Is grout waterproof ?

In a typical tiled shower installation, is the grout waterproof so that it keeps water out of the lower layers?
Is sealing necessary to make it waterproof? Or does sealing just keep the dirt out of the grout and it is just as waterproof sealed or not?
Thanks,
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- Bob - wrote:

No cementatious material is waterproof. That includes grout.
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dadiOH
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- Bob - wrote:

Almost all grouts (some epoxy grouts are an exception) are somewhat permeable to water, in any case there are will likely be mechanical imperfections in the grout, increasing over time, which will admit water by capillary action
Generally tiled bath and tub walls are installed to a rigid backing material highly resistant to water damage ("Durock" is a common example) with a vapor barrier behind that, if a tub or shower floor is tiled it's generally installed over a (hopefully) watertight assembly called a "pan", which usually incorporates a waterproof "liner".
See for example:
http://www.tileshop.com/diy/showerbase.pdf
Michael Thomas Paragon Home Inspection, LLC Chicago IL mdtATparagoninspectsDOTcom
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On 9 Jul 2006 11:12:48 -0700, "MDT at Paragon Home Inspections, LLC"

OK... lets move on then....
Are there any products that could be used to waterproof or water resist older grout ? This particular shower not built over any sort of cement board. it looks like some sort of plaster board with paper covering of some sort. Not standard sheetrock but not much more appropriate I don't think. ... this is from the 70's so who knows.
It is in good shape and the deteriorated areas that I repaired were over the edge of the fiberglass pan so they are not an issue. However, I am concerned that what I found under there was not a proper surface and that if the grout wicks water it will eventually destroy the rest of the unit.
Anything that can be done preventively to prolong the life a few years?
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- Bob - wrote:

A sealer, Bob.
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dadiOH
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responding to http://www.homeownershub.com/maintenance/Is-grout-waterproof-126470-.htm Nestor Kelebay wrote: Bob: Grout will prevnt liquid water from passing through the tiling. However, it won't prevent humidity from passing through. As the humidity increases inside the wall, condensation can occur to form liquid water.
What you want to do is seal your grout with an ACRYLIC film forming grout sealer. If you see the word "siloxane" on any bottle of grout sealer, don't buy that grout sealer. Siloxane means a silicone based plastic, and all silicone based materials seem to have the same problem; nothing sticks well to them. The problem with using a grout sealer made from a silicone based plastic is that you can't add more sealer a few years down the road to build the protection back up to former levels. That's because the new grout sealer simply won't stick well to the old grout sealer, and will flake and peel off.
You're much better off with an acrylic film forming grout sealer which doesn't have that problem.
Do a Google search for DuPont Stone Tech products. I don't know if DuPont makes a film forming acrylic grout sealer, but if they do, I'd bet it's a good quality product. If you can get DuPont Stone Tech's 1-800 Customer Service phone number, you can just ask if any of their grout sealers are acrylic and form a film rather than get absorbed into the grout.
The grout sealer I use on all of my bathrooms is made by the Glaze 'N Seal company of California and called simply "Grout Sealer". I very much like this sealer as it is very strong and lasts a very long time. I imported 4 quart size jugs of it from California into Canada.
If you don't know what else to get, you can always use Tile Lab's "Gloss Sealer and Finish" or "Matte Sealer and Finish" available at Home Depot. Both products use the same acrylic binder, but the Matte has extender pigments inside it that cause it to dry to a flat gloss rather than a high gloss. One thing I like about these two products is that Tile Lab also makes a very effective remover to remove the grout sealer should you ever need/want to. Tile Lab's "Heavy Duty Cleaner and Stripper" makes light work of removing either Gloss or Matte grout sealer.
Hope this helps.

------------------------------------- ..in solidarity with the movement for change in Iran.
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Again, I swear by this stuff. What convinced me is the guy at the tile store. I had a tiled shower in one of the HUD Wrecks I bought. The grout was all faded bad. They were small tiles maybe 2"x2". I brought in a block in tact with grout that came off the lower wall.
Guy opens a bottle and puts it on the grout. It brought the color back like magic. Then on the edges you could see the stuff changing the grout all the way through it's depth. Penetration, not coating.
http://www.custombuildingproducts.com/ProductCatalog/aquamixproducts/Sealers/amisealers_enhancers/EnrichNSeal.aspx?user=arc&lang=en     -or- http://tinyurl.com/39nb85u
Before and after pic:
http://oi51.tinypic.com/21mx277.jpg
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