Two of the UK's best loose lay electric underfloor heating systems go head to head
If you are specifying or buying a loose lay electric underfloor heating cable with a decoupling membrane in the UK, the shortlist almost always comes down to two names: the ThermoSphere Ultimate heating cable and membrane and the Warmup DCM-PRO system. Both pair a flexible heating cable with a castellated decoupling mat, both are aimed squarely at tiled floors in bathrooms, kitchens and renovations, and both are backed by lifetime cable warranties when installed correctly.
The differences sit in the details: cable construction, joint technology, output options, membrane design and the warranty small print. In this expert guide we compare both systems for installers and homeowners, run the ThermoSphere T-MO against the Warmup 7iE smart thermostat, and explain why you can happily mix and match the two brands in one installation.
What is electric underfloor heating with a decoupling membrane?
Electric underfloor heating uses a resistive heating cable installed beneath your floor finish. When current passes through the cable it generates gentle, even radiant warmth across the whole floor area, controlled by a thermostat with a floor temperature probe. Unlike a wet (water-based) system there are no pipes, manifolds or boiler connections, which makes electric the natural choice for single rooms, bathrooms and renovation projects where build-up height matters. You can read more fundamentals in our underfloor heating buying guide.
A loose lay decoupling system takes this one step further. Instead of a fixed mat with cable pre-spaced on mesh, the heating cable is pressed by hand into the round castellations (studs) of a polypropylene membrane. This brings two major advantages. First, complete layout freedom: you route the cable exactly where you want heat, around toilets, baths, vanity units and irregular room shapes, and you change the cable spacing to fine-tune the heat output. Second, the membrane itself acts as a decoupling layer, absorbing lateral subfloor movement so that seasonal expansion, contraction and minor substrate cracking never transfer stress into your tiles and grout.
How the system goes together
Prepare and insulate
Clean, level subfloor, ideally topped with insulated tile backer board to cut heat-up times and running costs.
Fix the membrane
Peel-and-stick or adhesive-fixed decoupling membrane is laid over the floor area, trimmed around obstacles with a knife.
Lay the cable
The heating cable is pressed into the membrane studs by hand, no tools needed, at the spacing your heat-loss calculation requires.
Test, cover, tile
Resistance and insulation tests, then flexible tile adhesive or self-levelling compound, floor finish, and thermostat commissioning by a qualified electrician.
Advantages of loose lay decoupling underfloor heating
Tile crack protection built in
The decoupling membrane isolates the tile bed from subfloor movement, dramatically reducing the risk of cracked tiles and failed grout joints, the most common tiled-floor failure in UK homes.
Total layout freedom
Unlike fixed mats, the cable goes exactly where you want it. Heat the walkable floor area only, skip under fitted units, and adapt to awkward room shapes without wasting cable.
Adjustable heat output
Change the cable spacing in the membrane studs to dial the output up or down, from gentle floor warming to a full primary heat source for the room.
Minimal build-up height
At roughly 4.5 to 6mm total system thickness before tile adhesive, these systems suit renovations where door thresholds and floor levels are fixed.
No maintenance, no moving parts
No pumps, valves or annual servicing. A correctly installed cable simply works, silently, for the life of the floor, which is why both brands offer lifetime cable warranties.
Room-by-room efficiency
Each room runs on its own thermostat and schedule, so you only heat the spaces you use. Paired with solar PV or off-peak tariffs, running costs drop further.
ThermoSphere Ultimate vs Warmup DCM-PRO: the key differences
Both systems share the same basic architecture, a loose lay heating cable clipped into a castellated decoupling membrane, so the real comparison is in cable engineering, output flexibility and guarantees.
Cable construction and the joint question
ThermoSphere Ultimate is the only heating cable on the market that combines TwistedTwin construction with in-line joint technology. The twisted-pair conductors neutralise mechanical stress along the cable, while the in-line hot-to-cold joint means the cable is the same slim profile from end to end. There is no bulky factory joint to bury, so you never need to cut into the membrane or the subfloor to conceal it, removing the single most common point of installation damage and long-term failure. Installation of the joint area becomes a one-step, tool-free process.
Warmup DCM-PRO uses a 4.5mm multi-strand, dual-core cable insulated with an advanced ETFE fluoropolymer inner jacket and a smooth PVC outer sleeve, making it exceptionally tough, flexible and easy to tile over. It clips cleanly into the DCM-PRO membrane castellations with thumb pressure, and the membrane protects the secured cable from damage during installation.
