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TVM 11-03-2008 11:18 AM

Sealing grout for outdoor granite sidewalk
I live in southern CT (i.e., hot summers and relatively cold winters). Previous owners of our house installed a granite sidewalk ("rough" side facing upwards). In the span of < 6 years since the house was built much of the grout between the granite tile and the surrounding border of Belgian blocks has became brittle and cracked, with chunks missing altogether. I have largely removed the broken grout and replaced it with grout into which was mixed a kind of polymer solution that apparently strenghtens the grout. I'm told, however, I should also seal the grout. While this is probably straight-forward, I am confused by a few things, namely:

- do I seal just the grout or also the granite "tiles"
- if I seal both, do I use the same sealant?
- much of what I read about sealer appears to pertain to preventing staining, etc. I am less concerned about that than I am about resisting water infiltration and thereby future cracking. Is sealer sealer or is there a special outdoor sealer I should use?
- one person told me to use a "piping bag" to apply the sealer, which presumably implies the sealer is "thick"; what I've found at my local, less-than-helpful Home Depot is rather non-viscous liquid that the directions indicates should simply be sponged on (again, on the grout only or the granite too??). Would I just use a paint-brush to cover the grout itself?

Any advice (and suggestion for a particular product to use) would be greatly appreciated.

Bud Cline 11-03-2008 12:59 PM

I'm afraid you are misunderstanding the purpose of a grout sealer. Grout sealers are to protect from staining, nothing else. Grout sealers will not seal grout from moisture. Grout sealers are vapor transmissive. Your problem with your grout is movement not moisture migration. Movement is something that you can not control in a case such as this. Once you have added a chemical product when mixing the grout it will help to reinforce the grout while at the same time makes the grout impervious to any additional penetrating sealers in most cases. Repeatedly applying enough sealer will produce a topical coating for a time but will not stop moisture migration along the side of the stone. That juncture will naturally crack and allow moisture to penetrate the crack. Typically granite doesn't require a sealer.

The use of a piping bag to apply sealer is a mis-call by someone that must not know what grout sealer is, it can not be done.

There are many grout sealers that can be used for exterior use and they are freeze/thaw stable but they will only enhance and maintain the grout color and make cleaning a little easier, they WILL NOT reinforce the grout.:)

TVM 11-03-2008 02:07 PM

Thank you, Bud. This confirms my suspicions that sealer would not do anything useful in this case (I am not concerned at all about discoloration - in fact, I am hoping the new grout fades to match the pre-existing grout).

I've two additional questions perhaps you can answer. First, the new grout has, in places, developed a white film that I suspect has to do with the liquid polymer I was directed to mix into the grout. Once the grout has cured for a few days, would you imagine I could power-wash this away?

Second, in some places I did not thoroughly wipe-off the grout from the tile surface, and so there's a few remaining patches of thin grout on the tile. The same person who advised me to "pipe" the sealer suggested using a wire-brush to remove the film. Should I? Or would you imagine it will just flake away on its own over time?

I literally owe you thanks, for this means I can return $100 worth of sealer to Home Depot! Cheers - Tim

Bud Cline 11-03-2008 04:08 PM


...the new grout has, in places, developed a white film that I suspect has to do with the liquid polymer...
This may well be the case...but I doubt it. Those liquid polymers are designed to be mixed with such products. I suppose if it rained or the lawn sprinklers came on before the grout had cured a white (something) could develop.

I would more lean to "efflorescence". Basically efflorescence is the blooming of natural-salts that are contained in Portland cement products. Under the right conditions efflorescence will bloom with the introduction of moisture. Thus proving my statement that grout sealers (and additives) really don't seal anything in that respect.

If this (white) condition is efflorescence it will one day "play-out" as the salts are used up as a fuel for the blooming process. Efflorescence can be removed (however temporarily) by washing with white vinegar or any basic mild acid, but, the condition may return repeatedly for a time.Power washing will also likely remove the white but will eat-away at the grout particles also.:)


remaining patches of thin grout on the tile
Rubbing with a wire brush may damage the stone and leave black marks that won't easily be removed, I wouldn't wire brush the smudges. You can however also use the white vinegar and a softer plastic brush to remove the grout smudges. Again, any mild acid will do the trick. If white vinegar doesn't work fast enough for you you can buy sulfamic acid at most any home center in their tile department. Mix the crystals with water as directed and go for it again using a brush that is not metal.:)

Keep in mind that these acids can also damage the stone so don't get too aggressive and don't make a habit out of using any acid on natural stone.

Good Luck!!!:thumbup:

TVM 11-04-2008 09:47 AM

Thank you again
Thank you again, Bud - I only wish someone like you could be found at the local home centers!

Many thanks again.


Bud Cline 11-04-2008 10:19 AM


I only wish someone like you could be found at the local home centers!
Never gonna happen!!!

One of the major chains was approached by a recognized industry teaching entity about offering ongoing (on-the-road) teaching of big box employees and the chain refused. Turn-over is much too high and they really don't care about project outcomes, they only care about sales of course.:)

yesitsconcrete 11-05-2008 06:41 AM

as often as i have to pick up mtls in an apron store, 1/2 the time i hear absolutely incorrect advice being given,,, the 1 exception is a rtd electrician who manages the elec supply dept altho this example is anecdotal only,,, some of those guys don't even know water runs downhill.

whenever we laid flagstone or granite in farmington, grout/mortar was never used in exterior applications.

ccarlisle 11-06-2008 07:47 AM

A key point to this situation, apart from ground heaving due to the winters you have in CT, is the efflorescence; I would also tend to agree that's what you have, seeing that you have an outdoor stone installation with grout and whitish stuff appearing through the grout. What we haven't told you is that efflorescence may or may not be a permanent, recurring event.

