Decorative epoxy flooring - the polished concrete and warehouse looks

You’ve been asked to do a polished concrete or “warehouse” look for a client with your decorative epoxies - what do you need to know?

The traditional form of polished concrete involved 10-12 passes with a diamond grinder to hone the concrete into a smooth, glossy surface. While this type of flooring has been extremely popular in recent times, not every slab can be polished successfully and pricing is typically at the higher end. Because of this, a somewhat simpler and more cost-effective alternative can be done through the use of clear epoxies that rely on the resin to flatten the surface instead. This can be a very basic “grind and seal”, which results in the more rustic warehouse look, or, with the right product and thicker films, it can create a mirror-like, genuine polished concrete look.  

Either way, if you think the idea of slapping a clear epoxy over concrete is a walk in the park, don’t be so sure! Believe it or not, there are few traps that regularly catch contractors out when taking on jobs like this.

Change your preparation goals

First and foremost, the polished concrete look and warehouse look will benefit from a slightly different approach to surface preparation. The natural inclination for many contractors is to whack a big, heavy grinder onto every slab and keep going until it’s completely flat. While there’s nothing wrong with that thinking as far as thorough preparation is concerned, ripping the tops of every high spot results in patchy, inconsistent aggregate exposure that rarely looks great in the final product. Instead, you want a grind that follows the contours of the slab and only removes the top layer across the entire area. An example of this type of thing is something called Diamabrush, which uses diamonds on flexible brushes to do just that.

Clear epoxies aren’t dead basic!

Ok, so you have a freshly prepared slab with a relatively even “salt and pepper” appearance. From here many contractors would simply mix up their clear epoxy, pour it onto the floor to roughly spread out, and then start back rolling. The problem with this practice is you can often see a dark patch form under the thicker sections of the poured clear epoxy - what I call the “pour line”. You can never fix such a blemish if it shows through the final coat, so you need to prevent it by changing your approach when working with clear epoxies, i.e. working from a roller tray is generally a safer option on the first coat.

This type of staining effect can also cause headaches in other situations, especially when applying in warmer weather. In these instances, the hotter conditions lead to large variations in the viscosity of the clear epoxy, i.e. freshly mixed product is thin and soaks into the slab easier (looks darker), whereas older product that has begun to gel is much thicker and doesn't penetrate as much (looks lighter). The result of this viscosity difference is the appearance of noticeable bands across the floor corresponding to the rolling pattern used, and is particularly visible where an old mix meets a new one. Once again, there’s no quick fix and prevention through measures such as smaller mix volumes is the only way around it.

Another potential trap when working with clear epoxies is the formation of “holidays” or, in simple terms, missed spots. Unlike the staining that happens on the first coat, holidays are more common in latter coats when the finish is darker and the clear epoxy isn’t as easy to see. Unfortunately these defects always have a habit of standing out much more the next day and can only be rectified with extra coats and extra cost. I’ve found the use of low-level lighting to be an effective way of reducing the number of misses, however there’s no substitute for working carefully and using a slow, methodical approach to application.

Your clear epoxy must be capable

The final point I want to make on the polished concrete look and warehouse look is an important one: you have to make sure your clear epoxy is actually capable of delivering the finish you’re after. The main focus in this sense is how well it flows/levels and the gloss it can achieve. The warehouse look is pretty forgiving and many clear epoxies will be suitable for that type of finish, however, I know from experience there are only a handful of clear epoxies that can make a good fist of a high-end polished concrete look. Regular readers of Epoxy School will know I always come back to doing homework on products before committing to any projects and it certainly isn’t any different here!

Take care and keep smiling,

Jack

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