If you are considering installing underfloor heating in your home there are benefits to be had, but also one or two issues to deal with. If it is a new build, then the main problem can be taken into account at the design stage, but if you are retro-fitting underfloor heating you need to consider it.

This is that, when fitting underfloor heating you will generally lose some height in the room. Not only do you have the space taken up by the underfloor heating itself, but you also have to allow for a screed to be installed in order to cover the underfloor heating system, and in an ideal world you will also want to install thermal insulation.

In a new build property, you would start with the substrate and make sure that it is swept clean, and then the next thing that you want to do is to install insulation boards. If there are any service pipes such as gas pipes running across the floor, then you would need to cut a groove in the bottom of the insulation boards in order to ensure that the boards lay flat on the floor and don’t interfere with the pipes. The first layer of boards goes flat on the floor.

Another way of doing this is to lay the insulation boards so that the service pipes run between them and up as close to them as possible and then fill any voids with dried sand and level it off. Then you place a second layer of insulation boards on top of the first, and ideally at right angles to the first layer, and make certain that they also lie flat. The purpose of the insulation boards is to prevent the heat going downwards and thus wasting energy. You want it all to go up into the room.

On top of the insulation boards, you need to lay a sheet of 500-gauge plastic membrane and ensure that it is pulled tight without any creases, and also ensure that joints overlap by at least 100mm. At the walls the membrane also needs to run up the walls by 100mm so that a perimeter edging strip can be placed on top. This needs to be stapled into place using a staple gun. The purpose of the membrane is to ensure that all of the liquid screed is prevented from running away when it is poured.

Now The Heating Pipes Need To Be Installed

The next job is to install the underfloor heating pipes, and these need to be screwed or stapled down at distance of no more than 300mm, and less on the bends. The screws or staples will pierce the polythene but seal the holes themselves so there will be no leaks. The heating pipes need to be securely fixed because if not they will float upwards when the screed is poured. In addition, you need to fill the water pipes before the screed is installed to give added weight to them.

Of course, at UK Screeds, we will do all of this for you when we install your underfloor heating if you are using our underfloor heating and liquid screed services in Bristol – or anywhere else in England and Wales.

The minimum thickness of the screed for covering the heating pipes is 30mm above them, making a total screed thickness of 45mm to 50mm. You can readily see why this will reduce the height of a room in an existing property, but of course in a new build it can all be taken into account at the design stage. 

When we are ready to pour the screed – which is delivered to site ready mixed – we use levelling gauges called tripods and these are set out to the correct depth using a laser. This ensures that when the screed is poured it will cover the heating pipes to the required depth and be level throughout the building.

We then pump the screed into position using a pump and hose and then remove the tripods. The final task is to agitate the screed using a dappling bar in order to remove any air bubbles.

Once this has been done, the screed can be left to dry. The drying time is up to 48 hours, after which the screed is hard enough to walk on.