiators. This page sets out what Approved Document L and Schedule 4 of the Building Regulations 2010 actually say, and how that shapes radiator choices in a London renovation.

Is moving or adding a radiator notifiable?

Usually not. Schedule 4 of the Building Regulations 2010 lists work that does not need a building notice or full plans application. For an existing fixed building service such as a central heating system, it includes replacing any part that is not a combustion appliance, adding an output device and adding a control device. A radiator is an output device, and a thermostatic radiator valve is a control device. So you can move a radiator to a different wall, add one to a new dressing room or swap a tired panel radiator for a column one without telling building control.

Not notifiable is not the same as unregulated. The work should still meet the energy efficiency standards in Part L, and Approved Document L asks for new heating pipework that runs outside the heated space, such as through a loft or a floor void, to be insulated (paragraph 4.24). When a boiler is replaced, any accessible pipes should be insulated too (paragraph 4.25). And the moment the job grows, the picture changes:

• Replacing the boiler is notifiable gas work. A Gas Safe registered engineer must do it and will notify it through their competent person scheme.
• Extending the system into an extension or loft conversion is part of building work that is already notifiable, and building control will look at the heating as part of the Part L assessment.
• Electric radiators fall under Part P. A new circuit, or any work in a bathroom's special location, is notifiable electrical work; our Part P guide explains when.

The boiler replacement rule: controls in every room

Paragraph 5.20 of Approved Document L says that when a heat generator such as a boiler is replaced in an existing home, each room should be given thermostatic room controls that can adjust its heating separately. Paragraph 5.22 sets out three ways to meet it:

1. a thermostat in one room the circuit serves, plus a thermostatic radiator valve (TRV) or similar control on every radiator outside that room
2. a separate room or zone thermostat for each room
3. a networked control on each radiator, such as smart radiator heads

There is one rule that catches people out: a TRV should not be fitted in the same room as the main thermostat, because the two fight each other. Leave that radiator on a lockshield or manual valve. Rooms without heating do not need controls, and two adjacent rooms with similar use, such as a kitchen and utility room, can be treated as one zone.

For a design project this matters more than it sounds. If you are choosing statement radiators for a period house in the same year the boiler is due for replacement, budget for valves that suit the radiator style: traditional brass thermostatic heads exist for column radiators, and smart heads fit most modern valve bodies.

The 55°C rule and why radiators are getting bigger

Under paragraph 5.10, when a wet heating system is newly installed or fully replaced, including the heat source, radiators and pipework, every part should be sized so the system heats the home at a maximum flow temperature of 55°C or lower. Older systems were typically designed for around 70 to 80°C. A radiator gives out less heat at a lower temperature, so to warm the same room it has to be larger, or a different type.

Where there is no room for bigger radiators, the guidance allows the system to be designed for the lowest temperature that still heats the home. But planning for 55°C from the start keeps the door open to a heat pump later and lets a condensing boiler run in its efficient range now. In practice that means:

• double or triple panel radiators, or tall column radiators, where a single panel used to do the job
• a proper room-by-room heat loss calculation instead of sizing by eye; paragraph 5.8 calls for one
• allowing wall space for radiators early in the layout, before joinery and furniture are fixed
• considering underfloor heating, which naturally runs at low temperatures, in kitchens and open-plan spaces; see our underfloor heating regulations page

Only replacing a few radiators on an existing system does not trigger the 55°C rule. It applies to new systems and full replacements.

Boiler efficiency

If the job includes a new gas boiler, Table 6.2 sets the minimum efficiency for wet heating in an existing home at 92%, as defined under the Energy-related Products rules. Almost every condensing boiler on sale meets it. Paragraph 5.9 adds that a combination boiler should be chosen so it can modulate down to the home's typical heating load, which stops an oversized boiler cycling on and off.

Commissioning and the paperwork

When an installer registered with a competent person scheme does notifiable heating work, they must give the building control body notice that the system has been commissioned within 30 days of finishing. You should also receive a completion certificate for the boiler. Keep both with the house documents; buyers' solicitors ask for them. If work was done without one, our page on the regularisation certificate explains the route to put it right.

Bathroom radiators and towel rails

A towel rail plumbed into the central heating is treated like any other radiator. An electric or dual-fuel towel rail is electrical work, and where it sits matters. Bathrooms are divided into zones around the bath and shower, and the closer an electrical item is to water, the stricter the rules on its rating and how it is connected. A dual-fuel rail on a fused spur outside the zones is straightforward; anything inside them needs a qualified electrician. Our bathroom zones guide sets out the distances.

Positioning: what is rule and what is habit

Putting a radiator under a window is a habit from the era of single glazing, when it counteracted cold draughts. There is no regulation requiring it. With modern glazing, a radiator can go wherever it suits the room, as long as it is not boxed in so tightly that the heat cannot circulate and you follow the manufacturer's fixing and clearance instructions. Behind a sofa is the classic mistake: it warms the back of the furniture, not the room. Covers and screens reduce output too, so size up if you plan to use one.

Planning radiators into an interior scheme

Radiators are part of the design, not an afterthought. In a full refurbishment, decide early whether the heating will be replaced, because that sets the 55°C sizing rule and the controls requirement, and both change how much wall space you need. Our building regulations for London renovations page shows how heating fits with the rest of the sign-off process, and you can see how we approach whole-home projects on the Vertigo Interiors homepage.

Sources

Approved Document L, Volume 1: Dwellings (2021 edition incorporating 2023 amendments), paragraphs 5.8 to 5.22, Table 6.2 and Section 8; Building Regulations 2010, Schedule 4.