New and additional radiators

Extra radiators for extensions, loft conversions and cold rooms, sized to the room and piped neatly. What is involved and typical UK costs.

In short: Fitting a new or additional radiator means adding a radiator where there was none, with new pipework teed into the existing heating circuit. It suits extensions, loft conversions, garage conversions and rooms that are always cold. A new radiator in a new position typically costs £300 to £650 in the UK, depending on the pipe run.

Get a free quote

Fixed price, no obligation. We aim to reply the same day.

Adding a radiator is more involved than a straight swap because flow and return pipes have to be run from the nearest suitable point on the heating circuit to the new position. In a typical house that means lifting floorboards, notching joists within safe limits or running pipe neatly along skirting, then making good. The radiator also has to be sized for the room, which in an extension or loft often means a heat loss calculation rather than guesswork.

The other question is whether the boiler and pipework can cope. Most modern boilers have spare capacity for one or two extra radiators, but a large extension or loft conversion can push an older boiler or a microbore system to its limit. Checking the boiler output against the new total heat load before work starts avoids a radiator that is fitted correctly but never gets properly hot.

What is included

Working out the heat output the new room needs
Checking the boiler and pipework can supply the extra load
Planning the pipe route from the nearest suitable connection
Lifting and relaying floorboards or running surface pipe neatly
Fitting the radiator, brackets, TRV and lockshield valve
Draining, refilling and adding inhibitor to the system
Bleeding and balancing so the new radiator heats evenly

Who it is for

Single-storey and two-storey extensions
Loft and garage conversions
Conservatories and garden rooms connected to the house
Rooms that stay cold even with the existing radiator on full
Knock-throughs where one radiator now serves a bigger space

How much does it cost?

As a guide, a new radiator in a new position with up to a few metres of pipework usually costs £300 to £650. Long pipe runs, concrete floors or several new radiators for an extension can take the price higher. See our full cost guide.

How it works

Survey the room

The room size, insulation, windows and outside walls are assessed to set the heat output needed and choose a radiator.

Plan the pipe run

The nearest flow and return pipes are found and a route is agreed, under the floor where possible or neatly along skirting.

Install and connect

The system is drained, new pipework is run and joined in, and the radiator is fixed and connected with new valves.

Refill and balance

The system is refilled with inhibitor, bled and balanced, and the new radiator is checked alongside the others.

New and additional radiators: FAQs

Can my boiler handle another radiator?

Usually, for one or two. Most combi and system boilers are sized with some headroom, and a typical radiator adds roughly 0.5 to 1.5 kW of load. For a large extension or loft conversion, the total heat loss of the house should be compared with the boiler's output, especially if the boiler is old or was sized tightly.

What if I have solid concrete floors?

Pipes cannot simply go under the floorboards, so they are usually run along the surface behind the skirting, boxed in, or brought down from the ceiling or upstairs floor void. Chasing pipes into a concrete floor is possible but messy, and pipes buried in screed should be protected and sleeved.

Do I need building regulations approval for a new radiator?

Adding a radiator to an existing system is not normally notifiable work on its own. In an extension or loft conversion, the heating forms part of the wider building work that building control will look at, and new radiators should have thermostatic controls to meet energy efficiency requirements.

What pipe size is used?

Most UK systems use 15 mm copper or plastic pipe to radiators, with 22 mm for the main runs. Some homes have microbore pipe of 8 or 10 mm, which limits how many radiators a branch can feed. The new pipework is matched to what the system can support.