Sand Cement Screed Thickness Minimum?

I’m Andy Parkin. Managing Director of the Multi Award Winning Speed Screed. I’m here today to talk about Sand and Cement Screed thickness and what the minimum depth is.

When we talk about how thin a screed can go, we need to look at the different types of construction that you may come across. So you can put that into context of what, perhaps, your project may be.

There are three types of construction.

Bonded

The screed is bonded directly onto the substrate, which is normally a structural concrete.

Unbonded

This allows for a membrane (a separating membrane), even a damp proof membrane between the substrate and the screed.

Floating

The screed is laid onto thermal or acoustic installation, there could also be a membrane on the insulation.

There are three main types of construction, and each one allows for a different minimum thickness for sand and cement screed.

Bonded Sand and Cement Screed Minimum Thickness

When we say modified it has add mixtures that allow it to perform differently from a traditional sand and cement screed. Now that could be plasticisers, or hydraulic binders. 10mm would general be the minimum of any sand and cement screed, and would require bonding.  A bonding agent is used to bond the screed to the substrate. You need to take particular care when bonding to the substrate, make sure that it’s clean, dust free, free from contaminants and that it is actually sound.

There may need to be preparation carried out on certain existing concrete floors, and certainly for a new concrete floor the laitance will probably need to be removed and the 1 or 2mm of the concrete matrix might need to be removed.  The removal leaves a surface the bonding agent can bond to, ensuring the screed does it’s job.

  • 40mm traditional sand and cement screed.

A traditional sand and cement screed is normally a 1:4 or a 1:3. The minimum sand and cement screed thickness would be 40mm as defined by the British standard.

Unbonded Sand and Cement Screed Minimum Thickness

Laying onto a substrate with a separating membrane on the minimums are as follows:

  • 35mm modified sand and cement, this is a rapid setting product
  • 50mm traditional sand and cement screed, as defined by the British Standard

Floating Sand and Cement Screed Minimum Thickness

Laying onto insulation the minimum depths are as follows:

I hope that helps and gives you an idea of sand and cement screed minimum thickness.

If you’ve any further questions just please let me know. I’d be happy to answer any further questions that you may have.

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