Best way to seal crack in concrete slab?

I have a very thin hairline crack in my conrete slab, right in the middle of the garage doorway. It is barely visible and is so thin I can't even feel it with my fingers. Unfortunately, water still finds it's way into the crack on the outside of the garage door and seeps along the crack to the inside of the garage. So, I would like to seal up the crack before it turns into a bigger issue.
Any recommendations?
Most crack sealers seem to be made for larger cracks, so I'm not sure they would even get down into my hairline crack.
Thanks,
Anthony Watson www.watsondiy.com www.mountainsoftware.com
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On Thursday, March 17, 2016 at 10:23:48 AM UTC-4, HerHusband wrote:

If it's really that thin I'd try filler superglue from the hobby store. There is gray caulk for concrete if you think it's a little bit more open and you can use a plastic squeegee to force it in the crack and bit like grouting tile.
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On 3/17/2016 7:20 AM, HerHusband wrote:

Is water getting *into* the crack or simply clinging to it as a "guide" to flow into the garage?
I.e., are you sure the crack is the cause and not just a *symptom* (of a low spot in the floor)?
As a first attempt, I'd try some silicone caulk applied with a trowel (or float). This will tell you if the crack *is* the "low spot" vs. just RESIDING in a low spot.
Once you know what the case is, you can peel the silicone off (or, scrub it off with a wire brush) -- it won't last applied as thinly as your description suggests it would be.
But, based on what this discloses, you might then be able to try an epoxy intended for use with concrete/cement applied using the same sort of technique. Make a serious effort to clean up the crack and surrounding areas before trying to apply it.
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On 17/03/2016 17:03, Don Y wrote:

I would chisel along the crack and make a V shaped channel, then wet it and sand and cement it.
--
Bod

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On 3/17/2016 10:12 AM, Bod wrote:

It's a "very thin hairline crack", "barely visible" and "so thin I can't even feel it with my fingers". No need to make a *bigger* problem out of it!
The crack may not *be* the problem but, rather, just a convenient place for water to adhere as it migrates inward. It could be a low spot in the slab (there is *some* reason for the crack being there!).
Instead of weakening that area (chiseling it out) and then trying to back fill, just try something that "flows well" (or, can be FORCED to "flow well") that also ADHERES well (cuz you won't have much "material" being added to that area if it is really as insignificant as Anthony's description suggests.
(A really loose slurry of mortar and water would "flake off" after drying)
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The crack extends from the edge of the slab on the outside of the door, to a point about two feet inside the garage. I haven't checked it with a straight edge, but there don't appear to be any low spots in the floor.
The slab is 6" thick, with an additional 8" thick reinforced footing under that front edge. Significant settling seems unlikely.
This is the only crack I have in the floor after 15 years, despite it being 24'x28' with no control joints anywhere. I think the fibermesh reinforcement helps with that.
It's most likely just shrinkage cracking, but I don't want water getting in and freezing to make things worse.

Hmm... Epoxy might be a good option. It's about the only thing thin enough to flow down into the crack.

Agreed. I'm not about to cut a big groove in the floor to fix a crack that is barely visible right now. That might be an option if the crack opens up in the future, but I wouldn't even consider it right now.
If it wasn't for the wet line when it rains, I wouldn't even know the crack was there.

I think even the grains in the mortar would be too big to fit in the crack. I need something that is essentially thin like water.
Thanks for the feedback,
Anthony Watson www.watsondiy.com www.mountainsoftware.com
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On 3/17/2016 1:34 PM, HerHusband wrote:

That's why I thought using silicone caulk (or, anything else that "is easily SPREADABLE") to get an idea as to what the surface *really* is like. E.g., if you put a small bead of caulk *on* the crack and try to spread it with a trowel/float and it refuses to spread (because there are no "low spots" for it to flow INTO), then you know the crack is just acting as a wicking agent -- a place to LEAD water in but not really FLOW water in.

Hmmm... that is worth knowing! We're going to replace the concrete driveway and have debated "pavers" vs. a reinforced solution. The pavers are far more work (and probably not visually appropriate) so a reinforced solution would be a big win.

Yup. At the very least, it gives you a yardstick against which to gauge any *future* "movement".

Your description suggests you wouldn't be able to apply anything "thick" (viscous *or* dimensionally). So, you want something that clings well. Mortar mix would probably flake off at the first signs of mechanical stress (e.g., sweeping the floor with a broom! :> )

You can also look around to see how your garage floor is loaded. E.g., I have a lot of stuff stored in shelving units along the walls. Not the way a garage FLOOR was designed to be used!

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Don,

Correction. I took a look today and it looks like the crack may extend 3-4 feet into the garage. Really hard to tell, the crack is so fine that it kind of just fizzles out at some point. It's only because the crack is a different color when it's wet that I can even see it.
The crack IS more visible on the 6-8" outside, where it's exposed to rain, but still not really something I can feel with my fingers. Water finds the smallest cracks though...

