Floor Screeding Guide

The Basics of Floor Screeding

Why apply screed to a floor?

Floor screeding is used in most development projects. The purpose of it is to create a more level finish so that the final floor finishes such as tiles, carpet or wooden flooring can be applied. This is because the concrete slab that the screed is applied to is usually uneven and bumpy due to the larger aggregate used. The sand in screed uses much finer aggregate which allows for a much smoother surface.

How is floor screeding applied?

The four main ways it is applied are:

  • Bonded – The screed layer is fully bonded to the substrate using a bonding agent or a primer. It is most commonly used in areas that will experience heavy loading.
  • Unbonded – The screed layer is not bonded to the base, but instead it is applied to a Damp-Proof Membrane (DPM) or polythene sheet, separating the screed from the concrete.
  • Floating – Floating screed is most commonly used in residential properties as the screed is applied on top of a layer of thermal/acoustic insulation. The insulation is usually applied on to the DPM.
  • Modified – This is essentially the same as the other forms of application however, the screed is applied over an underfloor heating system

What are the different types of screed?

We will be looking at the three main types of floor screed which are:

The specifics of each different type of screed is going to be discussed in more depth in their individual guides.

Drying Times and Reinforcement

One of the main questions asked when seeking advice on screeding is the time it takes to dry. This will vary depending on whether additives have been applied to the screed or not. Without any additives, screed can take up to 30 days to dry if not longer. With additives, light foot traffic is possible after 24 hours. However these numbers will also vary depending on the type of screed you use and the additives used. In each individual guide, we will go through the different drying times and additives that can be used.

Reinforcement is used in areas of heavy loads. For example, a metal mesh called D49 can be applied on the floor before the screed is applied on top to give the screed that extra strength. However, fibre screed also reinforces the screed and is more often used than mesh reinforcement.

Floor Preparation and Insulation

Before any screed is applied, the floor must be well prepared to maintain the quality of its screed throughout its lifetime. The process of the floor preparation will vary depending on the type of screed used and the way it is applied.

Insulation is also commonly used on many development projects but depends on the way it is applied. For example, bonded screed is bonded directly to the concrete slab without the need for insulation whereas floating screed is applied on top of the insulation.

More details will be discussed in the individual guides so that you will get more of an understanding of how each type of screed and different methods of application can vary.

Screed Testing and Protection

Screed testing is essential to guarantee that the strength of the screed matches the specification that the client has requested. This is because screed varies in strength depending on the type of screed used, the additives and different types of reinforcements used within the screed. Therefore, the screed has to match the strength for it’s required purpose.

Once the screed is applied, protection is vital. If the screed is exposed to unfavourable conditions of the environment, the screed can crack and be damaged.