Installing underfloor heating is becoming increasingly popular, especially installing the wet type of flooring kit in new builds or renovation projects. This doesn’t mean it cannot be installed in existing properties, however, as you will see from our handy how to install wet underfloor heating guide.
Important note – this is a general how to guide so that you have a better idea of what is involved in the installation process. If you are unsure about any aspect of the installation or design process, we suggest you contact us for further advice and guidance. Installing the system incorrectly can mean it malfunctions or fails to perform at all, leading to possible damage of the system and your floor.
Is there an existing floor?
Wet underfloor heating systems heat the floor by pumping hot water through a series of pipes, laid out in looped rows under the top layer of floor and encased in screed, a thin layer of concrete.
This means that they need a certain amount of room to be ‘sunk’ into the floor and even though there are now wet underfloor systems that are thinner, if you do not dig out the sub-floor, this system will add height to your current floor level. This means taking off internal doors and cutting off a slice from the bottom of it, rehanging it etc.
This does make wet underfloor heating impossible to lay in existing properties. With a little extra effort, you can have this type of underfloor heating fitted giving you brilliant, cost-effective running costs.
The following steps should now be followed once you have your sub-floor prepared…
- Clean the sub floor well, ensuring that no debris is left behind. Add a damp proof membrane – sometimes known as DPM – is necessary. If there are any bits of the wall that stick out or are sharp, these need to be cut away or filed.
- Next lay the floor insulation as neatly as possible. We know that heat is lost through the roof, walls and windows but in the case of underfloor heating, you need as much of the heat from the pipes to rise upwards with a minimal amount lost under the floor, hence the need for insulation. Make sure the seams are taped.
- Fix the piping fix system to the insulation at a 90° angle to the direction the pipes are to be laid. These are small grab arms, into which the pipe is slotted.
- BEFORE you lay any piping, you need to mount the manifold on a wall in a suitable location. You need to be confident that the wall is strong enough to support the weight of both the manifold itself and connecting pipe work. You will need to work from the manifold with each pipe loop and connect each returning pipe, and not vice versa. This is an integral part of how to install wet underfloor heating correctly whilst also ensuring it works correctly.
- Ensure that the heating pipe is fitted in to the flow side of the manifold – this will be arrowed – once you have reamed the end of it with the tool normally provided in underfloor heating kits. This ensures the sealing O-rings are not damaged.
- The pipe can now be snaked out from the manifold across the floor to the furthest part of the room and back again. Allow around 200mm of spacing between each run of piping. Larger rooms can have two or even three loops. Make sure each loop is laid in equal lengths. Make sure each section of the pipe is fully clipped in.
- Once you have laid the piping, you can now pressure test the system. By doing so at this point before you lay the screed, you can check for leaks in pipes, joints and at the manifold.
- Keeping the system under pressure, lay the screed and whilst the screed is drying, make sure that the pressure is still on in the piping. If not, when you operate your heating system, the cement mix will be too tight around the pipework, constricting it.
- Using a competent plumber, connect the manifold to the boiler pump and ensure the system is working fully.
- Use the services of a qualified electrician to fix the thermostat to the underfloor heating system.
We always suggest leaving the heat off in the system until the screed has been allowed to cure or set completely but still maintain the pressure in the system. By switching the system on too early, it could lead to damage to the screed layer which can cause problems in the longer term.
When you are ready to switch the system on, start running it at a much lower temperature and build up, little by little every day. Most underfloor heating kits will come with full advice and installation guidance, including start up and final temperatures.
All that remains is to choose and install your top layer of flooring!
