January 28, 2020

This Is How You Polish A Floor Screed

A floor screed cannot normally be polished to a smooth finish, so here is our guide to achieving a polished floor screed using an overlay system.

An example of a sand:cement floor screed

If you’ve just discovered that you have a floor screed in your home or business premises, you’ll probably have a thousand thoughts and questions running through your head - ‘what am I supposed to do with that?!’ or ‘that’s not pretty, I’ll have to cover it up’ tend to be amongst the most common. We don’t blame you. Plain screeded floors are rarely attractive and are after all, not really designed to be seen. How do you know what flooring options are available to you? Normally, you’ll be wondering with what you can cover them up with but if you’ve heard of concrete polishing or experienced the grinding and polishing of concrete the burning question may be ‘how to polish a floor screed?’

A screed slab is usually hidden beneath ceramic tile, hardwood floors, natural stone or a nice thick carpet. But when exposed, they look drab, dusty and often dirty. They look unfinished, like there is something missing and this is why the first reaction is usually to cover it over with something much more attractive.

What is screed?

Often, because the majority of people won’t realise that there is a difference between concrete floors and a screed they may incorrectly surmise that they have a concrete floor in place and not a screed - it is true the two floors can look remarkably similar even though there are some marked differences between the two substrates.

Screeds are usually a mixture of sand, cement and water whereas concrete is made up primarily of sand, cement and aggregates. Due to the absence of aggregate, screeds tend to be softer and a lot less abrasion resistance than concrete is, it also tends to have a much dustier surface than a clean concrete may have.

There are a lot of new screed products on the market today, so it’s likely if your screed floor was laid recently that it may be one of the more modern ‘liquid’ screeds. As the name suggests, these are much more liquid in substance than a sand:cement mix which makes them much easier for a contractor to lay. As these can be laid very quickly and flow into place easily it makes them the substrate of choice for many contractors as they’re much less troublesome than other mediums, such as concrete.

Perhaps you are thinking, how can I tell if I have a concrete or screed? If only the answer was a simple one but like everything that is cement related, it’s complicated! I would suggest a visual inspection in the first instance for larger stones - are they visible in the floor surface? If they are you definitely don’t have a screed as usually only smaller pebbles will be visible here.

Another little trick is to take a table knife and run it along the surface of your floor to see if you can leave a noticeable scratch in the surface. While this test is not foolproof as a rule if you can mark the surface with the knife it’s more likely to be a screed than concrete flooring.

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Can You Polish A Floor Screed?

So, let’s get to the million dollar question! How do you get a polished screed floor? In our opinion screeds cry out for a thorough polishing although sadly this cannot be done directly. This is to say, grinding the surface is unproductive and we are unable to polish it with our diamond tools as we would with a concrete slab. So, what flooring solutions are open to you?

Your only option if you find yourself with a screed floor is to cover it over but that doesn’t mean you have to forego the beautifully polished floor that you’ve been planning and have long imagined. In fact, you may find yourself looking back in time and actually being thankful that you’ve got a screed floor and not a concrete one as you’ll be much more in control of the results that can be achieved with it.

Screed floors can be transformed into polished flooring with the application of a concrete overlay or microcement. In short, while these are two slightly different options they are both thin concrete toppings that are placed over the top of your existing floor. Both options can be coloured in accordance with your colour scheme or fixtures and fittings and neither will raise the existing floor height significantly.

Best results will always be gained from a smooth, flat, hard and well laid screed although it certainly is true that overlays are an option to improve rough or uneven screed surfaces. If you’re having a screed laid with a purposeful view to having an overlay applied, then we’ll be more than happy to give you laser screed recommendations and a specification that you can pass to your concrete contractor in order to achieve the best finishes.

You Could Use A Concrete Overlay Over Your Floor Screed

A concrete overlay is applied at around 10mm in thickness and pours down like thin liquid concrete that binds to the surface. This dramatically improves the surface strength and the biggest draw for a lot of clients is that a concrete overlay is mechanically diamond polished. Yes! A PROtop overlay is actually a genuine polished concrete floor!

A PROtop overlay can be coloured easily to fit in with your vision. It can be textured with decorative aggregates or even glass chippings if you want to do something a little different, get really artistic and create a look reminiscent of a terrazzo floor. PROtop can then be finished to a matt, satin or high gloss sheen.

Or Maybe A Microcement To Create A Different Look?

A microcement is around 2-3mm in thickness and applied in multiple thin layers with a small hand trowel. This creates a seamless surface that is reminiscent of a power trowel concrete floor finish like our InfinityFloor Cream. In fact there are many clients that choose our Microfloor instead of opting to lay a power trowelled concrete that has a tendency to be difficult to lay. While our Microfloor is an incredibly hard floor covering, a microcement tends to inherit most of its compressive strength from the substrate below so if your screed is soft we may suggest that an overlay is a better option.

As this is laid so thinly by hand, there are no aggregates incorporated in the floor therefore this produces the ‘no stone’ appearance that is so popular right now. Just as with the PROtop overlay, our Microfloors are fully colourable but due to method of application not mechanically diamond polished. However a good level of gloss can be achieved so there are still plenty of choices of finish.

