# Sealing Grout



## Nestor_Kelebay (Jun 17, 2008)

There are two kinds of grout; epoxy grout and cement based grouts.

Epoxy grouts are impermeable, so they don't need to be sealed.

Cement based grouts dry porous and do need to be sealed. If you don't seal your grout in a shower, mold and mildew will begin to grow on (and actually inside) the porous surface of the grout.

However, in order for any grout sealer to work best, you need as much of it as possible to be absorbed into the grout, and you need it to be absorbed as deeply as possible as well, and that means your grout needs to be as dry as possible when you seal it.

Your grout is wet all the way through, so you need to leave it to dry as long as possible. The instructions on the grout seal should give you some guideline as to how long to leave it. On the grout sealer I use, it says 10 days, but the dryer the grout is, the more sealer will be wicked into it when you seal.

Is there another shower in your house you can use while this grout is drying? Can you cover the bottom row of tiles with wax paper or plastic or something and have baths instead for a while. (You'll need to pull off some of the tape to expose that covered tiling when the tub isn't in use.)

PS:
You don't need to know the rest, but you'll be a better person for it if you do.

Your tiling contractor is kinda telling a half truth when he says you don't need to seal your grout. To be correct, what he should say is that you don't need to seal it right away, perhaps even for up to a year, maybe.

You see, all "cement" based products, like concrete, brick mortar and tile grouts contain portland cement, and portland cement is made by heating limestone to convert it into something called "quicklime" or calcium oxide or CaO. When they make portand cement, they also add clay, which contains silicates (SiO2) and the result is that you get different kinds of calcium silicates formed, like 2CaOSiO2 and 3CaOSiO2.

http://en.wikipedia.org/wiki/Portland_cement

When you mix those calcium silicates with water, the quicklime, CaO, in the cement is converted to hydrated lime, Ca(OH)2, and it's those hydroxyl (-OH) groups on the hydrated lime that make the cement highly alkaline. That high alkalinity will prevent mildew from growing on the grout.

However, CO2 from the air gradually reacts with the hydrated lime in the cement (now grout) and the hydrated lime is gradually converted into calcium carbonate, CaCO3, which is the primary ingredient of limestone, which is the stuff we used to make portland cement from in the first place.

http://www.graymont.com/what_is_lime.shtml

That cycle, from CaO to Ca(OH)2 to CaCO3 and back to CaO is called the "lime cycle", and it's the reason why you don't need to seal your grout right away.

For the next few months (at least) mildew won't grow on your grout because it's too highly alkaline. As the CO2 in the air reacts with the hydrated lime, Ca(OH)2, in your grout to produce limestone and a H2O molecule (which float away), your grout becomes less and less alkaline and more and more susceptible to mildew growing on and in it.

So, "not needing to seal" should be read as "not needing to do it right away".


----------



## AtlanticWBConst. (May 12, 2006)

qvminich said:


> Do we need to seal the grout in our newly tiled shower? The tiler says no and my husband says yes. I remembered sealing the grout in our living room when we removed the carpet and switched to tiles. Unless the newest grout on the market has changed and is now 100% waterproof.
> 
> I have now included pictures of my shower ceiling for those who were waiting to see them before assisting me further with our "shower ceiling".
> Thanks.
> ...


Probably the reason for two different answers:

Do you "need" to use a grout sealer? No
"Should" you use a grout sealer? Yes.

Your experience with sealing your flooring tile/grout:
Sealing tile and grout installed on floors is always a good practice, to protect dirt from penetrating the grout and staining it. Also good to seal the tiles, as these too can stain, dependant on the kind of tile and the tile material.

Suggestion:
I'd suggest that you use an appropriate "premium" brand of grout sealer, to inhibit mold and mildew growth. Allow approximately two weeks, or grout manufacturer stipulated time frame, before applying the grout sealer to the grout. This allows the grout to fully cure, prior to sealing it. Also, follow the manufacture's instructions for application and clean-up.

Which brand/kind of sealer?:
See a reputable tile supplier (NOT, a Big Home Improvement Store Person) and ask them which one is best suited for the kind of tile you installed, the kind of grout you used, and the environment they will be in (shower).

Best of Luck.


----------



## buletbob (May 9, 2008)

all the above! its up to you.


----------



## qvminich (Aug 19, 2008)

*grout*

Thank you all for your replies, especially Nestor for all that detail which is right up my alley as I'm a very detailed oriented gal. The new shower is in our basement so we can let it sit all we want and dry up before we seal it which is what we will do. I'll read the box to see how long it should sit because the contractor left all the leftovers. 

I woluld be very appreciative if any of you folks could help me with my shower ceiling dilemma in a different post. Thanks a bunch and a good evening to you all.

QV


----------

