Installation of Screedflo screed

Screedflo can be installed very easily, but it is only as good as the floor preparation beneath it.

Insulation:

Usually the screed will be installed on top of some form of insulation. This is often Celotex, Kingspan or expanded polystyrene. These come in boards which must be laid so that they are stable when walked on. Where there are service pipes running across the floor, such as gas pipes, the insulation should be grooved on the underside to allow the pipes to sit within the insulation, rather than leaving the boards resting on top of the pipes.

Edge strip

Once the insulation is installed, any vertical surface that is going to have screed running up to it, such as walls, stairs or pipes, should have a foam insulation edge strip stuck to it. This is to allow for any minor expansion once the screed is dry. There are various types of strip, but they are typically 8mm-10mm thick and come in rolls.

Tanking membrane

The tanking membrane consists of a reasonably heavy gauge polythene which is placed on top of the insulation. The tanking membrane is not there to act as a damp proof membrane, but rather to stop the screed from escaping when it is poured. Care should be taken to make sure that all the joints are overlapped by at least 100mm and fully taped. Additionally, the polythene should be taken at least to the height of the edge strip up the face of any walls, pipes etc. and taped fully along the top edge.

Underfloor heating

The pipes or cables for underfloor heating should always be installed on top of the tanking membrane, not beneath it. The screws or staples used to hold the pipe or cable down will pierce the polythene, but seal the holes themselves, and do not cause any leaks.

Regardless of which system is used to hold down the cables or pipes, it should be installed so that there are no unfixed lengths of pipe or cable greater than 300mm long. If left unfixed, all underfloor heating elements will float to the surface of the screed, even if filled with water.

Once all of this is installed correctly, it is time to do the screeding.

Setting the levels

We will work from a place called a datum point. Typically, this will be from the stairs, but can also be from other areas such as a doorway or threshold.

We will then set out levelling gauges called 'tripods' and, using a laser, will set them to the correct depth to make sure that the finished screed surface is level throughout the building.

Screeding

The screed will then be pumped in and poured to the depths given by the tripods. To make sure that it is smooth, without any tide marks or air bubbles, we will then agitate it using a dappling bar throughout the screed. Once this is done the tripods are removed, and the screeding is finished.

Drying the screed

The screed should now be left untouched until it is solid, which usually takes 48 hours. During this time, all the windows and doors should be kept shut and nobody should walk on the screed. Once the screed has become solid, the windows should then be opened to allow evaporation to take place helping the final drying stages. For more information on drying, see our Screedflo Maintenance Sheet.