I'm hesitant to use anything that would cause issues with a later repair. Once silicone is in there, nothing will stick to it. :)

We've laid quite a few pavers around our place. They cost more than a concrete slab but have a nicer look. Unfortunately, they are also more likely to settle, especially if water is dripping on them, or you have "critters" that dig tunnels under them. I just replaced a paver patio this last summer with new concrete slabs:

https://www.youtube.com/watch?v
tA27vsytM http://www.watsondiy.com/20150912-patio.htm
Still, as long as you prepare a good base for the pavers they look and perform well. The upside is they are easy to take up and repair/replace if you do have problems. Concrete slabs are a lot more work to replace.

I doubt mortar mix would do anything except sit on top. Even epoxy would need to be really thin to seep down into the crack.

I have almost no loading on the garage floor. To make it easy to clean the floor all of my cabinets are wall mounted and my tools are all on wheels I can move around. The only time we have a car in the garage is when we are working on them.
Anthony Watson www.watsondiy.com www.mountainsoftware.com
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Hi Anthony,
On 3/17/2016 10:10 PM, HerHusband wrote:

Winter will be the toughest time (water freezing and expanding INSIDE the crack)

Good point. I had hoped that you could "peel" it off in a sheet. I recently used some to seal the gap between the patio and house slabs, changed my mind in one area and just peeled out this long, rubbery piece.
Of course, in my case, there was enough material that it had some strength of its own. If you end up with a thin sheet, you may find it just flakes/shreds instead of lifting, intact.
I don't know what else you could use for a "trial"...

No water dripping -- other than rain (though our rains can be very intense!)
I'm more worried about the movement induced by the cars traveling over it. SWMBO has a tendency to like to turn the wheel while the car is stationary (neatly scuffing the concrete with a few hundred miles of tire wear...)

Wow, why didn't you rent an electric breaker to chip out the cement? (you've got more patience than I; we had about half a yard by the front porch that I needed to take up...)
Clever idea to arrange the screed to ride atop the pavers and arrange for the form to be similar height! Did I miss how you set the forms to ensure a suitable grade?
And, does the downspout drain to a dry well? I didn't see that go in...
I'm guessing the white PVC is part of irrigation?
Here, we wouldn't set the (wooden) stairs against the house out of fear it would hide termite activity (tubes up the foundation *behind* the stairs)
Excellent job! Likewise in the "documentation"! (If I *remember*, I take before and after photos; usually I'm more interested in getting it *done* than I am documenting the process)

"No video with supported format and MIME type found"
(I'm guessing this was a FLASH presentation?)
Is the house built over a crawlspace? Why is the "ground floor" so elevated wrt grade?
(Obviously, the siding on the garage is elevated to coincide with that of the house?)

We, of course, don't EXPECT to have to pull them up, later. But, driveway slab is cracked which gives us an excuse to replace. At the same time, I can run some wires and pipes under the driveway (not essential but makes some things more convenient).
I'd also like to run a separate water meter to get the irrigation consumption OFF our sewer bill. But, AFAICT, that has to happen *at* the municipal water supply; not "after the meter".

If it's THAT fine, you may have a problem getting an epoxy that will adhere to the mortar *and* flow well.

We have no storage, here (no attic, no basement -- plus, house has a very "open" floorplan). So, the garage handles most of our storage needs. I've got floor to ceiling, adjustable industrial shelving lining both side walls. One third of one wall is essentially just electrical cables (SCSI/USB/printer/power cords/extension cords/patch cords/video cables/etc.). Another third is my "tool box" (hand tools). Last third (of that wall) are electrical/electronic components.
Back wall is all electronic components (~1000 of those little tiny plastic parts drawers) plus freezer chest.
Other wall has regular garage stuff, nasty chemicals, etc.
Cars like to be in the garage as the paint doesn't last (even clearcoat) with our relentless sun.
A basement would be a dream come true! "Using" the garage for anything means being *done* before sunset... :<
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Don,

We usually don't get many days below freezing here, but I want to stop it before it becomes an issue. As well as just keeping moisture out of the garage.

I picked up a tube of Sika crack sealant this morning at Lowes. Gonna try that on a different crack outside and see what it does. If it works OK, I might try it on the garage crack.

Even though I have gutters on our garage, there is still a bit of a drip line underneath them. After several years of dripping, too much sand under the pavers, and the wrong kind of sand between the pavers, they eventually started settling unevenly.
I now limit my sand layer to about a half inch and use polymeric sand to lock the pavers together and prevent weeds/moss from growing in the cracks.

Same here. My wife makes a sharp turn when she pulls in the driveway to back her car in to be ready to go the next day. Over time she has worn a bit of a circular arc in the driveway. I would be worried that constant action would shift the pavers over time. For now, we're just sticking with gravel.

Limited money and I already had the rotary hammer. It wasn't too bad to drill some holes and use feathers/wedges to pop off big chunks. The worst part was the three rows of rebar I originally placed in the concrete. It did it's job and really made it difficult to break up the concrete.

