Installing Underfloor Heating: What to Know, What to Watch Out For & How to Keep Costs Down

Underfloor heating has become increasingly popular, providing a way for homeowners to enjoy warm rooms while reducing their heating bills. It’s low-profile, eliminates the need for bulky radiators, and offers uniform heat across the entire floor area.

No surprise, then, that it’s ideally suited for those everything-but-the-kitchen-sink renovations, from open-plan kitchens to bathroom overhauls.

However, as enticing as those advantages are, installing underfloor heating, especially under floors that aren’t perfectly level or in new extensions, does require some careful preplanning.

In this guide, we’ll take you through the installation process, essential considerations (including what to do when you have challenging floor conditions), and cost-effective alternatives to repeating the process.

Step-by-Step: How Underfloor Heating Is Installed

Whether you’re simply looking to lay UFH in one room of your house or are installing it as part of a wider extension, there are several critical stages to the installation:

1. Assess the Subfloor

First, the obvious is that the subfloor needs to be addressed. A floor that has been laid unevenly can disturb the heat distribution settings or damage the system. Cracks and pin holes can be filled with a self-levelling compound, and deeper depressions will require a full flow or a levelling screed.

2. Choose the Right System

There are two main types of underfloor heating:

• Dry electric systems are more affordable but less effective than hydronic floor heating. They are best suited for smaller spaces, retrofit projects, or where a hydronic system is not feasible.

• Wet systems (hydronic) deliver hot water through pipes and are more energy-efficient when heating larger spaces or an entire home. They work well in new builds and extensions.

3. Install Insulation

Proper insulation is essential for producing optimal and cost-effective system performance. Insulation boards and insulating reflective foil prevent downward heat loss, forcing it to pass upwards into the room rather than into the floor.

4. Lay Heating Elements

Regardless of whether it is electric mats, loose wires, water pipes, or other elements, they are carefully laid out according to the plan. Spacing shall be consistent, and overlapping shall be avoided. Water pipes are securely clipped in place, and the water system is tested for leaks.

5. Connect to Controls

After systems are in place, they are linked to a thermostat or a smart heating control. Wired electric and connected to the mains, wet systems run from the central boiler or heat pump. Another possibility is zoning, which is likely to result in even more targeted room-by-room control (and even greater energy savings).

6. Cover and Finish

Electric systems are typically encapsulated in a flexible tile adhesive, backer board, or dry screed. By comparison, wet systems typically have the entire screed poured over the pipes to shield them and provide thermal mass. And as soon as it is all dry, you can apply the chosen floor treatment.

Key Considerations – Especially in Extensions or Older Properties

In new builds, the installation can be straightforward, but in older houses and property extensions, challenges can arise. Here's what to consider:

Uneven Floors

The floors are one of the most significant challenges. Lack of levelling leaves potential for air pockets or areas with hotter or colder temperatures, negatively affecting the system’s efficiency.

• Minor unevenness? A premix self-levelling compound is usually adequate.

• Major level differences? It may require a full floor screed or a levelling board system.

• With some electric systems, it is also possible to lay them over decoupling membranes, which are designed to bridge minor irregularities in the ground.

Floor Build-Up Height

With underfloor heating, the increased floor depth can be an issue with existing door thresholds, skirting, and transitions to other rooms.

• Wet systems typically add 50–100mm.

• Slimline or low-profile systems can reduce this to around 15–20mm.

This is especially important if you’re working in a room with tight headroom (such as a basement or loft conversion).

Thermal Performance of Extensions

An extension will generally be better insulated than the rest of the property. This can be a challenge in getting both spaces to heat evenly.

The solution? Install independent heating zones and thermostats. This allows you to regulate temperatures accordingly, increasing comfort while also conserving energy.

Insulation in Older Properties

Many older homes have insufficient insulation, which will compromise the performance of underfloor heating. Before installation, confirm the appropriate floor insulation thickness and upgrade if necessary. Even solid floors can be improved with insulation boards or insulating membranes.

Common Challenges and How to Overcome Them (Affordably)

Underfloor heating doesn’t have to cost a fortune. If you plan smartly, you can effectively control costs and avoid the typical pitfalls.

Challenge 1: Uneven Floors and a Limited Budget

Levelling can become costly if you aren’t optimising the approach.

• For minor issues, a self-levelling compound provides a quick and inexpensive remedy.

• For even greater unevennesses, modular overlay boards are a more economical alternative to screed, particularly with electric systems.

• If money is tight, you could put underfloor heating only in high-traffic rooms or key living areas, and add more heat sources elsewhere.

Challenge 2: Minimising Disruption

Underfloor heating installation can be disruptive if not timed right.

• Pair it with another big-ticket task, such as laying new floors, rewiring, or plumbing, to save on labour and minimise any inconveniences.

• For extensions, fit the overall system before internal walls are erected for complete coverage and easy pipework routing.

Challenge 3: Keeping Running Costs Down

Resist the temptation to skimp on insulation. Strong insulation can lower operating expenses by up to 50%.

Also consider:

• Fitting smart thermostats, boosters, or time and temperature controls for more accurate temperature heating.

• Utilising good quality materials and reputable installers, so you don’t have to spend money down the road fixing it.

Challenge 4: Flooring Compatibility

Underfloor heating is not compatible with all types of flooring.

• Best options: engineered wood, tiles, vinyl, and laminate.

• Avoid: solid hardwood (which can warp with heat) and thick carpets (that insulate too well and reduce heat output).

• Reusing flooring? Check the manufacturer's guidelines for temperature limits and compatibility with underfloor heating.

Final Thoughts: Is Underfloor Heating Right for Your Project?

Underfloor heating can be a game changer when it comes to comfort and energy efficiency, but, like so many other home improvements, it pays to be informed and take the time to do it right.

It’s the perfect time to consider it if you're already renovating, adding on, or replacing floors. Although the uneven floor, build-up height and insulating issues do present problems, there are low-budget solutions for each, so don’t be put off.

Bring the experts at Next Level in to help you select the correct system for your needs, level up smartly, and insulate your Edinburgh, Glasgow or home in any area of Scotland correctly.

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Our writers like to blog about interiors. We launched the award-winning Seasons in Colour in 2015 and the luxury property and interior decor blog www.alltheprettyhomes.com in 2024 to cover all your interior design, travel and lifestyle inspiration needs. Download our free bathroom renovation guide here.