Underfloor Heating Explained: Benefits, Materials, Pipe Calculations, Zoning, and How to Choose the Right System

Underfloor heating is one of the cleanest ways to heat a home, extension, bathroom, kitchen, or open-plan living space. Instead of pushing heat out from a small radiator area, it spreads heat gently across the floor surface, giving a more even room temperature, better comfort underfoot, and more freedom on wall space.

At APM Plumbing & Electrical in Acton, West London, we supply practical underfloor heating products for both installers and homeowners, including UFH manifolds, UFH pipe, electric underfloor heating mats, thermostats, and isolation valves. This guide explains the main benefits of underfloor heating, the key components you need, how to estimate pipe quantities, how to split the system into zones, and how to choose the right materials for the job.

Why choose underfloor heating?

• Better comfort: heat is spread more evenly across the room rather than concentrated around one radiator.
• Lower flow temperatures: wet underfloor heating usually works efficiently with lower water temperatures than standard radiators, which suits modern boilers and heat pumps.
• Cleaner room layout: no radiators means more usable wall space for furniture, kitchens, bathrooms, and open-plan rooms.
• Gentle, even heat: less hot-and-cold variation across the room.
• Good option for extensions and refurbs: especially where a new floor build-up is already planned.
• Can be zoned well: different rooms or areas can run at different temperatures and times.

In the right build-up, underfloor heating can feel more comfortable than radiators because the floor becomes the heat emitter. That is especially useful in bathrooms, kitchens, tiled areas, and large family spaces.

Wet underfloor heating vs electric underfloor heating

1. Wet underfloor heating

This uses warm water running through pipe loops in the floor. It is usually the better choice for:

• whole-house systems
• extensions
• ground floors
• larger heated areas
• projects using a heat pump or low-temperature heating design

2. Electric underfloor heating

This uses electric mats or cable systems under the finished floor. It is usually simpler for:

• single bathrooms
• ensuites
• small kitchens
• retrofit projects where pipe build-up is harder to achieve
• areas needing quick installation

The right system depends on the floor construction, available height, heat source, running cost expectations, and whether the job is a single room or a full-property install.

Main components for a wet underfloor heating system

For a standard water-based UFH system, these are the main components to think about:

• UFH pipe – usually multilayer or PERT-AL-PERT / PEX-AL-PEX pipe
• Manifold – the distribution point that feeds each loop or zone
• Manifold isolation valves – useful for servicing and isolation
• Pump / mixing arrangement – depending on system design and heat source
• Thermostats and controls – room-by-room or zone-by-zone control
• Wiring centre / actuators – for multi-zone control systems
• Insulation boards or insulation layer – essential to push heat upward, not down into the slab
• Edge insulation – allows for expansion and reduces heat loss at the perimeter
• Fixing system – staples, rails, trays, castellated panels, or clip-rail systems
• Screed or overlay board system – depending on floor build-up

KeyPlumb UFH 5 Port Manifold Underfloor Heating UK is one example of the type of manifold used when several loops need to be controlled from one location.

Main components for an electric underfloor heating system

• Heating mat or loose cable
• Thermostat with floor sensor
• Insulation boards where suitable
• Flexible tile adhesive / levelling compound depending on floor finish
• RCD-protected electrical connection and correct installation to regulations

For smaller rooms, products like the eZheat 560W 3.5m² Electric Underfloor Heating Mat UK and the Electric Underfloor Heating Thermostat Control UK can be a practical route.

What materials do you need under the floor?

The exact floor build-up depends on whether the job is a new screed floor, a retrofit overlay, or an electric mat installation. In general, you should think in layers:

1. Structural floor – concrete slab or timber deck
2. Insulation – to limit downward heat loss
3. UFH fixing layer – staples, trays, castellated panels, grooved boards, or rails
4. Pipe or electric mat
5. Screed / levelling layer / overlay panel
6. Final floor finish – tile, stone, vinyl, engineered wood, laminate, etc.

Good insulation is critical. If the insulation is poor, the system wastes energy heating the structure below instead of the room above.

How do you calculate how much UFH pipe you need?

This is one of the most common questions. A simple estimating method is:

Pipe length ≈ heated floor area ÷ pipe spacing

Then add an allowance for the tails to and from the manifold and a little contingency.

Common pipe spacing guide

• 100mm centres – higher heat output areas or where losses are higher
• 150mm centres – common for many domestic rooms
• 200mm centres – lighter heat demand areas with better insulation

Example calculation

Say the heated floor area is 20m² and the design uses 150mm spacing:

• 20 ÷ 0.15 = 133m of pipe
• Add roughly 10% for tails / layout allowance = about 146m

That would usually be too long for one loop, so it would normally be split into two loops of roughly 73m each.

