1. Must-knows about self-levelling screed

1.1. What’s screed and why do we need it?

When talking about construction or remodelling, sooner or later, the word ‘screed’ will come up. Screed is one of the crucial elements in finishing work, so before you start constructing or remodelling, it’s good to know what it actually means and what it’s used for. Actually, screed has a very broad meaning; it’s an umbrella term encompassing different processing and application methods. Simply put, we can say that it’s a modern and updated version of cement screed, which used to have wide application in construction, as the floor’s final layer.

1.2. Screed use

Screed is mostly used for levelling final floor surfaces, although there are types used for surfaces which are not perfectly level, e.g. because of a drain, and they’re called slope screeds. In addition to forming the floor’s final layer, some types of screed can also be used for bonding or forming a substrate in case of greater mechanical loads. So, screed’s primary function is to serve as a substrate over which flooring is laid. It forms rather thin substrates, with a thickness of around 5 cm.

Self-levelling screed allows up to 25% less floor thickness (around 3.5 cm) than does cement screed, which requires 5 cm on average.

1.3. Types of screed

Every market and its manufacturers have a range of various screeding compounds, which differ in mechanical properties and the application method. Two basic types of screed are dry and flowing screeds, but there are also self-levelling screeds (a type of flowing screed), dry lay screeds (a type of dry screed), and rapid drying screeds, and types used for insulation, mechanical and industrial types, etc.

2. Self-levelling screed

2.1. What is self-levelling screed?

Self-levelling screeds are flowing screeds. This is a mix which flattens across the floor, without any need for further levelling. This type of screed works particularly well when combined with tiles, parquet, and laminate flooring.

2.2. When to use self-levelling screed?

This type of screed makes a great base for different types of flooring, including tiles, parquet, and laminate flooring. In this respect, its properties stand way above other types. 

3. Advantages

Self-levelling screed has numerous advantages, which make it one of the most popular types on the market. However, we do suggest you consult a professional before you buy anything, as they’ll be able to recommend the exact type which is suitable for your situation.

3.1. Firm substrate for your feet

Floors should always be firm, non-slippery, and enable a seamless walking experience. If you choose to go with just screed, without any flooring covering it, all the more reason why you need a level, stable, and adhering substrate. Screed is usually used as the final layer in workshops, garages, pantries, some public institutions, and sometimes even in living rooms in industrial style homes. Self-levelling anhydrite screeds will give a smooth area, and what’s more, they’re harmless to health and the environment. This type of screed yields a smooth and even texture, which doesn’t require any additional levelling, but maybe just some final polishing.

3.2. Less noise

Application of self-levelling screed results in a thinner floor. Self-levelling screed allows up to 25% less floor thickness (around 3.5 cm) than does cement screed, which requires 5 cm on average. This is particularly useful when remodelling old buildings, where floor thickness can’t be modified. Also, if you want to make your floor more soundproof, you’ll get 1.5 cm of space to install a soundproofing solution. If you want to add thicker flooring as well, there’s room for this, too.

3.3. Self-levelling screed takes less time to dry

One of the most striking advantages of self-levelling screed is that it dries a lot faster than all cement screeds. There are many reasons for this, but the most obvious one is the thin layer. Another reason is the composition of the mix, since ingredients differ to some degree to those in cement screeds. Rapid drying particularly comes in handy if you’re on a tight schedule. Self-levelling screed’s walk-on time is just 24 hours! Drying time is short even during the cold weather, so you can apply it at any time of the year.

3.4. Great mechanical properties

Like all types of screed, self-levelling one, too, has great mechanical properties, so it can withstand a great pressure and all kinds of loads, and it’s also got excellent flexural and ware resistance. Due to its specific composition and granular structure, self-levelling screed has more flexural resistance than conventional cement screeds. This is another advantage that comes with its small thickness. Screed’s thickness can be smaller despite the same loads. Its thermal conductivity is amazing. Another great property is that it doesn’t expand or contract, which prevents lumps, unevenness, and defects around the edges. In smaller rooms, it can be applied without expansion joints.

4. Screed installation

4.1 Easy & quick application

Although this installation is quite simple, we recommend you leave it to professionals. The mix must be dense enough and lump-free, so you’ll need experience and skill to make one. The pouring process also requires professional equipment and a trained eye to precisely determine the quantity and quality, and the application method. Self-levelling screed enables quick, efficient, and reliable work when constructing, remodelling, or repairing. No additional reinforcement is required, because, unlike other types of screed, the self-levelling one has less expansion/contraction.

4.2. Self-levelling screed mix

The self-levelling screed compound which can be bough in building supplies shops or DIY shops is available in powder, with all ingredients already included. It comes in plastic containers or bags, and it should be mixed with water by a power mixer according to the manufacturer’s instructions. A self-levelling screed mix contains gypsum and water. Gypsum is a water-soluble powder substance containing calcium sulphate. Apart from gypsum, which we can also call cement, the mix also requires an aggregate, typically gravel or fine sand. This compound is then mixed with water at a ratio recommended by the manufacturer, until you get a fine, smooth, lump-free mass, which is then applied through a hose.

4.3. Floor and wall preparation

Before you start the work, make sure you prepare the floor properly and protect wall edges and corners. The floor structure must be completely dry and firm. Once the structure is prepared, first lay down the soundproofing material. The next step is sealing the wall-floor junctions with special elastic materials. After this, lay a PVC foil over the soundproofing insulation, which will make your floor completely impermeable, which is a precondition for screed installation. The overlaps between separate pieces of foil must be at least 10 cm. Once the entire floor surface and wall junctions are sealed, you can lay the underfloor heating system if you have one. After all this is done, pour the screed, and it’ll spread and flatten on its own.

4.4. Levelling

When pouring screed over a room, even though the main advantage of this type is that it’s self-levelling, make sure the mix is evenly spread. To ensure you get a completely smooth and even floor, start pouring the mix at the point where you want the thickest layer, and at the end, level it with a timber piece.

4.5. Drying

A distinct advantage of the self-levelling screed, compared to other types of screed, and especially standard cement screeds, is its short drying time, which means it can be installed even during the cold/rainy seasons. This type of screed can be walked on after only 24 hours.