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DIY bathroom glassblock window advice

  1. Nov 24, 2016 #1
    I have a glass block window in my shower. It's about 25 years old. Because it's in the shower the water directly hits it. Over time the sanded grout is starting to erode. It's not super bad, but it's to the point where I think I should patch it. The question is whether to fill in and cover with clear silicone caulk or patch with fresh sanded grout. Any thoughts?
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  3. Nov 24, 2016 #2


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    I've asked a pro.
    It depends on the width of the joint. Above 8 mm it's better to use sand grout, and otherwise silicon could be used. I guess silicon will split too soon on broad joints. In any case it should be dry and free of oil (but that's clear anyway).
  4. Nov 24, 2016 #3
    It's a little more than 1/4in. Sounds like silicone could be ok.
  5. Nov 24, 2016 #4


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    Well, the one I've asked is probably a little bit biased towards silicon. But if you close the tube properly, you can keep it for further use.
    And for the solution with sand grout you'll have to steal it somewhere, because it makes no sense to buy it - at least if the are sold in the same bulks as here. Only prepare a very wet piece of rag (?) to smooth the joint afterwards.
  6. Nov 24, 2016 #5

    Stephen Tashi

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    There are modern types of grout that aren't called "sanded" or "unsanded". I think they have plastic fibers in them. The ordinary type of sanded grout should be sealed after it is installed. You can buy "addtive" to mix it with that makes the grout more durable - and perhaps makes the sealing step unnecessary.

    If you're talking about clear silicone general purpose caulk, in places where I've used clear caulk, it gets very nasty looking over time. A shower might be an exception to that rule.
  7. Nov 24, 2016 #6


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    I have used a silicon sealer with sand embedded in it for the tiles on our bathroom floor. It has worked well. Some silicons (not for aquariums) have fungicides to suppress mold.

    Silicon can be messy to use. I recently heard (from several aquarium keeping friends) but have not yet tested that you can use plastic grocery bags (or saran wrap) for wipe it up. It is supposed to work well. Normally it would be paper towels.

    The stores in my area also have small amounts of grout available in small tubs (like pint or quart {~1-2 liters} sizes), so you might not have to get large amounts.

    There are also special dremel bits for removing grout from between tiles.
  8. Nov 24, 2016 #7


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    I've used silicone to seal around a shower and had problems with mould/ mildew. So if I didn't need flexibility I'd stick with mineral grout.

    I have heard recently that neutral cure silicone is better than the acid cure silicone that I've used before. So I'm trying again with that, but it has only been in for a month or two. I won't know how it compares long term for at least a year or two.
  9. Nov 25, 2016 #8


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    I recently renovated a whole bathroom, and used epoxy grout. Vastly superior to ordinary grout, though trickier to apply (and more expensive).

    Where glass meets tile (e.g., my unframed glass showerscreen) a neutral cure silicone is best. Such silicones have better adhesion and weatherproofing properties compared to acetoxy (vinegar-smell) silicones -- making them a superior option for wet area applications.

    You might also find Renovate Forums a useful resource for this sort of thing. Lots of experts there.
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