Removing Painted Floor Lines from Concrete

Companies need paint lines removed for a variety of reasons.  Food facilities cannot have flaking paint, the building is sold and the new owner needs the lines removed, or a new production cell is installed and the old lines are confusing the traffic pattern for forklifts or pedestrian traffic.

Floor Lines and Scraper

One of the questions we get asked frequently is whether we can remove the floor lines painted on warehouse or factory floors.  Like much of the world of surface prep, the answer is a qualified “MAYBE”.

Like every surface preparation job, “maybe” is dependent on what the customer’s final surface needs are upon completion of the job.  I have four factors, in no particular order, that I consider when quoting a line removal job.  This is my general process, plus there are some unique things about every facility that might add to this list.

  1. What kind of paint is it, how old is the paint and how much traffic has been on it?
  2. What is the surface condition of the concrete underneath the paint?
  3. Are there limitations on what techniques or media types we can use to remove it?
  4. Does the line removal need to be complete, or is there a tolerance for a minor amount of residue?

If the customer wants the floor to look like the lines were never there, they are almost certainly out of luck.  It is almost unheard of to be able to remove lines and restore the floor to an as new condition.

 If they need all paint removed but the ghost of the lines remains, that can be doable.  Depending on the paint type and how the floor was sealed, if at all, we have had success in getting these lines off the floor.

If a few percent of the really stuck on paint is acceptable, that is almost always a situation where we have had great success.

As always, the four rules of surface prep apply, Temperature, Agitation, Caustic and Time.  In this case the lines can be heated, we can use dry ice or other blast media for the agitation, paint thinner or solvent for the caustic, and the time is dependent on all the factors I consider at the individual job site location.

For the agitation phase, and of course depending on the facility, I generally recommend using dry ice blasting.  Unless the building is being rehabbed, I find that the other blasting media types such as corn cob, walnut shells or baking soda are too messy and too damaging to the concrete.  I have heard people say that dustless blasting systems can do this, but I have not found any instance where the water mixed with crushed glass on concrete didn’t create a giant mess and a fair amount of damage to the concrete under the lines.

We use a three to four step method on dry ice blasting these lines.

  1. Direct dry ice blasting to remove loose or paint that is not firmly adhered. Agitation!
  2. Scraping using a floor knife or similar tool. More Agitation!
  3. Heating the line with a torch flame or electric heat gun. Temperature!
  4. Paint thinning chemical, if permissible.  Caustic!
  5. Hope and prayer. Time?

Through a little testing, you can quickly determine if dry ice blasting directly is going to work without any of the other alternatives. If this works, it will be fast and cost effective, but there are not many jobs I have found that will do this by itself. Also, even though it’s not abrasive, the dry ice can and will damage the concrete floor as it will remove some of the aggregate on the surface and that leaves its own outline, so care needs to be taken when testing and production blasting.  See step D above.

If we’re lucky, the floor underneath is properly sealed with a high quality floor sealer.  Note to people laying down floor lines.  Sealer underneath is a worthwhile expense!  The sealer usually is good enough to eliminate the risk of concrete damage from the blasting, but not always.  See step D above, again.

If dry ice blasting alone doesn’t work, then we try heating it.  If it’s an industrial facility, a propane blowtorch wand works great to rapidly heat and soften the paint, then dry ice, at -109 degrees, can usually make good headway because the softened paint contracts rapidly with the dry ice and releases the surface tension of the paint for faster removal.  In a food facility or where there is no ability to use an open flame, then a powerful electric heat gun can often work, just more slowly than the flame type.

Floor Lines removed with Dry Ice Blasting

If the floor is not sealed, and paint thinning is a permissible option based upon local regulations and the type of facility involved, we can add a thinner to the mix to loosen the paint and assist the dry ice.  This adds the expense of disposal of the thinner rags after we are done, and the paint removed may also require special handling, but in some cases it’s a necessary evil.

Another method that can really improve speed, but does present its own challenges, is using a shotblasting machine (or sometimes a rotating head scraper) that recycles through a dust collector a stream of steel shot to peen into the concrete and remove the painted lines. If you want minimally floor damage, this has some risks as you will take off up to 1/8″ of the top concrete layer, and keeping that minimized can be difficult. If you are going to reseal the area, this works pretty well and also fairly quickly. As with anything there are some trade offs with tight spaces and around posts or bollards for example, where the equipment cannot get close enough to be used.

Finally, we usually find that at least some scraping is needed.  For example, where forklifts have really pushed it into the surface, a little scraping and elbow grease is a quicker solution than slowly blasting away with incremental progress.  Using a steel shotblaster still usually requires some scraping around posts or in corners or narrow opening areas that the equipment cannot access.

Really thick paint, or epoxy, can also need the extra step of scraping.  Speed is the defining factor, we usually charge by the linear foot, so time is money.  If it’s faster to heat and scrape, then we do that, if it’s a scrape only job, so be it.  Sometimes we use dry ice, a shotblaster plus scraping. Every job is different.

Your job may be easier or more difficult, the biggest factors are still the type of paint, sealed or unsealed concrete, the final concrete finish you need to have and the budget for the project.

In conclusion, floor lines are a challenging surface prep task, and it takes some real work to remove them, but it usually can be done.