How to Install Underfloor Heating in Your En-Suite: Tips, Types & What to Expect

There is something to be said for stepping into a warm bathroom first thing in the morning on a cold day, particularly in a small, tiled en-suite, where comfort goes a long way. Underfloor heating is not only a luxurious addition; it’s also a pragmatic way to heat your space and conserve the precious wall space that radiators occupy.

If you’re considering installing underfloor heating in your en-suite (or are just keen to learn more about what it involves), this article covers it all: the various systems you can use, how it’s done, the best tips, and ways to avoid common mistakes. I’ve recently added underfloor heating to my own en-suite, so I’ll also provide practical tips and images throughout.

Why Choose Underfloor Heating for Your En-Suite?

En-suites are the obvious candidate for underfloor heating. The space is typically smaller, making installation easier and less expensive. Additionally, they heat up faster than in larger rooms. Whereas radiators require wall space, allowing them to influence how your space is laid out, underfloor systems are out of sight, leaving your room more open and clutter-free.

The best part is that when you wake up and climb out of bed first thing in the morning, nothing is better than feeling warm tiles against your toes!

Types of Underfloor Heating: Which One Is Right for You?

Electric (Dry) Systems

An electric underfloor heating system works by using heating cables or mats embedded under the floor surface. They’re homeowners’ first choice for en-suite renovations because they’re relatively easy to install, don’t add a lot of thickness to the floor, and don’t entail gutting and rerouting major plumbing lines.

• Ideal for small rooms and retrofits
• Fast to install
• Lower upfront cost, but higher running costs than wet systems

Water (Wet) Systems

These systems rely on hot water running through pipes located just below the floor. They are more energy-efficient in the long run, and, if you have one, the heat pump or modern boiler they work with for cooling or winter heating can be awesome. But installation is more complex.

• Best for new builds or major remodels
• Higher upfront cost
• Can be more economical over time

Foil Mats vs Loose Wire

In electric systems, you have foil heating mats, perfect for regular-shaped rooms, and loose wire systems, which allow you to work around curves and obstacles.

For my en-suite, I chose a foil mat electric system, which slotted in neatly around the existing fixtures and fittings in my bathroom, including the base of the shower and the basin.

Pre-Installation Checklist: What to Know Before You Start

Before you jump in, you’ll want to consider these crucial points:

• Insulation: You will need to lay insulating boards under the heating element to prevent heat from escaping downward. They also save you warm-up time.
• Flooring: Tile or stone works well with underfloor heat, thanks to their thermal conductivity. If you are using vinyl or laminate, ensure it is compatible.
• Subfloor condition: Is it level? Clean? Dry?
• Tools and materials: A multimeter, insulation board, heating mats or wire, adhesive, and a tile backer board will be necessary.
• Electrical work: Get a professional to do any mains wiring (such as for the thermostat).

Step-by-Step: How I Installed Underfloor Heating in My En-Suite

Here’s a quick overview of the steps I followed during my own dry underfloor heating installation:

1. Remove Existing Flooring

I tore out the old tile and glue to access the subfloor. The floor was smoothed so that there were no “bumps or dips” that might govern the heat in any direction, and this is critical for uniform heat distribution.

2. Lay Insulation Boards

On the floor, I laid 10mm insulation boards bedded in tile adhesive. Not only do these provide enhanced efficiency, but they also serve as a durable foundation for the heating mats.

3. Roll Out the Heating Mat

I dry-laid the mesh mat to measure up, ensuring it didn’t tuck under the toilet, shower or vanity unit. I cut through the mesh part, not the cord, to relocate the mat around obstructions.

4. Install Sensor & Connect to Thermostat

I centred the floor sensor between two runs of heating cable and routed all that back to the location of the thermostat. The wiring was professionally done. Don’t overlook this step.

5. Test Before Tiling

I measured resistance and continuity using a multimeter; do not skip this step! It guarantees that the system operates before it is buried forever.

6. Tile Over the Top

Once I was happy with everything, I applied a thin layer of self-levelling compound, then tiled on top using flexible tile adhesive. I removed the thermostat when everything was dry, and it was all set.

See the rest of my ensuite makeover here.

Top Tips for a Smooth Installation

After having gone through it myself, some of the key things to keep in mind to make your installation a success include:

• Measure twice, plan once: Plot out where the toilet, basin, and shower will go, and don’t put the heating underneath them.
• Use good insulation: It makes such a huge difference in performance and energy efficiency.
• Leave expansion gaps: Especially crucial when dealing with rigid flooring such as tile.
• Install the thermostat in an accessible, dry area: Mine is just outside the toilet door.
• Don’t overlap cables: Overlapping creates hot spots and will burn out the wire.

Find more tips and common mistakes with wetroom installations here.

Common Mistakes to Avoid

These are the errors I nearly made—and ones I’ve seen others make:

• Skipping the insulation layer: Heat just disappears downward into the subfloor.
• Laying heating under fixed units: Not only a waste of energy, but it can also cause overheating.
• Not testing the system before tiling: You don’t want to find out that something’s wrong after you’ve grouted.
• Choosing the wrong flooring: Some floor coverings can impede heat flow or be damaged by underfloor heating.

Final Thoughts: Is It Worth It?

Absolutely. It is an especially easy upgrade in a smaller room, such as an en-suite. Underfloor heating is relatively quick to install, and it adds both comfort and, if you decide to sell, resale value. It opens up wall space, simplifies the chore of cleaning the room, and will feel like a touch of luxury every morning.

Would I do it again? Yes! Actually, now I’m thinking about it for the main bathroom. Just make sure you carefully schedule, rely on good materials and don’t skip the testing phase.

Do you have questions about underfloor heating, or would you like to share your own installation story? Contact Next Level for assistance with underfloor heating in Edinburgh, Glasgow or further.