It may also be temporary, but my money's on it being a continuous occurance, perhaps moreso after rain - but it'll be back. The moisture may be coming from the soil, through the grout. Hydrostatic pressure they call it...but given that is can come back, you can remove it without too much fuss. Eventually, it will weaken the grout and the grout fails.

A lot of variables there so I can't make a blanket statement, but in general, outdoor stone projects carry with them a number of variables not seen indoors. And whereas there are some stones than can benefit from sealing indoors, the same cannot be said of outdoor jobs.

IMO, there is little reason to seal granite stone sidewalks outdoors in order to prevent efflorescence - or almost for any reason - unless you are aware that every few years you'll have problems you would not have encountered without sealers. If you're OK with that, then seal away. But what are you trying to seal from? Ketchup stains? on granite? on a sidewalk? :no:

And, for worry-free NEW installations, either do not seal, or consider not using grout at all. That's a time-tested solution for ya!

detroitMi 11-09-2008 03:35 AM

The grout keeps craking while walking on it .you should use some caulk same color as the grout is,that might help

TVM 02-16-2009 10:43 AM

Grout/granite problems resurface
Folks - thank you for your input again about the grout and whether or not to seal it. I've a new question/problem for which I am asking - begging, actually - for you input again.

Having replaced the grout between the granite slabs on the sidewalk this past October, I was disappointed (to say the least) when I discovered this past weekend that much of the new grout had failed. (I should note that when I installed the grout, I first chipped out as much of the original broken grout as I could but I did have to marry-up new grout to old - perhaps that alone caused some problems). Here's a desciption of what I observed this weekend:
- a number of the slabs have heaved up and loosened so that they rock back and forth (this had not happened before, even when the original grout between the slabs was broken, and in replacing the grout I had not moved the slabs and certainly didn't take any up.)
- some of the grout "lines" between the slabs, even though it did not break, have separated from the edge of the slabs, leaving a gap.
- the worst cracking took place in the grout between the outside edge of the slabs and the belgian blocks that line the sidewalk (this I probably could have anticipated since the space that needed to be spanned was as much as an inch, and the grout I used indicated that it was not intended for spaces above 1/2 inch, but the grout I used was the only type I could find at all).

So I am debating whether to try this again myself or bite the bullet and hire someone. If I attempt this again, here are my questions:

- do I need to chip out all the grout entirely and start over or could can new grout successfully meet up with old grout?
- is there a specific brand of grout anyone would recommend?
- is using a polymer "hardener" worthwhile (might this have contributed to the cracking?)
- could I use cement instead of grout? (Two years ago I used cement how hold in place beligian blocks that line a section of our driveway and there's been no problem with it)
- if I use cement, can I apply it the same way as grout, or should I take up all of the slabs, line the underside with a screening of gravel topped with cement and then set the slabs into the cement?

I am sorry to ask what I am sure seem like amateur questions to you, but an amateur is what I am!!

Thank you!!

yesitsconcrete 02-16-2009 10:57 AM

you guys answer,,, i already said my piece :(

TVM 02-16-2009 11:03 AM

I guess that means my question(s) was (were) stupid. I am at a loss as to what I should do. You said in your post that in Farmington you didn't use grout/mortar. What did you use? Just sand swept into the spaces? Can sand span spaces that are 1/2-1 inch wide?

You can see I am not embarrassed to express my ignorance. As Denzel Washington's character says in the movie Philadephia, explain this to my like I am 6 years old!!

yesitsconcrete 02-16-2009 11:39 AM

yep, sand,,, when you've got freeze/thaw as in ct, replacing the mortar's just recreating the existing problem imn-s-hfo,,, now go to work ! ! !,,, we're all ignorant about something - me, usually, more'n most others :whistling2:

TVM 02-16-2009 11:58 AM

A few "last" questions ...
... okay, probably not my last but my last for the moment anyway.

1. The sidewalk ends with a 4" drop-off to the driveway. The final slap of granite is about 4' long, 8" wide. It sits on top of 1/2 buried belgian blocks but has about a 2" lip. Right now, this is grouted in place (and the grout, while spanning in places as much as 3," is not yet badly cracked but is cracking). The slab would not be held in place by sand since there's nothing to prevent it's movement towards the driveway. If I am otherwise filling spaces with sand, should I cement the underside of this slab to hold it in place (i.e., cement instead of grout?)

2. To help with drainage and heaving, here's my thought: dig down another 1-2 inches, line with crushed stone, then cover with landscape fabric and sand (into which obviously I set the slabs). Is this correct thinking on my part?

3. The one time I did help with dry construction of a patio, we kept the spacing between the bricks very small. Can sand actually span the 1/2 space between these granite slabs and the (in places) 2"+ span between the outside edge of the slabs and the belgian blocks that line the sidewalk firmly enough not to have the slabs move too much/too often?

Thank you again! Your patience is appreciated as equally as your information!

ccarlisle 02-16-2009 12:02 PM

All of us have alluded to an unstable structure caused by movement, in turn caused by freeze/thaw...that's where any extra effort should be put: solving that. Don't bother regrouting. You'll be doing it all again in 6 months.

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