Types Of Screed

What is a screed?

Screed is a layer of cement mixed with sand over a concrete substrate, onto which various types of flooring can be laid. Screed provides long-term solidity in your floors and is widely used in commercial, domestic and outdoor use. There are 3 different types of screed: bonded, unbonded & floating.

Bonded Screed

This type of screed is bonded by slurrying bonding to the concrete substrate. This is the ideal type of screed for thinner applications where heavy loading is anticipated.

Unbonded Screed

As the name suggests, unbonded screeds are not bonded directly to the base, but applied to polythene/damp proof membrane (DPM) laid on top of the concrete base. This is ideal for thickness greater than 50mm for standard screed. Some modified screeds can be installed at thinner applications, it would be advised to refer to the data sheet of a screed to determine the minimum thickness of an unbonded screed.

Floating Screed

With the drive to gain an A1 rating in modern dwelling, the use of insulation in a floor build-up is becoming the normal practice. With this a floating screed has become a popular option. A floating screed is generally laid on a layer of insulation with a slip membrane over it separating the insulation from the screed. The build-up is generally a slip membrane (sheet of polythene) 150mm+insulation another slip membrane, then 65mm of screed for domestic dwellings (75mm for commercial locations).

Another popular type is a floating screed with underfloor heating, which is bascially a screed laid over an underfloor heating system. Always ensure the system is working before the screed is laid over it, this can avoid costly repairs.