Crack sealer

[Joevano]

I've got a good 1/2" crack across my floor that really never changes but bothers my wife so I'm tasked with filling it. What should I use for such a large crack that will expand and contract seasonally? Fill it with foam backer first? If so, how deep should I put the foam so I get a good seal with the sealant?

 

[Zeke]

You might want to look into a gray elastomeric caulk. Sikaflex comes to mind.

 

[Chris705]

Your backer rod wants to be the width of the crack (maybe think about running a grinding wheel along the crack to make a consistent width)...set the rod about 1/4" or so below top slab level. The sealant as zeke describes above is available at HD. using a caulk gun apply the sealant on top of the rod and let it self level. Fill to top of slab (or slightly above) with repeated applications within minutes of each other. Let cure overnight and the next day or so you can cut flush to top of slab with a razor scraper.

 

[Zippercat]

If the crack is really deep or has lot of variation in width, I suggest filling the crack with sand to within about 3/4 to 1/2 inch of surface instead of using backer rod. Then use the Sikaflex self leveling as recommended above.

Sikaflex is pretty runny and will drain around the smallest of gaps by the backer rod. Also, if the temperature is under 50 F expect thicker areas of Sikaflex to take a day or more to cure.

 

[lakeroadster]

Just used Sika FlexSelf-Leveling Sealant Gray in my shop... good advice here ^^^^

Joint dimension should allow for ¼ inch minimum and ½ inch maximum thickness for sealant. Proper design is 2:1 width to depth ratio.

Don't let the tubes sit in the sun before use... product will dispense very runny.

http://www.homedepot.com/p/Sikaflex-10-1-fl-oz-Self-Leveling-Sealant-Gray-515304/207086476

 

[Armorpoxy]

We agree with the sand and SIKA method. This allows for movement.

 

[roc_on_the_rocks]

I had a similar need recently, where the varying width of the crack wasn't suitable for backing rod. Searched a bit on GJ and saw some people using Great Stuff insulating foam sealant. It worked like a charm. Just apply very little rate, you don't want the foam to overgrow too much (although it can be trimmed later). And as Zippercat just said, Silkaflex is vey runny, so if the bottom of the crack isn't sealed well, it'll keep draining expensive caulking.

 

[Les Grossman]

Get the extreme set from Legacy Industrial. Fast and looks great.

 

[rburke65]

I just have the width of the saw blade from when they cut my floor after the pour. Rather than stuffing backer rod in the saw kerf, can I not sweep sand into the cut and then use the Sika flex to fill the cut? Seems to me to be faster than stuffing backer rod into the kerf. Did not mean to hijack thread. Thanks.

 

[lakeroadster]

I just have the width of the saw blade from when they cut my floor after the pour. Rather than stuffing backer rod in the saw kerf, can I not sweep sand into the cut and then use the Sika flex to fill the cut? Seems to me to be faster than stuffing backer rod into the kerf. Did not mean to hijack thread. Thanks.

Yes.

Otherwise you'll use copious amounts of sealer.... ask me how I know

Getting tired of shop vacuuming the control joints after every woodworking project so I bought 3 tubes of Sika Flex Self Leveling Sealant at Lowes.

It'll take another 4 tubes to finish the maintenance bay.

 

[LegacyIndustrial]

Sika flex should never be buried under coatings. This will be a failure point.


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[roc_on_the_rocks]

Sika flex should never be buried under coatings. This will be a failure point.

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Hey Scotty, could you elaborate about this failure? Will the coating on the Silkaflex crack and peal (somewhat expected), or something worse?

 

[Shea]

SikaFlex is non paintable and very flexible. Coatings will not adhere well and can crack or fracture under pressure over the joint since the sealant will allow too much flex.

 

[Ch3No2]

Ardex Feather Finish if you are going to coat it...excellent results.

 

[LegacyIndustrial]

SikaFlex is non paintable and very flexible. Coatings will not adhere well and can crack or fracture under pressure over the joint since the sealant will allow too much flex.

Exactly.