It keeps coming back, now to end this tile menace.
May 27, 2012 10:58 PM Subscribe
What is this weird stuff that appears to be growing in grouted areas of my outdoor patio tile? Photos inside.
OK, after a major spring cleaning scrubdown on the outdoor patio, this appeared in the space between tiles on part of the deck. It does not appear in places that get direct sunlight. It feels a bit crumbly and hard, like a salt buildup (easy to remove an crumble with fingers). The patio was scrubbed down using dish soap (only thing available at the time) and the buildup reminds me of what I used to see in my really old house in the basement where salts leached into the foundation and accumulated on the inside wall -- I thought it might be an interaction between the soap and something in the grout.
Photo A, B. Is this something I need to repair, or kill? Thanks.
OK, after a major spring cleaning scrubdown on the outdoor patio, this appeared in the space between tiles on part of the deck. It does not appear in places that get direct sunlight. It feels a bit crumbly and hard, like a salt buildup (easy to remove an crumble with fingers). The patio was scrubbed down using dish soap (only thing available at the time) and the buildup reminds me of what I used to see in my really old house in the basement where salts leached into the foundation and accumulated on the inside wall -- I thought it might be an interaction between the soap and something in the grout.
Photo A, B. Is this something I need to repair, or kill? Thanks.
Best answer: It's probably efflorescence. It's common in concrete. From your picture, I'd guess calcium sulphate crystals.
posted by RichardP at 11:25 PM on May 27, 2012
posted by RichardP at 11:25 PM on May 27, 2012
Yeah, it's almost certainly efflorescence. No need to worry and it will just wash/brush off. I think that some dish soaps have salt in them, which may have triggered this.
posted by dg at 11:34 PM on May 27, 2012
posted by dg at 11:34 PM on May 27, 2012
I think that some dish soaps have salt in them, which may have triggered this.
I guess that's possible, but efflorescence is an incredibly common thing in masonry and concrete, without the presence of any kind of soap.
posted by LionIndex at 11:56 PM on May 27, 2012
I guess that's possible, but efflorescence is an incredibly common thing in masonry and concrete, without the presence of any kind of soap.
posted by LionIndex at 11:56 PM on May 27, 2012
I also believe it's efflorescence - this happens where the tile meets the water in our concrete swimming pool. The pool man uses muriatic acid to fight it, but that is some seriously nasty stuff.
You might want to select a small test area, clean it with vinegar and a stiff bristle brush, and then seal the cracks with grout sealant. It probably won't stop it, but it will slow it down.
Our hardware store also stocks latex-based sanded grouts that seem to keep the crystals to a minimum, but that's a whole nother project.
posted by halfbuckaroo at 5:14 AM on May 28, 2012
You might want to select a small test area, clean it with vinegar and a stiff bristle brush, and then seal the cracks with grout sealant. It probably won't stop it, but it will slow it down.
Our hardware store also stocks latex-based sanded grouts that seem to keep the crystals to a minimum, but that's a whole nother project.
posted by halfbuckaroo at 5:14 AM on May 28, 2012
Best answer: It has nothing to do with the soap. Soap salts are slimy---this is what soap scum is. Left for a while, soap salts will turn pink/red with bacterial action.
As other have said, this is efflorescence. It's typically cause by groundwater upwelling through the concrete, carrying salts from the concrete then drying on the surface. It feels like salt crystals because the residues are very similar chemically to table salt.
It's not a functional concern, particularly on non-structural masonry like a patio. A mild acid will redissolve it. A vinegar solution is what I'd try. Muriatic acid will work, but it's overkill IMO.
The way to resolve it long-term is to improve the drainage under the pavers, adding a gravel layer or other drainage systems. If it's not causing structural issues with your house, I wouldn't worry about it.
posted by bonehead at 11:01 AM on May 28, 2012
As other have said, this is efflorescence. It's typically cause by groundwater upwelling through the concrete, carrying salts from the concrete then drying on the surface. It feels like salt crystals because the residues are very similar chemically to table salt.
It's not a functional concern, particularly on non-structural masonry like a patio. A mild acid will redissolve it. A vinegar solution is what I'd try. Muriatic acid will work, but it's overkill IMO.
The way to resolve it long-term is to improve the drainage under the pavers, adding a gravel layer or other drainage systems. If it's not causing structural issues with your house, I wouldn't worry about it.
posted by bonehead at 11:01 AM on May 28, 2012
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posted by Kid Charlemagne at 11:02 PM on May 27, 2012