What is an anhydrite screed?

Anhydrite screeds are a mixture of screeding sand and binder. If tilers are unsure of whether the screed they're to work on is, or isn't, anhydrite, they should always ask. Information about the screed should be kept in the building owner's Operation and Maintenance Manual. Movement Joints.

What does anhydrite screed look like?

Anhydrite screeds may be difficult to identify

Consequently they can look very similar to a sand/cement screed. Anhydrite will tend to appear lighter, sometimes almost white, but in practice it is difficult to identify an existing anhydrite screed from a traditional one.

Is liquid screed anhydrite?

Anhydrite Liquid Screed is a screeding product that is often chosen over traditional sand and cement screed due to its many advantages. Up to 1500m2 of Anhydrite screed can be installed within one day; and since the Liquid Screed cures quickly, there is enough strength to allow foot traffic after 24-48 hours.

How long does it take for anhydrite screed to dry?

This means that a typical anhydrite screed dries in about 49 days – compared to around 21 days for Ordinary Portland Cement.

Can you polish anhydrite screed?

YOU CAN POLISH A FLOOR SCREED BY USING OUR PRODUCTS

Flooring contractors are happy to work with us as laying a screed slab with a smooth surface is always easier than laying a concrete ready for polishing.

How to identify an anhydrite screed prior to tiling

How do you remove Laitance from anhydrite screed?

Laitance should be removed by light abrasion using a suitable sanding machine i.e. a rotary floor scarifier and a 60's grit sandpaper. Remove excess dust completely with a vacuum cleaner. Abrading the surface is best carried out 4-6 days after the application of the screed and can assist in the drying out process.

Can screed be used as a floor finish?

It's not unusual for screed to be laid as the finish – it can look very smart and provide a functional floor, especially in commercial locations. It can also be used as a base for final floor finishes such as resin flooring. Screed's properties also make it ideal as an insulation material for underfloor heating pipes.

How long after screed can you turn on underfloor heating?

Hand mixed screed for underfloor heating

In practice, 4 weeks is a sensible minimum drying time to leave hand mixed underfloor heating screeds.

Can I screed over 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.

How soon can you self level over new screed?

Provided your screed is layed correctly there is no need for self levelling. You will need to allow 5 - 6 weeks drying time beore tiling, or use 'Bal Greenscreed' adhesive, in which case you can tile after a couple of weeks. Best of luck.

Do I need to screed a concrete floor?

Screeds are required when a colourful or functional floor is needed rather than a bare concrete surface. For industrial purposes, or commercial locations, which will undergo frequent traffic, a more robust screed is required than is used in DIY or residential projects.

Can you tile straight onto liquid screed?

This layer is too weak to tile onto and can also inhibit the screed from drying. Before laying tiles onto a Calcium Sulphate screed you must ensure that all laitance, dust, dirt or any other loose surface material incompatible with the tile adhesive must be removed.

Do you have to seal screed floor before tiling?

The sealants act as a water barrier that helps the adhesive maintain its bond between the tiles and the surface. It's essential to seal the screed floor before laying tile. This prevents it from affecting the tiles.

What is anhydrite binder?

First lets look at the basics, anhydrite is a binder used in sand and cement which has been rapidly adopted to replace the more traditional binders. It has revolutionised screeds used in the construction market.

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. Or at stress points such as doorways and corners.

How thick should 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.

What is a floating screed?

Floating screeds are unbonded screeds but generally laid on a layer of insulation. They are mainly used in structures with underfloor heating or for situations where acoustic or thermal insulation is needed. It requires a thickness of 50 – 65mm, even up to 75mm for heavily-loaded floors.

What is the best screed for underfloor heating?

It is important to remember that there are various types of underfloor heating available but it will usually take the form of electric heating cables or warm water pipework. Whether the project is commercial or domestic, a new build or a renovation, cemfloor liquid floor screed is the best for underfloor heating.

Should the floor feel warm with underfloor heating?

As a general rule of thumb, your heated floor shouldn't feel hot - it should just not feel cold.

Should you leave underfloor heating on all the time?

It is advised that in the depths of winter, an underfloor heating system should be kept on at all times. Although it should be at different temperatures depending on usage and activity in the house. This is because underfloor heating can take two to three hours to warm up, so it is best to not completely turn it off.

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.

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.

What is the meaning of Laitance?

Definition of laitance

: an accumulation of fine particles on the surface of fresh concrete due to an upward movement of water (as when excessive mixing water is used)

What causes Laitance in concrete?

Either adding excess water to the mix, or inadequate curing will cause laitance. Laitance is the weak, milky or powdery layer of cement dust, lime and sand fines that appear on the surface of concrete.