Typical loop length guide

• 12mm pipe – often kept around 60m to 80m per loop depending on design
• 16mm pipe – often around 80m to 100m per loop depending on pressure drop and output target

These are practical rules of thumb, not a substitute for a full heat-loss and pressure-drop design. Final loop lengths should always follow the manufacturer’s design guidance and the project heat requirements.

If you need pipe for smaller loops or compact installations, a product like Keyplumb Multilayer UFH 80m 12mm Pert-Al-Pert Coil - Boxed UK is a useful example. For larger jobs, longer coil options such as Multilayer Pert-Al-Pert UFH Pipe 200m 16mm x 2mm - Boxed UK can make more sense.

How do you divide underfloor heating into zones?

Zoning matters because different rooms heat up and cool down differently. A good UFH system should not treat every room the same.

You would normally think about separate zones based on:

• room use – bathroom, bedroom, kitchen, open-plan living area
• orientation and solar gain – south-facing rooms can behave very differently
• floor finish – tiles, timber, carpet and vinyl all affect output
• heat loss – external walls, glazing, doors, and insulation levels
• time schedule – bathrooms and living spaces may need different operating times
• loop length practicality – large spaces may need multiple loops even within one zone

Simple zoning example

• Zone 1: kitchen / dining / family room
• Zone 2: lounge
• Zone 3: hallway
• Zone 4: bathroom

That does not always mean one loop per room. A large open-plan space may need two or three loops but still operate as one control zone. Meanwhile a bathroom often benefits from its own zone because people usually want it warmer than a bedroom or hall.

Where the manifold is used, the number of ports matters. APM stocks different sizes such as:

• KeyPlumb UFH 4 Port Manifold Underfloor Heating UK
• KeyPlumb UFH 5 Port Manifold Underfloor Heating UK
• Keyplumb UFH 7 Port Manifold Underfloor Heating UK
• Keyplumb UFH 8 Port Manifold UK

For servicing and isolation around the manifold, KeyPlumb UFH 1" Isolation Ball Valve - Pair UK is also worth considering.

How do you choose the right pipe size and material?

Pipe choice usually depends on the system design, floor build-up, loop length, and heat output target.

• 12mm pipe – useful where tighter floor build-up or smaller loops are needed
• 16mm pipe – common for many domestic wet UFH systems
• Multilayer / Pert-Al-Pert / PEX-AL-PEX – helps the pipe hold shape and suits UFH applications well

Material choice should also match the manufacturer’s fittings, bending radius, oxygen barrier requirements, and the intended manifold / control setup.

How do you choose the right thermostat and controls?

Controls should match the type of UFH system and how the customer wants to use the space.

• Basic room thermostat – for simple control
• Programmable thermostat – for time and temperature scheduling
• Floor sensor thermostat – especially useful with electric UFH and sensitive floor finishes
• Multi-zone smart controls – better for larger or more premium wet UFH systems

For electric UFH, a product like the Devi DEVIreg 530 Underfloor Heating Thermostat with Floor Sensor is a good example of a dedicated control option.

Best floor finishes for underfloor heating

Some floor finishes pass heat better than others.

• Tiles and stone – usually excellent because they conduct heat well
• Engineered wood – often suitable if manufacturer-approved for UFH
• Vinyl / LVT – often suitable within temperature limits
• Laminate – can work if rated for UFH
• Carpet – possible, but total tog value matters and can reduce output

Always check the floor finish manufacturer’s maximum surface temperature and underfloor heating compatibility.

Practical buying checklist

Before ordering, it helps to work through this list:

1. Measure the true heated area after deducting fixed units, baths, showers, islands, and permanent furniture where applicable.
2. Decide whether the job needs wet UFH or electric UFH.
3. Choose the pipe spacing or mat size based on heat demand and floor build-up.
4. Estimate total pipe length and split it into sensible loops.
5. Select the correct manifold port count.
6. Choose suitable controls and zoning.
7. Confirm the final floor finish is UFH-compatible.
8. Check that insulation, fixing method, and screed / overlay system all work together.

Shop underfloor heating materials from APM

If you are planning an underfloor heating job, APM can help you source the practical items that matter most, including:

• UFH manifolds
• UFH pipe coils
• manifold isolation valves
• electric heating mats
• electric UFH thermostats
• floor-sensor thermostats

Visit us at APM Plumbing & Electrical, 24 Western Avenue, Acton, London W3 7TZ, or shop online at apmi.uk. If you need help choosing the right manifold size, pipe coil, or thermostat for your layout, contact the APM team before ordering.

Important: the examples above are practical estimating guidance only. Final underfloor heating design should always be checked against room heat loss, floor construction, floor covering limits, and the manufacturer’s technical guidance before installation.