Grinding/Sanding Down SikaFlex Control Joints

navin · Aug 4, 2015

Hi all -- finally getting around to my garage refurb project (2nd times a charm hopefully). I just filled the joints in my garage with SikaFlex SL from Home Depot and was wondering if I should be able to use a floor screener over the joints?

I need to rough up the previous epoxy coating in preperation for a new coating and just wanted to make sure what to do with the filled expansion joints now.

Thanks!

Shea · Aug 5, 2015

Hi Navin. It would have been best to fill the joints after the new coating. SikaFlex does not sand well nor does it accept a coating. You can't really cover them with anything as the sanding screen will tear it up. You can either sand up to the joint or remove the SikaFlex and refill after you are done. Are they filled level to the floor or a little lower?

navin · Aug 5, 2015

Shea,

Thanks for the reply, looks like I might have jumped the gun on this one. The joints are filled level to the floor at the moment, but I did have some extra material run out of the joint so was hoping that either the sanding screen or something would flatten it out.

I was kind of following this guy's thread on using SikaFlex and then Epoxy: http://www.garagejournal.com/forum/showthread.php?t=89673

Maybe I should just remove it and pick up a gel crack filler...

Garage Flooring · Aug 5, 2015

What about cutting it with a razor like you would a gel joint filler?

Shea · Aug 5, 2015

I just reviewed the thread Navin. It looks like he prepped the floor first then filled the joints. After that it would just require taping the joint until after the epoxy was applied.

I just realized that you are applying over a previous coating. If that is the case, I would tape up the joints and then use a block sander or pole sander with 100 grit paper on the edges near the tape. You are just roughing up the surface, not removing the old coating (unless it failed and is peeling up). That should give you a buffer area to run the sanding screen up close but not over the joint.

What about cutting it with a razor like you would a gel joint filler?

It's hard to cut a clean line with SikaFlex because it tends to get squirmy. The blade has to be real sharp and changed frequently. It can be done but it loses that nice clean look.

navin · Aug 5, 2015

Hi Shea -- that's correct, but I just re-read a post about filling expansion joints on either your site or Justin's and realized that using SikaFlex isn't going to give me the "seamless" look.

So looks like I'll be pulling up the SikaFlex (hopefully wont be too bad as it's only been in the joints for about a day now), and then use a gel crack joint filler and grind that smooth.

navin · Aug 5, 2015

Also -- what would you guys reccomend for a expansion joint filler if I want that seamless look. The legacy stuff looks awesome, but seems like it would be a pain in the *** to the get inside the crack and spread evenly.

I forget which site it was, but they reccomended this product: http://www.amazon.com/dp/B008VDHY48/?tag=atomicindus08-20

Seems like it would be easier as I can just pour it in, just want to make sure I'll be able to grind it to smooth unlike the SikaFlex.

davidlee · Aug 5, 2015

I don't want to disagree with the pros here but I used SikaFlex on a cold joint approx. 40 ft long. I slightly overfilled the joint, ground it down with my Dimabrush and then coated the entire floor with Rust Bullet and flakes. You can't see the joint now and the Rust Bullet has adhered to it with no problems so far. The RB has been down at least 3 months now.

Garage Flooring · Aug 5, 2015

davidlee said:
I don't want to disagree with the pros here but I used SikaFlex on a cold joint approx. 40 ft long. I slightly overfilled the joint, ground it down with my Dimabrush and then coated the entire floor with Rust Bullet and flakes. You can't see the joint now and the Rust Bullet has adhered to it with no problems so far. The RB has been down at least 3 months now.

Which one of their products did you end up with?

davidlee · Aug 5, 2015

I don't remember the name but it was in a calk tube and I got it at HD. It was a self level product. It did not harden but ground off smoothly with the Dimabrush. I also used it the same way in a number of hairline cracks with the same results.

navin · Aug 6, 2015

I pulled most of the SikaFlex out last night... looking over my floor, it's a nightmare... I'm leaning towards those Excelia tiles again.

Shea · Aug 6, 2015

Yes, the toughest part about putting down a quality coating is the floor prep. Just keep in mind that once the prep work is done, the actual application is easy compared to the rest.

navin · Aug 6, 2015

I thought it wouldn't be too bad since the old epoxy coating hasn't lifted/peeled etc... but then there is this:

Which supposedly is from sort of contaminiation in the concrete [tire dressing, etc]. When I first put the epoxy down I only acid-etched. So now my main concern would be how I go about addressing the problem spot above if I were to redo the epoxy top coat.

NitroShark · Aug 6, 2015

You would grind it,

Then test it by sprinkle a small amount of water over it. Should take just a few minutes to completely soak in.

Most likely you have or had silicone (or similar material) in that area.

Shawn

navin · Aug 7, 2015

Wouldn't the silicone or whatever contaminant have sunk it pretty deep into the concrete... wasn't sure if a grind would be sufficent.

navin · Aug 10, 2015

Wanted to bump this up -- just to see if anyone else has opinions on how to fix the previously contaminated areas of the garage (see picture above). Will a grind and recoat fix this?

12ozd · Aug 10, 2015

I would grind it, apply primer, apply finish coat.

navin · Aug 10, 2015

Grind, as in... remove existing coating (dimabrush coating removal tool), or use the Concrete prep tool?

Shea · Aug 10, 2015

Hi Navin. You need to use the removal tool for sure. What type of epoxy did you originally put down? It looks like a higher solids epoxy. If that is the case, we recommend renting an Edco 10" single head concrete grinder from Home Depot instead. It will get through the coating faster and will actually remove more concrete than what the Diamabrush will.

The Diamabrush is a great grinding tool for most situations but it does have its limitations. In your particular case you need will most likely need to remove some of the surface of the concrete in that area in order to rid it of the contaminant, depending on how deep it penetrated. The Diamabrush is good for removing low solids coatings and paint, but it can be slow work for a higher solids coating. Plus, it will not remove nearly as much concrete as the Edco can. It's designed more for prepping the concrete than removing layers.

Once you do grind the area you will want to conduct a water test to see how it is absorbed. One thing to keep in mind is that there are other primers available such as oil stop primers that can help with contaminants.

navin · Aug 10, 2015

Shea,

Thanks again for the insight. I wasn't aware that the Home Depot's carried the Edco grinders. The epoxy coating that is down right is Epoxy-Coat (so 100% solids).

Grinding/Sanding Down SikaFlex Control Joints

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