Can you polish an existing concrete floor afterwards? That is possible with a suitable floor, but it is a different process than polishing fresh power-trowelled concrete. With a hardened floor, it involves grinding and possibly further polishing. The condition of the concrete determines what is achievable.
Polishing fresh power-trowelled concrete
The finishing is done during curing, at the right moment after pouring. You cannot simply repeat that work years later using the same method.
Polishing existing concrete
The hard surface is mechanically treated. The desired appearance, the condition of the floor and a test area help determine which treatment is appropriate.
The original question: an uneven basement floor of 140 m².
A customer had a concrete basement installed about four years earlier. During pouring it started to rain and the agreed finishing was not carried out. The basement floor remained uneven. Could that floor still be polished, or was another finish wiser? It concerned approximately 140 m², divided over five rooms.
That question contains two different desires: a flatter floor and a more attractive surface. It is important to assess these separately. A treatment that changes the gloss does not automatically resolve height differences. Also, the difference between one open space and five smaller rooms matters for the execution and accessibility.
The original advice mentioned dry grinding and a tiled floor as possibilities. Tiles can be a sensible choice for such a basement, but without assessing the substrate, available build-up height and desired finish, we cannot state that this is always the best or cheapest solution.
What exactly does polishing afterwards mean?
Mechanical polishing involves treating an existing concrete floor with suitable grinding and polishing tools. The successive operations and the extent of material removal partly determine the result. The appearance therefore also depends on the floor already in place: the concrete mix and the existing condition form the starting point.
Grinding can make aggregates visible. A more strongly exposed aggregate gives a different appearance than a floor with a more closed cement surface. Therefore, discuss in advance what result you expect. A reference photo of another floor is useful, but a test patch on your own floor provides more certainty. Husqvarna describes various grinding and polishing systems for this purpose..
How does polishing an existing concrete floor proceed?
Polishing is done in successive operations. Which steps are necessary depends on the existing floor and the agreed final appearance. For example, a coarse grinding step is different from the final operation that makes the surface finer and shinier.
Assessing and preparing
The substrate, existing finishing layers and damages are examined. A test patch helps to determine the achievable aggregate pattern and appearance.
Grinding and refining
Suitable diamond tools work the concrete. Finer steps refine the traces of the previous treatment to the chosen finish.
Finishing and maintenance
The floor is cleaned and the result assessed. You receive agreements about any protection, commissioning and appropriate maintenance.
Some polishing systems also include filling pores and a concrete hardener as part of the treatment. The product and the timing of application are part of the chosen system. The Husqvarna grinding and polishing guides show that different final finishes each have their own working method.
A concrete hardener and protection against stains are not automatically the same. Therefore, also read our explanation about concrete hardener and protecting a concrete floor. There is no general waiting time of 24 hours for every treatment: the products used and circumstances determine when the space can be used again.
Also finishing edges, corners and door openings
An open floor surface is easier to reach with a large machine than a narrow strip along a wall. Edges, corners, columns and passages therefore require separate attention. For edge work there are smaller machines and adapted grinding and polishing tools. The transition to the large floor surface is part of the assessment of the final result.
Discuss before execution whether skirting boards, fixed cupboards or other obstacles limit accessibility. Also indicate such places on the floor plan. In a basement with five rooms this plays a bigger role than in an empty hall of the same surface area.
Have the quotation specify which edges and connections will be included and which areas remain accessible. This makes proposals more comparable and prevents only the easily accessible central area from being discussed.
Wet or dry grinding: what does that mean for your space?
The choice between wet and dry working is part of the chosen grinding system. Not every machine or tool is suitable for both methods. Therefore, discuss not only the desired appearance but also how the contractor collects dust, water and grinding residue.
Dry grinding
Dry grinding requires suitable dust extraction on the machine. Vacuuming only afterwards is not the same approach. The extraction, connections and collection must fit the equipment and the dust released.
Wet grinding
With a suitable wet method, water binds the grinding dust. This creates grinding slurry that must be collected and removed. Adding water to a machine intended only for dry use is not an alternative.
Husqvarna describes the intended equipment for dust and slurry collection. The chosen method therefore also changes the preparation of the space and the way it is delivered clean.
