Considerations Required In The Processes Of Floor Screed Construction

Considerations Required Floor Screed Construction

Are you currently considering the floorscreeding requirements for your new home?

This can sometimes be a daunting task and it is important to understand the varying types of floor construction and materials that are available to you when deliberating over this important decision.

Firstly there are two types of ready mixed screed that will be available to you. These are as follows:

·  Sand and Cement Screed

·  Pumpable self smoothing screeds

There are several options available to you when using sand and cement screed. These are as follows:

·  Bonded Screed (Minimum thickness 25mm by British Standard BS8204-1:2003+A1:2009)

This construction consists of the levelling screeds being laid directly to the concrete substrate on a polymer bonding agent or grout.

·  Unbonded Screed (Minimum thickness 50mm by British Standard BS8204-1:2003+A1:2009)

This construction consists of the screed and the concrete being separated by a polythene layer/ DPM (Damp Proof Membrane)

·  Floating Screed/ Screed on Underfloor Heating (Minimum thickness 65mm by British Standard BS8204-1:2003+A1:2009)

The floating screed construction consists of the screed being separated by both a polythene layer and some form of insulation board or resilient layer. It is the case that many who build their own houses opt for an underfloor heating system which can be incorporated into the floating construction between the insulation and the screed.

When using Pumpable self smoothing screed the constructions that are available are unbonded and floating. However this type of screed can be laid thinner than sand and cement as follows:

·  Unbonded Construction – Minimum thickness 30mm

·  Floating Construction – Minimum thickness 35mm

·  Floating Construction incorporating Underfloor heating pipes – Minimum thickness 45mm (Minimum 25mm coverage over underfloor heating pipes)

All of the minimum thicknesses above are based on British Standard BS8204-7:2003

A floor screed is the perfect solution to provide a level base to lay a variety of floor finishes and sand and cement screed can be stepped where different floor finishes meet. For example if you have a 10mm tile in the kitchen but a 20mm wooden floor in the lounge the screed can be laid 10mm lower in the lounge so that the floor finishes run flush at the door threshold where they meet.

There are several pros and cons in the debate sand and cement versus pumpable self smoothing screed some of which are detailed below.

Sand/cement screed

Pros

  • Cheaper in smaller areas
  • More readily available countrywide
  • Able to lay at differing levels
  • Laid to falls in wet areas/bathrooms
  • Dry’s quicker due to much lower water content
  • Suitable for use with liquid DPMs
  • Compatible with all cement adhesives
  • Can be laid before the building is completely weather tight

Cons

  • Small amount of cracking/ shrinkage to be expected
  • Force drying not recommended

Liquid screed

Pros

  • Screed pipes are encapsulated
  • Up to 1000m2 poured in one day
  • Very little cracking if any
  • Can be force dried

Cons

  • Extensive drying times
  • Building needs to be fully weather tight before screed is laid
  • Fully sealed floor preparation
  • Not directly compatible with cement based adhesives
  • Liquid DPM are not compatible
  • Screed needs to be fully dry before floor coverings are applied
  • Delays in material deliveries can result in problematic cold joint

We are specialist screed installers and specialize in Floor Screed Construction