I ran a couple of string lines to set the individual forms to the right heights. That back walkway slopes in two directions, sort of gentle twist along it's length. It slopes from one end to the other, and also slopes toward the yard away from the garage. It had to meet an existing walk in the back corner of the garage, the new slab between the buildings, and the existing sidewalk along the back of the house. It turned out nice.
When I adjust the height of my screed, I include an extra 1/4 inch or so in the sand layer. After I set the pavers and tamp them down, they settle into the exact height I'm wanting. Then I sweep in polymeric sand to lock them together.

We installed the gutter drains several years ago. Since our property slopes, I simply routed the drains so they drain farther down the slope, away from the house. Works great, no erosion, and gets the water away from the buildings.

Yep, it's a bit of an experimental sprinkler system for our long and narrow back yard. It's just a length of pipe with three popup sprinkler heads that I can connect to a garden hose. That is always a difficult area to water, so I figured I would try it while I had the yard torn up.
It seems to work nice, but I did have to replace the sprinkler nozzles with low-flow nozzles to avoid overdrawing our well pump.
Nothing fancy, just a convenience.

We don't really have termites here, but there is a two inch gap between the stairs and the house. That makes it easy to clean debris as well as see if anything is going on behind.
It doesn't really show up on the video, but the bottom of the stairs are also elevated about a half inch so water can drain away underneath.

We've always taken lots of photos of our projects, both for the memories and for reference in the future. For example, we photographed all of our house walls before we insulated and sheetrocked so we could easily see where the pipes and wires were located. You never know when you want to cut a hole for an outlet or add something inside the wall.
Video is actually easier in some respects since you can just start the camera and go to work. Of course, it means a lot of editing later.

Nope, just standard HTML5 video. What browser are you using? It plays fine with IE, Firefox, and Chrome on my desktop computer, as well as on my tablets and smart phones.

Yes, 24" high perimeter wall on an 8-10" thick footing. That gives me a good 30-36" space to crawl around under the house, and keeps the exterior wood well away from the ground to avoid rot and splashback.

Actually, the garage came first.
http://www.watsondiy.com/2001garage.htm
Standard eight foot walls on the two foot foundation gives me almost 10 feet of ceiling height in the garage.
We did set the house foundation to the same level as the garage foundation when we built the house.
http://www.watsondiy.com/2003house.htm

You never know... :)
I poured a small pad outside the garage door when we built it. I tore that out a few years later to pour the walk between the garage and the house. Then we tore that out last summer to install the new patios. :)

It's always good to take care of those things before you cover it all up again.

Same here, except we did build a nice storage attic above the garage. That's where we keep all the oddball items like suitcases, holiday decorations, snow tires, etc.

Ironically, I threw out the last of my resistors, capacitors, integrated circuits, etc. last week. I've slowly dwindled them down over the years, but finally decided I was never going to use them again.

We have way too many trees for sun to be a problem. :)
Besides, my wife's car spends most of it's life at work where the garage wouldn't help anyway.

We considered a basement, but they're kind of rare around here with all the rain we get. Not to mention our property is extremely rocky and would have made a basement very expensive to build.
Anthony Watson www.watsondiy.com www.mountainsoftware.com
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Hi Anthony,
check your mail (support).
On 3/18/2016 11:50 AM, HerHusband wrote:

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On Fri, 18 Mar 2016 09:38:49 +0000 (GMT+00:00), Aardvark

NONE of the recomendations so far will work, or are even required.
Sodium Silicate is your answer. AKA Waterglass.. AKA concrete sealer. Absolutely no caulk, PL premium, mortar mix, or even epoxy stands a chance of creaping into that crack, particularly if it is not 100% dry.. Only something water-thin and not hydrophobic stands a chance of getting in and doing any good at all. A sodium silicate/water solution WILL ge into the crack, and it will seal it - it will soak into the surface of the concrete and seal that too. It gets right into the "pores" of the concrete - basically becoming "part of" the concrete.
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On Thu, 17 Mar 2016 14:20:36 -0000 (UTC), HerHusband

See if you can rent one of these. http://www.homedepot.com/p/DEWALT-Heavy-Duty-Pavement-Breaker-with-Hand-Truck-and-Steel-3-Chisel-D25980K/203070422
Use it to clean out and widen the crack. Then fill the crack with grout.
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On Thu, 17 Mar 2016 14:20:36 -0000 (UTC), HerHusband

Waterglass.
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Just get some sodium silicate - aka "waterglass". It is sold as a concrete sealer, among other things - and will seep into the crack and seal it up. (or you can make it from drain cleaner and silica-gel dessicant packs if you want to get adventuresome)
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On Thu, 17 Mar 2016 14:20:36 -0000 (UTC), HerHusband

How much of he crack is outside the door? You might just drill a hole in it, right inside the door, using a concrete bit. Then fill that hole with some sort of epoxy or JB Weld. That will stop th flow of water to the inside!
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Maybe 5-6" outside the door, and another 2" or so directly under the garage door itself. Then it extends 3 feet or so inside the garage.
Anthony Watson www.watsondiy.com www.mountainsoftware.com
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I'm inclined to use PL Premium polyurethane. If you warm it up good, and squeege it in. Might be messy though.
Greg
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replying to gregz, caitlyn ford wrote: I think you should just consult a professional about the problem so you could save time and resources while solving it.
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