What is a green screed?

BAL Green Screed Adhesive is a polymer-modified, cement-based, flexible tile adhesive for newly laid floors. It is designed specifically for fast-track tiling on recently laid screeds/concrete and on low porosity substrates.

Can I tile straight 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.

What's the difference between concrete and screed?

Concrete is a mixture of cement, water, aggregates and sometimes admixtures. It is typically used for structural purposes such as foundations, floors, walls and beams. Screed, on the other hand, is a thinner mixture of cement and aggregates, without any water.

Do I need to screed before tiling?

When laying tiles or laminated or vinyl flooring it is necessary to use a screed if the structural floor is not level. As a general rule the floor surface should not vary by more than 5mm per 3 metres.

Is screed better than concrete?

Concrete is known for its impressive strength and durability, and this is largely due to the incorporation of coarse aggregates into its mix. Screed is mixed with much finer aggregates than concrete, giving it a far smoother quality.

How to Tile onto a Green Screed Using Norcros Permalayer Anti-Fracture Matting

Can I screed over concrete?

Screed is usually applied on top of the concrete slab and is most commonly used as a finishing layer on internal floors or to level the floor prior to final floor coverings carpet, tiles, natural stone, linoleum, wood flooring, resin coatings etc.

How thick can screed be?

The screed thickness should not be less than 50mm; therefore, to allow for deviations in the finished levels, the specified design thickness should be a minimum of 70mm. However, BS 8204-1 emphasizes that there is a high risk of screed curling with unbonded and floating levelling screeds.

How soon can you tile after screeding?

Screeds should be firm enough to walk on, usually at least 3 days after application, before tiling can be started. Concrete should be at least 7 days old. All substrates to be tiled must be clean and surface dry.

Can you lay porcelain tiles on screed?

Porcelain slabs are suitable for fixing on screed both for internal and external projects. If you are laying screed on top of an existing smooth or shiny floor, you may need to key the surface to ensure stability.

Is screed the same as self Levelling?

Firstly, calling something 'self levelling' can be a little misleading because the screed will not level itself. In reality, the screed should be called self-smoothing. However, it is more commonly known as self-levelling within the industry.

Can you use sand and cement as screed?

Floor screed is commonly made by mixing cement with sharp sand. The most common ratio used for sand and cement screed is 1:3 or 1:4.5 which gives the most suitable consistency for adding to a concrete floor unit or slab.

Does screed set hard?

For areas which receive heavier foot traffic or if you're hoping to move or place heavy furniture on it, we recommend leaving it for around 5-7 days. Typically, most screeds will reach full cured strength after approximately 28 days.

Why do floor screeds 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. Or at stress points such as doorways and corners.

Why is my screed crumbling?

Crumbling is caused by a lack of compaction or low cement content. A screed tester (in accordance with BS 8204) is likely to show that the screed falls short of the lowest Category C (indentation of 5 mm). An analysis to assess the proportion of sand to cement might indicate a low cement content.

Why does screed fail?

The screed will only be as good as the substrate that it is laid on. If the substrate is not sound, dry, contaminated, stable, insulation is rocking or you have gapping, there will be issues with the screed. Preparation is always key when working with screed. Has there been too much water, too little water?

Can I use PVA to seal a screed floor?

There are several reasons you should know how to seal concrete floor with PVA – to keep down the dust, provide a waterproof seal, and give a bond for a finishing layer of paint, tile, or screed.

Do I need to waterproof concrete floor before tiling?

Sealing a concrete floor before covering it with tile or carpet is a great idea. Sealing the concrete can prevent condensation and protect the floor. This means your carpet or tile stays dry and thus lowers the chances of mold and mildew building up.

How long does 75mm screed take to dry?

According to industry guidelines a 75mm traditional screed would require up to 110 days to dry at 20˚C and 50%RH at the rate of 1mm per day for the first 40mm and 0.5 mm thereafter.

What is the minimum thickness for 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 much screed can be laid in a day?

A good screed gang of two people can lay up to 150 square metres per day.

Do you waterproof over or under screed?

Do we waterproof above or below the screed? 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. Both are correct, and have their various uses.

What is the thickest you can lay screed?

What is the maximum screed thickness? Generally smoothing compounds, are designed to be used up to 10mm. Certain smoothing compounds maximum is up to 50mm. The range of those products would be something like 5-50mm.

How deep can you go with screed?

Bonded Screed Maximum Depth

Modified sand and cement screeds can go up to whatever thickness you would like, however you would question doing so, if you are starting to get up to 150mm, 200mm. At those kind of depths, you would using void formers (insulation and then screed on top).

What is the best mix for floor screed?

What is the Right Mix for Floor Screed? The right mix for a sand and cement floor screed is a strong mix of 3:1 or 4:1 sharp sand and cement. The mix should also be fairly dry and sharp sand should be used.