Heat output options
The ThermoSphere Ultimate cable delivers 130W/m² or 195W/m² depending on whether you space the cable at two or three studs, covering everything from background floor warming to primary heating. Warmup's DCM-PRO standard cable spans 112.5 to 225W/m² through 60mm, 90mm and 120mm spacing options, and Warmup additionally offers a dedicated low-wattage cable (41.3 to 82.5W/m²) for highly insulated homes and properties with restricted electrical supplies, a genuinely unique option in the UK market.
Membrane and compatibility
Warmup's DCM-PRO membrane is one of the most heavily tested on the market, successfully tested to the American ANSI 118.12 crack-isolation standard, with a self-adhesive peel-and-stick underside that acts as a self-healing decoupling layer and saves a full adhesive step. Warmup claims installation up to 40% faster than standard membranes. ThermoSphere's membrane is likewise self-adhesive with a waterproof construction suited to wet rooms.
Crucially for installers, ThermoSphere Ultimate cable is officially compatible with popular third-party decoupling mats, including Warmup's DCM-PRO membrane, so you can run your preferred cable in your preferred mat.
Warranties and guarantees
Both cables carry lifetime warranties when installed and registered correctly. The headline difference is ThermoSphere's guaranteed reliability promise: if the system fails within the first 12 months due to a manufacturing fault, ThermoSphere will replace not just the heating system but the floor covering too. Warmup counters with its SafetyNet installation guarantee: accidentally damage the heater during installation and Warmup replaces it with the same make and model, plus a lifetime warranty on the cable when installed with the DCM-PRO mat.
| Feature | ThermoSphere Ultimate | Warmup DCM-PRO |
|---|---|---|
| Cable construction | TwistedTwin twisted-pair with continuous earth | Multi-strand dual core, ETFE inner, PVC outer |
| Hot/cold joint | In-line joint, same profile end to end, no cutting in | Conventional joint, conceal within floor build-up |
| Heat output | 130W/m² or 195W/m² (2 or 3 stud spacing) | 112.5–225W/m² (60/90/120mm); low-wattage cable 41.3–82.5W/m² |
| Cable thickness | Slim profile throughout, incl. joint | 4.5mm (±0.2mm) |
| Membrane | Self-adhesive, waterproof decoupling membrane | Peel-and-stick, self-healing layer, ANSI 118.12 tested |
| Third-party mat compatibility | Yes — works in DCM-PRO, Ditra and other popular mats | Cable designed for DCM-PRO membrane |
| Headline guarantee | 12-month guaranteed reliability incl. floor covering replacement | SafetyNet installation guarantee |
| Cable warranty | Lifetime (registered, with compatible thermostat) | Lifetime (with DCM-PRO mat) |
| Made in | Great Britain | P.R.C. |
Our verdict: for outright cable reliability and the easiest joint handling on site, ThermoSphere Ultimate edges it, and its floor-replacement guarantee is unmatched. For the widest output flexibility, including the UK's only low-wattage decoupling option, and the most proven membrane, Warmup DCM-PRO remains the benchmark. Either way you are buying a premium system; the right choice depends on your project's heat-loss figures, supply capacity and your preferred workflow.
Thermostat face-off: ThermoSphere T-MO vs Warmup 7iE
The thermostat decides how efficiently your floor actually runs day to day, so it deserves as much attention as the cable. Both of these flagship controls handle any direct electric heating load up to 16A and use a floor probe for accurate, safe floor temperature control. See our thermostat buying guide for the full background.
The ThermoSphere T-MO is built installer-first: push-fit mounting, a crisp LED segment display that can switch fully off at night, Wi-Fi plus Bluetooth setup through the T-MO app, active power and energy metering, and ZeroX technology that switches the relay at zero volts to extend its service life. Clever extras include copy-and-paste schedules across days and thermostats, DirectLink wireless linking between multiple T-MOs, a relay mode for electric towel rails, an open API for building management integration and over-the-air updates. It carries a 5-year warranty.
The Warmup 7iE is the world's first floor heating thermostat with native Matter protocol support, meaning it drops straight into Apple Home, Google Home or Amazon Alexa with no bridges or workarounds. Its vivid colour touchscreen, premium finishes (Bright Porcelain or Onyx Black) and the MyHeating app's intelligent features make it the most polished smart-home experience in floor heating.
| Feature | ThermoSphere T-MO | Warmup 7iE |
|---|---|---|
| Display | 14-segment LED, full off in standby | Full colour touchscreen |
| Connectivity | Wi-Fi + Bluetooth LE | Wi-Fi + native Matter |
| Smart home | T-MO app, open API for BMS | Apple Home, Google Home, Alexa via Matter |
| Energy insight | Active power + energy metering | Energy monitoring in MyHeating app |
| Installer features | ZeroX relay protection, DirectLink, copy-paste schedules, relay mode for towel rails, OTA updates | SmartGeo-style intelligent scheduling, premium trims |
| Max load | 16A | 16A |
| Warranty | 5 years | Extended Warmup warranty |
| Price at AIZO | £149.00 inc. VAT | £195.00 inc. VAT |
Which to choose? If you live in the Apple, Google or Alexa ecosystem and want the slickest touchscreen on the wall, the 7iE is in a class of one thanks to Matter. If you value energy metering, installer-friendly commissioning, multi-room linking and a lower price, the T-MO is exceptional value at £149.
