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Solid Floor Constructions

Screeded Floors - Expansion

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All cement based materials shrink as they dry, these materials also expand and contract with the temperature, these characteristics are also exaggerated by Underfloor heating systems.

This drying, shrinkage and thermal movement causes the screed to crack and therefore due to this shrinkage and movement screeds are generally specified with movement joints at set positions.

The type of finished flooring will affect the positioning of the joints in the screed and may also affect the positioning of the underfloor heating pipes. Guidance for installation & spacing of joints in screed is specified in BS-8204-2.

Expansion joints should be included in the floor if the final floor finish is to be a ceramic tile or similar. These will be required if the floor area is greater than 40m² and then the floor area should be divided into bays with 8m being the maximum length as shown above.

Other types of joints may be present within the floor structure required as part of the structural design of the floor such as day joints. In these cases the Underfloor heating pipework should be sleeved where it passes through a joint system or over a joint line.

With Screeded floors, crack inducers may be included in the top surface of the screed these are generally a 5mm mechanical saw cut in the top surface of the screed. In this case the Underfloor heating pipework should be sleeved where it passes below the crack inducement line.

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