New ground floors
In-Screed Water Heating
A strong starting point when the extension includes a new slab and screed, particularly for larger open-plan ground-floor spaces.
Room & project guide
Underfloor Heating For Extensions
Choose a heating route that suits the new floor construction, available build-up and the way your extension will connect to the rest of the home.
Start with the floor
Which Part Of The Extension Are You Heating?
The right solution is driven by the construction—not simply the room name. Choose the route that most closely matches your planned floor.
New ground floors
View In-Screed Solutions
Existing base floor
Low-Profile Retrofit Systems
Overlay water heating or electric heating can suit projects where the structural floor is already in place and build-up must be controlled.
Upper floors
Timber & Joisted-Floor Systems
Lightweight water systems for first-floor extensions and suspended timber constructions where a full screed is not suitable.
Compare The Three Approaches
| Comparison criteria | In Screed | Retrofit | Joisted Floors |
|---|---|---|---|
| Starting point | New slab or structural screed | Suitable existing structural floor | Timber or engineered joists |
| System position | Pipe embedded within the screed | Above the base and beneath the finish | Between or across the joists |
| Main priority | Efficient heating across a new floor area | Reduced disruption and controlled height | Low weight with a compatible floor build-up |
In Screed
- Starting point
- New slab or structural screed
- System position
- Pipe embedded within the screed
- Main priority
- Efficient heating across a new floor area
Retrofit
- Starting point
- Suitable existing structural floor
- System position
- Above the base and beneath the finish
- Main priority
- Reduced disruption and controlled height
Joisted Floors
- Starting point
- Timber or engineered joists
- System position
- Between or across the joists
- Main priority
- Low weight with a compatible floor build-up
Electric alternatives
Prefer Electric Heating For Your Extension?
Electric heating can be a practical route for a self-contained room or where extending the water system is not appropriate. Match the system to the floor construction first.
Existing-floor electric option
MD Electric Heating Mats
Pre-spaced electric heating for regular-shaped extension floors
- Quick cut-and-turn layout across clear floor areas
- Available in 100W, 160W and 200W outputs
- Suited to compatible tiled floors and approved covered build-ups
- The usable heated area and output must be confirmed before ordering
New screed electric option
VCD17 In-Screed Heating Cable
An electric cable installed within a planned screed floor
- Designed for extensions with a new screed floor
- Flexible cable layout across larger open areas
- Planned with suitable insulation and the complete floor build-up
- Final output and spacing confirmed against the room heat loss
Plan the complete extension
Four Details To Confirm Before You Choose
If water underfloor heating will connect to an existing heating system, the heat source, hydraulic design and controls must be checked as part of the project design.
Floor Construction
Confirm whether the extension is screeded, timber joisted or built over an existing structural floor
Heat Source Capacity
For water heating, confirm that the boiler or heat pump and controls can support the additional load
Levels & Insulation
Plan insulation and finished floor heights where the extension meets the existing building
Heat Loss & Zoning
Calculate room heat loss and decide whether the extension needs its own controllable heating zone