How to install underfloor heating

Underfloor heating is a great option as it provides effective heat to your home while running at a lower level than typical central heating systems. It can do this because it heats from the floor up instead of the ceiling down, unlike traditional radiators, meaning that it can create effective warmth much easier.

Which underfloor heating should I choose?

There are two main types of underfloor heating: electric and hydronic - more commonly referred to as wet and dry. Wet systems use pipes to run hot water from your boiler or heat pump whereas dry systems simply use electric heating elements.

As you can imagine, electric underfloor heating is far cheaper to install than wet underfloor heating. However, the running costs of wet underfloor heating are significantly lower which could offset that cost in the long term. You should also consider whether or not you’re willing to raise your floor during the renovation – this is often a requirement for wet systems while electric systems can keep the floor at its current height.

Wet underfloor systems run at a much lower temperature than radiators, meaning that they can be connected directly to a heat pump for eco-friendly heating which makes them perfect for eco-homes and sustainable living.

Before installing underfloor heating

Before you do anything towards installing your underfloor heating, you should first clean out your underfloor area to ensure that there is no debris or jagged edges that could damage your heating system. After this, you may have to put down a damp-proof membrane to protect your system.

Next, you will need to lay down insulation to make sure that you’re getting the most out of your heating. Insulation will stop heat from seeping into the foundations on your ground floor and make sure that the heat is reflected into the correct rooms on other floors.

Now you can begin marking out where you will want your underfloor heating to run. You should not install underfloor heating beneath cabinets or any permanent fittings, keeping around 15cm away from these areas. You will also want to keep a similar distance from skirting boards to avoid wasting heat. Choosing appropriate areas is important in any room, but it’s particularly key in bathrooms and kitchens that will have truly permanent fittings.

How to install wet underfloor heating

The first thing that you will have to site for wet underfloor heating is the manifold, as you will have to find an area that can support its weight and the weight of the attached piping. After this, you can start by laying down the pipe-fixing system you have and firmly attaching it to the floor.

After the fixing is firmly attached, you can start snaking the pipe across the designated area, pressing it into the fixing clips so that it’s secure. You will want to make sure that the distance between the pipes is around 200mm to 250mm, depending on your floor type. Most wet underfloor heating is designed to work with up to 100m of piping, so you should easily get an even distribution across the room.

Once you have set up your pipes, it’s time to pressure test. Bringing the system up to pressure will ensure that there are no leaks while you’re still in a position to fix them. You should leave the system at pressure and check the manifold, joints, and pipes for any drips. If everything looks good then it’s ready for screed application.

How to install electric underfloor heating

First, you will need to lay down the mat or loose cables in your marked area. You can easily make turns in matting by cutting the mesh – taking care not to cut the cable – then rotating the cut mat so that it runs in the opposite direction.

Before you glue this down, it’s a good idea to check that it’s working properly, using a multimeter to check that the current is flowing all the way through the cabling and that the electrical resistance is within the limits shown in the specifications.

After you’ve secured your mats (or loose cables) then you should secure the power supply cable - ideally by cutting it into the floor so that there’s no chance of it shifting. You will then have to secure the floor sensor between the mat turns where it can get a good reading of the floor temperature.

You should then get an electrician in to install the mains connection. Large areas especially shouldn’t be attempted without an electrician as load calculations will have to be made and very large installations may require a completely separate power supply.

If you don’t want to raise your floor level, you can choose not to install insulation below the mats and then use a flexible tile adhesive to tile directly on top of the wiring.

Screed

Screed is usually only used for wet underfloor heating and in electric underfloor heating that uses loose cables, as electric mats are glued down and flooring can be laid directly on top of them. It’s important when laying screed to ensure that your heating is turned off until it’s fully cured which can take up to seven days.

For wet systems, you should lay screed with the pressure turned on so that there is no risk of compressing the pipes. For both types of underfloor heating, you should make sure to include expansion joints so that the screed can expand and shrink due to the temperature changes without cracking.

The two main types of screed available are trowelling screed and liquid screed. Traditional semi-dry trowelling screed is much cheaper, but fast-flowing liquid screed can simply be poured over the system to the prescribed depth.

Top tips for installing underfloor heating

  • Make sure that there is no air in the pipes by flushing each loop individually, opening the valve that connects to the manifold.
  • Don’t attempt to plumb a wet system in yourself unless you are a competent plumber.
  • Check your wiring with a multimeter for current and resistance to catch faulty wiring early.
  • Don’t attempt to wire to mains yourself unless you are a competent electrician.
  • Plan out where your fittings will go well before you start so you don’t lay heating under these areas.