At CARRcrete we manufacture both our PROtop overlay and PROtop Loft microcement bespoke on a client by client basis. We feel by doing this we can focus on the individual requirements of each floor and each client and in return, each client we see ends up with a unique polished concrete floor unlike any other. It really is a win win situation for all and infinitely more attractive than the screed floor you started off with!

All CARRcrete overlays are completely compatible with water fed underfloor heating systems and have been designed to be flexible and expand alongside the screed substrate when the heating is on, to minimise the risk of cracking. There are special rules to follow for commissioning your underfloor heating and we will give you full details of this to help you get the most from your flooring choice.

What Kind Of Screed Do You Have?

So may I ask you, what kind of screed do you have? Is it an old sand:cement screed that was laid painstakingly by hand, recently found beneath a carpet or tiles? Or one of the new liquid screed systems that was pumped through a hose and completed in what seemed like just a few seconds?

The most important factor we need to determine is, is it a cementitious (containing cement) screed? Liquid or not, a cementitious screed offers a lot less complications from our experience. The anhydrite or hemihydrite screeds whilst new, economical and easy to install pose far too many complications when overlays and toppings are to be applied.

These types of screeds tend to be softer than the screeds containing cement and also have a tendency to withhold moisture for long periods of time. This is not a good thing when adding another layer of product as you don’t want any moisture to gather between these two layers. This may and probably will cause problems with potential delamination in the future.

There are a few ways you can determine the difference between a sand:cement screed and a liquid screed. If the floor was recently laid the easiest thing may be to ask the contractor about the product and it’s makeup, they should have a record of what they ordered.

Failing that, if you look at the surface a sand and cement screed will often look like sandy old concrete that dusts easily and is relatively easily damaged with something like a screwdriver. Running the implement across the surface will release dry dust and debris.

An anhydrite screed looks more plaster like, lighter in colour and usually free from sandy dust. A fine film of laitance (a weak, sometimes creamy surface layer) is often visible and the same screwdriver test will result in damp dust-like flooring material falling away. The dust is similar to fine talc quite tightly bound to the surface.

There are cementitious liquid screeds on the market. These often show the same consolidated surface texture but are more grey in appearance than the oatmeal coloured anhydrite screeds.

Let’s Look At Some Key Points

  1. Floor screeds are designed to be covered
  2. You cannot diamond polish a floor screed as it is
  3. You need to determine what type of screed you have
  4. Cementitious screeds pose fewer complications
  5. We have products to cover and overlay a screed
  6. Using an overlay allows you to alter the look of the floor

A Screed Just Does Not Cut It

Unfortunately as we have determined, in its natural state a screed cannot be polished.

There are companies and manufacturers out there that claim they have a polishable screed but in our years of experience we have never found one, and we’ve tried! Simply put screeds are not strong enough to resist the abrasion from diamond tooling, so they cannot be mechanically polished. All the sand and finer ingredients (typically chalk, ash or filler) of the screed mix simply fall out and you are left with a sand paper like surface that breaks apart, scratches easily and thirstily absorbs dirt.

Applying a thick sealant or resin also does not work well either; screeds are so porous that they simply drink the applied product and leave a semi gloss finish that is still easily damaged – neither practical for use or aesthetically pleasing.

All Is Not Lost Though, We Have A Solution

Fortunately there are products that can be used to cover a cementitious floor screed. Products that can transform the look and feel of a screed into something that is much more durable, attractive and easily maintained than other types of flooring. We all want something that is easy to clean, don’t we? The bare sandy surface that spreads dust and traps debris can be banished with the application of an overlay or topping.

What are these magical products I hear you ask? Overlays and toppings are broad terms for products such as our CARRcrete PROtop concrete overlay and CARRcrete MicroFloor microcement


A floor screed whilst pretty boring to look at still needs love. Our PROtop and MicroFloor products are more than capable of offering your dusty floor screed the much needed love, care and attention it so desperately needs.

Our overlays give you the chance to redesign your floor, create new textures and tones and choose a colour that you like. Add sparkle with glass chippings or throw in some marble, granite or limestone to create a finish reminiscent of terrazzo.

The benefits of a polished floor screed through the application of our concrete overlays and toppings is more than just aesthetics. Both products increase the compressive strength and abrasion resistance of a screed surface. The sealer that is applied offers easier maintenance and cleaning whilst still retaining breathability of the whole floor structure. All that is needed to keep it clean is a daily dry mop and a weekly clean water damp mop, it couldn’t be simpler.

Barrier mats are recommended with all decorative concrete and overlay systems as these will remove grit and contaminants from outside that are easily transported inside on the soles of our shoes. Believe me, these will certainly help lessen any wear and tear, especially in high traffic areas.

You Can Polish A Floor Screed By Using Our Products

Both of our products were engineered and designed by our MD Dave Carr who is widely regarded as a leader and innovator in his field. All our products are manufactured to order in the UK using a unique blend of high quality cementitious binders, recycled media and premium polymers. In short they are the most advanced and eco friendly concrete overlay products currently available on the market today. 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.

Dave and his team at CARRcrete apply both products to newly laid slabs and existing floors that meet our suitability criteria. We’re always happy to help if you have any questions or queries regarding the products themselves or the suitability of your premises for an overlay. Please do submit an estimate request or contact Simone our Contracts and Customer Service Manager directly. We will be able to guide you the process of covering a screed with our overlays.

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