How do I fix up my garage floor so I can epoxy it?

[L-Plates]

I want to paint our garage floor with epoxy floor coating.  It's 20 years old and has its share of stains. It needs taking care of.

The concrete has a fair few hairline cracks running across the surface, and a few pits here and there.  It has also been producing some chalky residue (efflorescence) along some of the cracks.  The residue has only started appearing in the last couple of years (perhaps as the cracks appeared?)

What do I need to do to get the concrete floor ready to epoxy?

Thanks.

Community manager's note: Check out How to apply epoxy to a garage floor for expert advice.

CracksEfflorescencePitting

[MitchellMc]

Welcome to the Bunnings Workshop community @L-Plates. It's wonderful to have you join us, and many thanks for your question about preparing your floor for epoxy paint.

Here's our step-by-step guide: How to apply epoxy to a garage floor. In your case, you need to fill any cracks or damage before the paint application with Timbermate 500g Concremate Expanding Cement. After the filler has cured, you can sand it back and blend it into the surrounding concrete with a Trojan Concrete Rubbing Sharpening Stone.

Here's our Best Advice on How do you prepare a garage floor for painting?. You might also be interested in reading through @maknilsin's Epoxy garage floor project.

I'll include the Dymark instructional video below, which has a section on filling cracks.

Please let me know if you have any questions after reading the guide and watching the videos. 

Mitchell

[L-Plates]

Hi Mitchell, thanks for your advice.

Do I need to use something like Crommelin Efflorescence Remover before starting?

[EricL]

Hi @L-Plates

Using Crommelin Efflorescence Remover will surely help. It removes any salt deposits on your cement floor. It also acts as a general cleaner prior to paving or sealing. 

Please keep us updated with your progress, we look forward to seeing your garage floor sealed and ready for use.

If you need further assistance, please let us know.

Eric

[L-Plates]

Hi,

I tried the Crommelin Efflorescence Remover over the Christmas break but it didn't seem to do anything.  (The product reviews on the main Bunnings site aren't that encouraging either). The instructions says to use it diluted but, after a couple of goes with no result, I applied it undiluted (albeit to a wetted floor), but nothing seemed to change.  The concrete is still stained with the efflorescence patterns.  Maybe I am misunderstanding what it is doing?  Is it important to get rid of the efflorescence before patching and epoxying, or am I doing something that is not vital (and will eventually be covered by the epoxy)?

[EricL]

Hi @L-Plates

I'm sorry to hear that the Crommelin Efflorescence Remover did not remove the efflorescence from your cement floor. Efflorescence occurs when you have three factors present, a cracked cement floor, water, and carbon dioxide. Carbonation occurs when the lime in the cement reacts with the carbon dioxide in the air and water brings it up to the surface. If you have a water leak under the cement floor, the reaction will keep occurring. But if water is only being brought from the outside and settles in the cracks then the reaction should stop when your floor is sealed.

I suggest trying Glitz Green 2L Cleaning Vinegar in combination with a stiff brush. A mixture of 50/50 with water will give you a very strong solution. This is a very safe method of removing efflorescence. 

In conclusion, if there is no source of water under the cracked area of the concrete floor, sealing the floor will stop the efflorescence from occurring. But if water is finding a way to the cracked area, the seal will get pushed off by the calcium carbonate and the seal will fail.  

If you have any other questions, please don't hesitate to post them.

Eric