If you have ever walked across a perfectly flat, smooth floor before the tiles went down, you have probably seen screed in action. People often mix it up with concrete, but the two do very different jobs. In simple terms, ready mix screed is a factory-batched blend of cement and fine sand, delivered to the site ready to lay.
It goes on as a thin, smooth layer that levels the floor. Concrete, by contrast, is the tough, structural stuff that holds buildings up. So one finishes a floor while the other builds the base. Here is exactly what sets them apart, and when to use each.
What is Ready Mix Screed?
Ready-mix screed is a smooth, factory-mixed layer of cement and sharp sand, delivered ready to lay over a floor. Crews spread it to create a flat, even base for the final flooring.
Definition & Purpose
Screed is a thin, smooth layer laid over a concrete subfloor or underfloor heating. Its job is simple: create a flat, level surface that flooring such as tiles, wood, or vinyl can sit on. Without it, floors would feel uneven, and finishes would not last.
Screed is mainly used to:
- Level out dips and high spots in a subfloor
- Cover and protect underfloor heating pipes
- Create a clean base for tiles, wood, vinyl, or carpet
Composition
Screed is made from a few basic ingredients, with additives used only when needed. Typical screed contains:
- Cement, which binds the mix together
- Sharp sand, the fine aggregate that gives a smooth finish
- Water, in carefully measured amounts
- Additives, sometimes included for faster drying or better flow
This means the recipe stays simple, yet small changes can tune it for speed or smoothness.
Types
There are three common types of screed, each suited to different jobs:
- Traditional sand and cement screed, a semi-dry mix that is hand-laid and trowelled smooth
- Liquid screed, a free-flowing mix that self-levels and covers large areas fast
- Anhydrite screed, a calcium sulphate-based liquid screed often used over underfloor heating
In addition, liquid and anhydrite screeds suit big, open floors, while traditional screed works well in smaller rooms.
How It Is Produced
Screed is batched and mixed in a controlled factory or on a volumetric truck, then delivered ready to lay. Because the mix is measured by machine, every load comes out consistent. As a result, crews spend less time mixing and more time laying.
Delivery by truck also means large floors can be poured in one continuous, even pass.
How Ready Mix Screed Differs from Standard Concrete
The main difference is the job each one does. Screed is a thin finishing layer for a smooth, level floor, while concrete is a thick, strong material for structures, foundations, and hard-wearing surfaces. The table below sums up the key contrasts:
| Feature | Ready-Mix Screed | Standard Concrete |
| Main job | levelling and finishing floors | structural strength and bases |
| Mix | cement and fine, sharp sand | cement, sand, and coarse aggregate |
| Aggregate size | fine, around 0 to 4 mm | coarse, up to 20 mm or more |
| Consistency | semi-dry or free-flowing | wetter, varies with the job |
| Strength | lower, for a smooth surface | high, for loads and wear |
| Finish | smooth and refined | rough and rugged |
1. Function And Application
Screed finishes and levels, while concrete builds and supports. You lay screed to prepare a floor, and you pour concrete to form the slab, footings, or walls beneath it. Think of screed as the smooth top coat and concrete as the solid frame underneath.
2. Mix Proportions
Screed uses more sand and less coarse material. It runs about one part cement to three or four parts sharp sand, while concrete is closer to one part cement, two parts sand, and three parts coarse aggregate.
3. Aggregate Size
Screed uses fine, sharp sand, roughly 0 to 4 mm across. Concrete uses coarse aggregate, often up to 20 mm or larger, which is what gives it bulk and strength.
4. Mix Consistency
Screed is either semi-dry, so it can be trowelled, or free-flowing for liquid types. Concrete is a wetter mix, with the slump adjusted to suit the pour. The wetter the mix, the easier it flows, but the longer it can take to set.
5. Strength And Durability
Concrete is built for strength, carrying heavy loads and constant wear. Screed is built for a smooth, level finish, so it sits on top rather than holding weight on its own. That is why screed should never replace a structural concrete slab.
6. Finish And Texture
Screed leaves a smooth, refined surface ready for floor coverings. Concrete is rougher and more rugged, made to last under pressure rather than to look neat.
Why Choose Ready Mix Screed Over Site Mixed Screed
Factory-batched ready-mix screed beats site-mixed screed on consistency, speed, and reliability. When every load is measured the same way, the finished floor turns out far more predictable.
Consistency And Quality Control
Factory batching keeps the mix the same every time. Machines measure each ingredient, so the screed performs to a known standard load after load.
Time Savings
Ready-mixed delivery cuts out hand mixing on site. Crews simply lay the screed as it arrives, which speeds up the whole build.
Reduced Waste
Measured batching means less wasted material and lower water use. You order what you need, so little is left over to skip.
Better Performance
Consistent mixing lowers the risk of screed failure. Site mixes can vary from batch to batch, which is a common cause of cracking and weak spots. Put simply, ready-mixed delivery takes the guesswork out of the mix, so the floor ends up stronger, flatter, and finished faster.
Related Considerations
Some practical points help you plan a screed job well:
- Thickness: Screed layers are usually much thinner than structural concrete, often only a fraction of the depth
- Drying time: Screed can set quickly, but full drying depends on the type, thickness, and site conditions
- Underfloor heating: Screed is a popular choice over heating pipes, since it spreads warmth evenly
- Loading: Wait until the screed is strong enough before walking on it or laying finishes
As a rule, allow plenty of drying time before laying the final floor, especially with thicker screed.
Takeaway
Ready mix screed is a factory-batched finishing layer, while standard concrete is a structural material with coarser aggregates and far greater strength. Choose screed for a smooth, level base, and choose concrete to carry weight and build the structure itself. Match the material to the job, and the floor will look right and last.
If you need screed that turns up ready to lay and level, Pro-Mix Concrete delivers fresh floor screed across London and the surrounding counties, batched on volumetric mixers so every load is consistent, and you only pay for what you pour. From fast-drying liquid screed to mixes made for underfloor heating, with same-day delivery and friendly expert advice, this supplier helps your floors come out smooth, level, and ready for whatever goes on top.
