How to Install Hydronic Underfloor Heating: Step-by-Step Guide

There’s no getting away from it, underfloor heating installation is a large, complex job. After all, in a retrofit, the floor will have to be raised before work can proceed. However, it will all be worth it when you're enjoying a warm, energy-efficient home.

Once your hydronic underfloor heating system is installed, it can be integrated with a heat pump to produce renewable heating, capable of saving you hundreds on your energy bills. It will also guard your home against rising energy costs, future-proofing your home.

In this underfloor heating installation guide, we’ll take you through the installation process for hydronic (wet) systems. We'll also explain the components involved, from pipes to screed.

How are Hydronic Underfloor Heating Systems Installed?

Hydronic (wet) underfloor heating systems are more complicated to install than their dry counterparts, due to the plumbing work they require. As with electric systems, it’s much simpler to install hydronic systems in new self-build homes than it is to retrofit them. To cover all bases, this guide will take you through the process of a retrofit installation.

1. Preparing the room

Before the installation can begin, all furniture and obstructions need to be removed from the room. The flooring will then be carefully removed to prevent damaging to the subfloor. This is the layer that lies beneath the top layer of flooring for structural purposes. 

Once the flooring has been removed, the area will need to be thoroughly cleaned, with all dust and debris removed. 

2. Installing insulation

Without proper insulation, your underfloor heating system will lose a lot of heat and lack efficiency. Before any pipes are installed, a layer of insulation will be installed, preventing heat from escaping downwards when the system is up and running. Instead, the heat will rise, warming not only the floor, but the entire room. 

A vapour barrier will also be installed to prevent moisture damage. Moisture damage can ruin the structural integrity of your floor and cause mould to form. 

3. Installing the pipes

Once the floor has been fully insulated, the installer will begin to layout the pipes in accordance with the room layout. They will ensure an even spread to prevent cold spots from forming. The pipes are usually laid out in spiral or serpentine form, with the latter being a zig-zag pattern. 

The pipes will be placed approximately 10cm from the walls and tied down using clips or staples. Each pipe will be connected to a manifold, which controls the flow of water through the system.

4. Connecting to a heat source

When the pipes are in place and connected to the manifold, they will need to be attached to a heat source. This can either be a gas boiler, or an efficient, environmentally-friendly heat pump. This will be responsible for heating up the water running through the pipes. 

5. Screed application

A layer of screed will then be poured over the heating pipes. Screed is a mixture of sand, cement, and water, known for its high thermal conductivity. Its high thermal mass allows it to absorb heat and release it slowly, creating a stable, warm environment.

It’s the ideal component to transfer the heat from the pipes into the room, evenly warming the entire space. 

6. Laying the floor

Once the screed has dried, it will be time to relay the floor. The most important thing to consider at this point is whether your choice of flooring is compatible with the underfloor heating installation. Most options will be suitable, including carpets, tiles, and engineered flooring. However, high-tog carpets, non-certified vinyls, and solid hardwood should be avoided. 

The flooring should only be laid once the screed has fully dried and been smoothed out into a completely flat surface.

7. Testing the system

When the floor has been laid, the system should be allowed to run for a while before you start to use it properly. This will allow the screed and the floor to acclimatise to the heat. There will then be a final check, ensuring everything is working as it should be. You will then be given a tutorial on how to use the system, before it is finally handed over to you.