Yes — you can mix and match the two brands
This is the part many buyers miss: electric underfloor heating cables and thermostats are not locked to their own brand. Any quality thermostat rated for your system's load (both the T-MO and 7iE switch up to 16A) and compatible with common NTC floor probes will run either cable system.
That means you can pair a Warmup 7iE thermostat with a ThermoSphere Ultimate cable to get Matter smart-home control over Britain's most reliable heating cable, or run a ThermoSphere T-MO on a Warmup DCM-PRO system for energy metering at a friendlier price. You can even lay ThermoSphere Ultimate cable directly into Warmup's DCM-PRO membrane, since the cable is officially compatible with popular third-party decoupling mats. One practical note: always confirm the floor sensor type during commissioning and register each product with its manufacturer to keep the warranties intact.
Shop the systems compared in this guide
ThermoSphere
Ultimate Loose Lay Underfloor Heating Cable
The only cable combining TwistedTwin construction with an in-line joint. 130W/m² or 195W/m² outputs, tool-free installation and ThermoSphere's guaranteed reliability promise including floor covering replacement.
From £13.95 inc. VAT
Warmup
DCM-PRO Electric UFH System — Cable & Mat
The world's best-selling heated decoupling system. ETFE-insulated 4.5mm cable, peel-and-stick self-healing membrane tested to ANSI 118.12, flexible 112.5–225W/m² output and Warmup's SafetyNet guarantee.
From £14.95 inc. VAT
ThermoSphere
T-MO Smart Electric Heating Thermostat — White
Wi-Fi + Bluetooth smart thermostat with active energy metering, ZeroX relay protection, DirectLink multi-room control and a 5-year warranty. Works with any electric heating system up to 16A.
£149.00 inc. VAT
Warmup
7iE Smart Matter WiFi Thermostat — Bright Porcelain
The world's first floor heating thermostat with native Matter support. Control your floor through Apple Home, Google Home or Alexa with a stunning colour touchscreen and the MyHeating app.
£195.00 inc. VAT
Frequently asked questions
Can I use a Warmup 7iE thermostat with ThermoSphere underfloor heating?
Yes. The 7iE switches any direct electric heating load up to 16A, so it will happily control a ThermoSphere Ultimate cable system. Confirm the floor probe type at commissioning, and note that ThermoSphere's lifetime cable warranty terms reference installation with a compatible ThermoSphere thermostat and sensor, so check the warranty registration details for your project.
Can ThermoSphere Ultimate cable be laid into the Warmup DCM-PRO mat?
Yes. ThermoSphere states that the Ultimate cable is compatible with popular heating and decoupling membrane mats, including Warmup's DCM-PRO, so installers can use their preferred mat with the Ultimate cable.
Which system is better for a bathroom renovation?
Both excel in bathrooms: low build-up height, waterproof membranes and total layout freedom around sanitaryware. If you want the simplest possible joint handling and the strongest reliability guarantee, choose ThermoSphere Ultimate. If you need very specific output tuning or a low-wattage solution for a restricted supply, DCM-PRO offers the wider range.
Is electric underfloor heating expensive to run?
Running costs depend on room size, insulation, output and tariff. A typical 4m² bathroom system at 150W/m² running three hours a day costs pennies per day, and good insulation boards beneath the membrane can improve system efficiency dramatically. Smart thermostats with scheduling, energy metering and open-window detection keep consumption tightly controlled. See our electric underfloor heating FAQs for more detail.
Do I need an electrician to install these systems?
The membrane and cable laying can be done by a competent tiler or DIYer, but all final electrical connections, RCD protection and thermostat wiring must be completed and certified by a qualified electrician under UK wiring regulations. Resistance and insulation tests should be recorded before, during and after installation to validate the warranty.
Which floor finishes can go over a heated decoupling system?
Tile and stone are the natural fit and can be tiled directly over. Covered with a self-levelling compound, both systems also support engineered wood, vinyl, LVT and carpet certified for underfloor heating. See our guide to installing underfloor heating under wood, vinyl, carpet and LVT.
Need help sizing your underfloor heating project?
Our team supplies both ThermoSphere and Warmup systems across the UK with expert advice, trade pricing and express delivery. Send us your room dimensions and we'll spec the right cable, membrane and thermostat combination for you.
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