Table of Contents
Traditional bonded sand cement screeds, generally should not be installed to a thickness less than 15mm. Engineered screeds from the ScreedMax Pro range including the Mapei Topcem screed can be installed to a minimum of10mm.
What is the minimum thickness of floor screed?
The minimum thickness of an unbonded traditional screed will usually be around 50mm. An unbonded Cemfloor Screed would usually require a minimum of 30mm thickness. Floating screed: This is where the screed is overlaid on something that is compressible and not rigid.
How thin can screed be laid?
Calcium sulphate flow screed can be laid at 35 mm, for domestic, and 40 mm for commercial projects. Sand and cement modified screed for rapid strength starts at 35 mm. Traditional sand and cement screed is 65 mm for domestic and 75 mm for commercial.
How thin can Levelling compound be?
The minimum thickness advised for many levelling compounds is only 2 or 3 millimetres (some require a minimum of 5mm). And whilst even a millimetre less than the prescribed minimum might not seem that significant, it can cause problems.
What is the thinnest sand and cement screed?
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.
What depth should floor screed be?
The optimum thickness of a sand and cement bonded screed is 25–40mm, an unbonded screed should have a minimum thickness of 50mm, whilst a floating screed should have a thickness greater than 65mm for lightly loaded floors and 75mm for more heavily loaded floors.
How thick should shower screed be?
A minimum thickness of 10mm is recommended when using diluted ARDEX Abacrete instead of water; 15mm when mixed with water. For a thickness greater than 40mm, reinforcing mesh is required.
What happens if screed is too thin?
Traditional cement sand screeds An unbonded screed is separated from the slab or substrate below, and the main way that an unbonded screed fails is to lift or curl. This is more likely to happen if the screed is too thin. Bonded screeds should therefore be thin, normally less than 50mm.
Can I screed over old screed?
Yes you can. The main reason to use concrete screed is to pour over a pre existing concrete floor / slab / sub base to level it out and leave a smooth finish.
What is the minimum cement thickness?
The minimum recommended thickness is 1 to 2 in. (25 to 50 mm) for a fully bonded concrete overlay placed on a base slab that is practically free of cracks and in which the concrete is sound, clean, and of good quality.
What is the thinnest self Levelling compound?
Sikafloor is an acrylic self-leveling compound that comes in both standard and Latex variations for an extra supple surface. It can be laid thinner than the other options on this list, spreading as thin as 1/25 inch, or as thick as 1 ½ inch.
Do I need to prime self Levelling compound before tiling?
Subfloors should always be primed. The substrate must be clean, dry and free from dust, laitance and any other contaminants which may act as a release agent, preventing the leveller from bonding to the surface.
Does self-leveling concrete crack?
A DIY self-levelling cement job might look good for a few months, maybe even a couple years. But if it’s not done properly, eventually it can start to crack. If your floors move or bounce, that cement can crack, too.
How do you bond screed to concrete?
Fully bonded screeds need to be laid on a shot-blasted / scabbled concrete base, and be bonded using an adhesive such as PVA, SBR, epoxy resin or good old fashioned cement. PVA glue is a good screed adhesive especially if it is mixed with water & cement, to make a slurry.
Why is a floor screed a dry mix?
Dry screed consists of aggregates (such as sand) and cement, with a ratio of between 3-5 parts aggregate and 1 part cement. This creates a thin, concrete-like substance that will clump together when squeezed.
Can I use concrete instead of screed?
Because concrete has the potential to hit very high strengths, it is used across the construction industry for structural purposes – including floor slabs. Screed however is a smoother mix, which consists of considerably less aggregates to that of the mix used for concrete.
What is the minimum screed depth?
The minimum screed thickness you should use for warm water underfloor heating systems is: Minimum depth of 65mm for hand-mixed screed. Minimum depth of 50mm for liquid screed.
Why does screed crack?
Cracks typically form in new screeds because the excess water evaporates from the surface at a faster pace than it is replaced by the residual water, trapped in the concrete slab. This can be caused by not enough or too much water added during the mixing process or simply poor mixing.
How thick can you lay liquid screed?
Unbonded liquid screed thickness minimum would be 15mm for the specialist version and 30mm for standard. Unbonded liquid screed thickness maximum would be 80mm for the specialist version and 80mm for standard.
Can you tile directly onto screed?
It’s quite common in modern construction and has many benefits over sand and cement screeds, but you can’t tile straight onto it with standard adhesives. If you do, there will be a chemical reaction between the screed and the adhesive, and the adhesive will eventually separate from the screed.
Is screed as strong as concrete?
The aggregates used for making concrete are hard-core and have a coarse structure while screed is free from any aggregates. This is why concrete is stronger and is longer-lasting than screed which is smoother.
Do you waterproof or screed first?
AS 3740-2010 3.2 states: Where a tile bed or screed is used, the waterproof membrane shall be installed above or below the tile bed or screed.