Polish a concrete floor yourself or have it done?
Hiring a machine does not guarantee the final result. You also need to be able to assess which treatment the floor can tolerate, which tools fit, and how the transitions and edges are finished. Have a test area assessed before tackling a complete living space. This way you can compare the expected result with professional execution, including preparation, edge work and cleaning up.
First investigate, then choose a finish
When making an enquiry, do not only state how many square metres the floor measures. The reason for the renovation is at least as important. Is the floor rough, are there local height differences, is the appearance mainly disturbing or do you want to give the space a different purpose?
- Use: is it a storage cellar, garage, workspace or living space?
- Current condition: are there cracks, loose spots, old finishing layers or visible repairs?
- Layout: how many rooms, doorways, corners and hard-to-reach strips are there?
- Joints: how much space is there at doors, stairs and adjacent floors?
- Expectation: do you mainly want a usable floor or should the visible concrete have a certain appearance?
For assessing flatness, a measurement counts, not just a photo. Buildwise explains how the flatness of a floor is checked.. The applicable tolerance depends, among other things, on the type of floor and the agreed finishing grade. It is therefore not advisable to use one general figure for every existing concrete floor.
Grinding, a new finish or tiles?
| Possibility | What should be discussed beforehand? |
|---|---|
| Grinding and polishing | Suitability of the existing concrete, desired grain pattern, test area and accessibility. |
| An additional finishing layer | Compatibility with the substrate, required preparation and available build-up height. |
| A tiled floor | Suitable substrate, height at doors and stairs, layout and total floor construction. |
Compare proposals for the same final expectation. A price for only a surface treatment is different from a proposal that also includes substrate preparation, local repairs and a new floor finish. Have it clearly described what is included and which visible properties of the existing floor can be preserved.
Does polishing also change the colour of your concrete floor?
If you mainly want a different colour, indicate that before choosing grinding or polishing. Polishing an existing concrete floor is a different process than incorporating pigment into fresh power-trowelled concrete. Therefore, do not expect a grey floor to automatically become an evenly black or white floor through polishing.
Preserving the existing concrete
Discuss what appearance of the existing floor is achievable. A test area helps to assess the visible structure and finish before the entire space is tackled.
A different colour as a starting point
A coloured coating or other finishing layer requires a separate assessment. That produces a different result than polishing the existing concrete itself. Substrate, use and desired maintenance also determine which approach is suitable.
Waxing or impregnating is also a separate treatment. It is not a substitute for choosing the colour or levelling the floor. Read more about protecting, impregnating and sealing concrete floors.
What determines the price of polishing afterwards?
A fixed price per square metre without knowing the floor provides little certainty. For the basement in question, not only the 140 m² are relevant, but also the distribution over five rooms and the desired restoration. Request an assessment based on overview photos, detail photos, a simple floor plan, and the desired finish. If necessary, a site visit or trial treatment will follow.
Also ask how the contractor prepares the space and leaves it clean. Access for machines, protection of adjoining spaces and dealing with dust or grinding residue are part of the work agreements. The floor remains a work zone during execution; coordinate the use of the spaces with the chosen treatment.
Frequently asked questions
Can the floor be finished again with a polishing machine?
Polishing fresh power-trowelled concrete and treating hardened concrete are different processes. A floor that has been hard for years is no longer in the phase in which the fresh concrete mass is finished. Therefore, have it assessed which grinding or finishing technique suits the existing condition.
Does the entire floor need to be replaced?
That does not automatically follow from a rough or undesirable surface. First have the existing floor assessed and compare the possibilities to preserve it. A decision about replacement requires more information than just a photo of the top.
Is polishing afterwards the same as maintenance?
No. Cleaning a floor or performing maintenance treatment is a different matter than mechanically working the concrete. Therefore, describe what is wrong and what result you are seeking before choosing a treatment.
Have your existing floor assessed.
Send photos, the surface area, the layout and your expectations. This way, it can be specifically assessed which next step is meaningful for your concrete floor.
Discuss your concrete floorPlanning a new floor? Then also consider the possibilities of residential concrete and discuss the finishing before pouring.
Can you polish an existing concrete floor?