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Because of effloresence appearing on my porcelain tiled deck after rain events, I am planning to replace the existing grout with epoxy grout which will create a waterproof barrier. But I first need to remove the existing grout joints, which are < 1/8" width. It's my understanding that porcelain tiles can be susceptible to chipping so I'm not certain which method would be most appropriate to perform this work. I was considering using a grout blade on my oscillating tool, but I wanted to get some feedback before proceeding. enter image description here

  • I'm not clear on 'rain events'... is it that rain gets on your tiles from the top and you don't like it? Or is it coming from below? Either way, you might consider just sealing the tile/grout and not causing yourself the agony of removal (and applying epoxy grout -- that stuff is terrible, imho!) – Aloysius Defenestrate Jul 8 '18 at 19:19
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    Utility knife and extreme caution. Those "grout removal saws" are too thick and will be more likely to rub against the edge of the tile, risking glaze chips. – Jimmy Fix-it Jul 8 '18 at 20:11
  • When I state "rain events", I'm referring to water that penetrates through the grout joints when it is raining. The efflorescence is occurring when the water is pulled back to the surface during evaporation that's leaving dissolved minerals from the thinset onto the surface. Interestingly, the tile layer claims to have used a latex thinset that should not have caused efflorescence. However, I've removed the efflorescence by scrubbing with a sulfamic acid solution. – Grant Jul 8 '18 at 20:23
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    I see... in that case, I'd suggest you reapply a grout sealer (maybe 2 coats) and see how it goes. If not satisfactory, @JimmyFix-it is right. – Aloysius Defenestrate Jul 8 '18 at 21:50
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There is a Dremel Grout removal attachment, which consists of a fixture to hold the tool at a 45 degree angle, and you can get a 1/16 inch carbide cutter bit.

I've used this setup several times to remove grout for renewal or tile replacement. It can work quite well if the grout is really a sixteenth wide. Its not easy, but you can chip the tiles if you're not careful. I inevitably break the bit, and will always buy at least two.

https://www.dremel.com/en_US/products/-/show-product/accessories/568-grout-removal-attachment

  • Although the overall grout joint spacing is ~1/8", there are many joints that are slightly <1/8". Hence, I will need to limit the blade to 1/16" thickness to be safe. I have a Bosch oscillating tool and have used a grout grinding blade in the past for removal of wider joint thickness (1/4" - 1/2") and has worked great! Dremel has a blade that's 1/16" thick that I could use with my Bosch. Unfortunately, the Dremel Grout removal attachment isn't compatible with the Bosch! images-na.ssl-images-amazon.com/images/I/41mVBfx6ZxL.jpg – Grant Jul 9 '18 at 15:09
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You will run the least amount of risk of chipping the tile if you do the job with hand tools. Use a 1/16” carbide grout saw, and you don’t need to remove all of the grout to the bottom of the tile, just more than 1/16”. Pulling the tool is safer for the tile than pushing it.

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