Grinding the floor--what about stemwall and corners?

[zephyr9900]

Hi all! My first post here. Thanks to all who participate in this forum, which has greatly helped in my own project to this point.

My wife and I recently bought a house with a "2-1/2 car" garage--two actual stalls with individual doors and a raised area to the side that is as wide as a stall itself (i.e. my new workshop!) There is also a 2-1/2 foot wide ledge along the back wall.

The garage is about 600 square feet, and I have ordered two kits of EpoxyMaster through Costco. Unfortunately, the floor had been sealed, so I rented a hand grinder (and bought a 7" diamond cup wheel...) last weekend. Four hours later I had about half the floor ground. I am renting the grinder for another half day tomorrow to finish the grinding. I've removed the baseboards and door thresholds in order to get right up to the edges of the floor.

On the broad surfaces the grinder is doing a good job. However, in each interior corner there is a triangle about 4" on a side where the wheel can't reach, in areas along the ledge the concrete dips (see the third picture) and there is the ledge itself and stemwall along one side to deal with. I haven't seen (maybe not searched hard enough) those issues mentioned.

Is wire-brushing the "inaccessible" surfaces sufficient, or should I plan to acid-etch them before the final washing of the floor?

Thanks,

Randy

 

[haugy]

I wish I could find it. Someone recently did a floor that had this exact setup. It had a small step up section like yours. I can't remember what they did.

Maybe someone else remembers.

Other than that, I'm not sure if the wire wheel will do enough. If it's a solid enough one maybe. I've seen wire wheels do some damage to concrete when still spinning from use. I would imagine if you get a good enough one, and take your time it would. But that's a complete guess.

 

[BigEd]

We used a belt sander to get into the spots the wheel couldn't reach.

 

[Jeremy W]

a local rental place where I live had a grinder made for corners I could rent, not sure what it was called but they said it would work.. Might check with rental places in your area.

 

[drsifu]

looks like you did a great job with the grinding.

because of its location, I personally would not worry too much about it. but if you are hell bent on prepping those areas, acid-etch it.

 

[zephyr9900]

A belated thanks for the answers, guys. I did end up etching the vertical surfaces with the etchant that came in the EpoxyMaster kits (well, the etchant from one of the two kits) and scrubbing with a stainless-steel wire brush (hand brush--all my equipment is still in storage in California...) while the concrete was still wet.

I finished the grinding on Saturday. Renting the grinder for only half a day was way optimistic. I took over 5 hours to do the remaining floor.

Thank you for the compliment, drsifu. It looked really nice until I hosed it off after etching the vertical surfaces, which washed all the packed-in grinding dust out of all the cracks... Filling the cracks will be tonight, using a kit of EpoxyShield Concrete Patch. None of the cracks (other than a couple of wide spots) is larger than 1/8 x 1/8 or so, so the patching should go quickly.

For the 3 +/- stall garage floor I went through 3 sets of replacement dust filters for my half mask, 4 primary fine-particle filters and 8 fine dust bags for the shop vac. Lots of dust, but I live in a cul-de-sac and wanted to keep it contained as much as possible.

Randy

 

[st_sdoyle]

another option for those corners is to us Behr Concrete & Masonry Paint Stipper. It gets epoxy, sealer and some other stuff off concrete. You paint this stuff on, and about 30-45 minutes later (after it gets into the concrete and loosens the sealer) you can spray it off with a high pressure washer. My 1200psi did the job, but I went and rented a 3000psi and did the whole garage in a day! I did not want to grind the floor. New epoxy floor holding up very well!