How to prepare a concrete floor for painting.

Concrete Floor Preparation

acid etching your concrete garageSurface preparation is THE most important part of getting a long lasting coating.  Your epoxy coating needs something to bind tightly to so that it wont peel off.  If you dont prepare and clean the surface properly this may cause the film  to bind to dirt and dust on the floor and not adhere to the floor as strongly as possible.  Professionals will generally shot blast the floor, which will blast the smooth finish of a concrete floor to give it a somewhat rough surface so that the epoxy will bind very tightly to the floor.   This greatly increases the longevity of the coating, however for a garage floor, using a professional, or hiring a shot blaster may prove to be too costly (though we still highly recommend it).  If the floor is old, you may find that there are grease stains, oil leaking from cars, dirt, dust, mold or mildew and numerous other things that will affect the adhesion.   We need to remove and eliminate as many of these problems before we begin painting.  If the floor is new, remember it must be cured for at least 30 days to allow all the water to escape from the concrete, otherwise this water will push the film off the concrete. Once you have followed these steps, you can then coat with Nugard two pack water based epoxy kit.

  • New concrete must be cured for 30 days.
  • Clear everything out of your garage.
  • Use only when air & surface temperatures are mild.
  • Remove all dust and dirt by brooming and vacuum.
  • Remove all grease or oils by washing with a free-rinsing, alkaline detergent
  • If a coating exists, it will have to be removed, depending on the size of the area:
  1. Small isolated areas: a surface grinder or aggressive sander with 50 grit or coarser sandpaper may do the trick, and then repeat step one.
  2. If most/all of the floor will not return a fizz then it’s suggested that you would rent or purchase a floor grinder to remove that coating.
  • Using a stiff bristled, non-metal brush or broom, vigorously scrub the concrete surface. DO NOT allow the surface to dry. Heavily stained areas or older stains may require additional treatments
  • Thoroughly rinse the entire concrete floor with clean water using a garden hose with a high-pressure nozzle, or a pressure washer.
  • Allow the area to dry. The surface is ready for priming when it feels like medium grit sandpaper and no residue or loose concrete remains.

Laitance is the weak, milky layer of cement dust, lime and sand fines that rise to the surface with over-wet concrete, poor curing or over-trowelling. Why Remove Laitance? The life of a coating is dependant on adhesion to sound concrete. If a coating is applied to laitance, impact from trolleys, forklifts, etc. will cause the laitance layer to delaminate, along with the coating. By removing the laitance layer, coatings can firmly adhere to sound concrete giving much longer service life.

Concrete Surface Preparation Methods

The following is a list of concrete surface prep you can use on your floor to help get the best adhesion for your epoxy coating.  If you don’t want the expense of hiring heavy duty equipment, then you should at the bare minimum use Acid Etching.  The reason for this is Epoxy needs to bond mechanically to the concrete in order for it to adhere properly.  The problem however is that concrete in a garage is always finished to provide a smooth and even surface.  This process reduces the porosity, thus the surface should be profiled to expose the pores so that the epoxy coating can bond to it.  If not, the epoxy will not provide as strong or as long lasting protection.

acid etch your concrete floor Acid Etching Diluted acid is applied to the concrete surface, which reacts with the surface. Afterwards the surface is washed with a high pressure system, the acid neutralised, and then vacuumed. Read how to acid etch your concrete floor.
grind your concrete floor Grinding is suitable to even out the surface of a concrete slab. It can also remove sealers, pains, mastics, and glues from concrete. Diamond grinders are designed to work over large areas. This method provides a smoother finish than scarifiers or scabblers. Read how to diamond grind your concrete floor.
 shot blast your concrete floor  Shotblasting Shot blasting is a one-step process that prepares concrete or steel for coating applications. It cleans and profiles the surface in a single application, and will remove laminate, paint, old coatings, dirt, and other contaminants. The clean surface will bond better with the subsequent coatings after shot blasting is complete. Shot blasting is a method of surface abrasion, thousands of steel shot particles are propelled at the surface, which removes the top layers as well as any other contaminants
scabble your concrete floor A scabbler will leave a roughened surface behind, this can be ideal for some types of surface coatings. A chip-deck scabbler can remove up to 6mm of concrete in a single pass. While a scabbler is an effective method of surface preparation, it also poses a high risk of surface damage.
scarify your concrete floor  Scarifying machines consist of tungsten wheels, which work abrasively to level out a surface and remove contaminants. The operator has control over the depth of cut, as well as the finish of the surface. A finished floor can be left clean, roughened or textured.
chisel scrape your concrete floor Chisel Scalers are also known as tile lifters use rapid hammering actions to remove tiles and other surface contaminants. A range of accessories can be fitted to remove tile, grout, ice, fiberglass, concrete, asphalt, roofing shingles, or hardened deposits. Ride-on scrapers and and engine powered models are available for large scale works.