Monkey Radio
Well-known member
I am getting read to do a slab soon (26x32). And was wondering if saw cutting is necessary to prevent cracks ? Or can the concrete person trawl them in and be effective?
Control joints
- Thread starter Monkey Radio
- Start date
Soffcut or troweling will not prevent cracks...it gives them a place to theoretically happen instead of in the middle of the slab. If you plan on epoxy I would soffcut it...much easier to patch than a troweled in one...either way I would defenitely do it .
Cut it into thirds and one down the middle
Cut it into thirds and one down the middle
Attachments
Saw cuts do not prevent cracks. They provide a weak spot for the concrete to crack in a controlled place. I have used Zip Strips with success. http://www.superiorprofiles.com/?gclid=CLvcsZyN57ACFQOEhwodbE7J0Q
lg
no neat sig line
dcs Inc
Well-known member
Its important to install "pathways" for concrete to crack during the hydration. Concrete tends to shrink when drying and it will find it's own path if one isn't offered. Concrete cracks from the bottom up so either install them during the finishing or cut them in real early. Waiting too long and you are only scoring decorative lines as the concrete has already cracked on the bottom. gene
OP
Monkey Radio
Well-known member
Thank you every one for your input. It will defiantly get done one way or the other.
MrMark
Well-known member
I don't think anyone really answered his question. It doesn't matter which way you go, but the troweled crack will look a hell of a lot better. I personally would not do any control joint as they are hellaciously ugly and collect dirt. My garage does not have them nor does the garage of any of the older homes I see around here. If you are going to epoxy it I sure wouldn't do it as any fine line cracking you get is going to patch with the paint; otherwise you are going to be trying to fill some sawcut.
You obviously didn't understand my answer. Zip Strips leave a flat surface without any ravine running through the shop.
lg
no neat sig line
lg
no neat sig line
LegacyIndustrial
ALLIANCE MEMBER
We offer a hard, yet flexible epoxy filler.
Can be placed under epoxy for a seamless look.
We install our own floors this way everyday with great success.
http://legacyindustrial.net/cart/hd821-crack-sealant-gel-style-p-94.html
Can be placed under epoxy for a seamless look.
We install our own floors this way everyday with great success.
http://legacyindustrial.net/cart/hd821-crack-sealant-gel-style-p-94.html
I think I answered his question quite well....
" If you plan on epoxy I would soffcut it...much easier to patch than a troweled in one...either way I would defenitely do it .
Cut it into thirds and one down the middle"
You did see the size of the slab?
The "older homes in your area" . are they that big?
How does a troweled joint look better after it's filled with dirt?
Just sayin
MrMark
Well-known member
I didn't really study your answer to study your zip strips. The guy asked if saw cutting was necessary or could he have the guy trowel in grooves. You didn't answer that. So maybe you didn't even understand the question or your own answer.
kartracer23
Well-known member
My pour was at done 11 am today, they power troweled couple hours later (was in the shade) and they're coming back to cut at 8 PM with what he called a 'green saw'. Apparently it's got a super thin blade. He was worried about using his regular saw since it was so hot out.
*And the guy doing the finish work told me about some classes he took recently...at EliteCrete.
MrMark
Well-known member
You kind of answered but did not address the basic question of whether the troweled joint was just as effective. It is.
On the size, you are right his is a little bigger. Ours are about 500 square feet.
On the troweled joint, the reason they are not done more often is difficulty and $$$$. The joint looks a lot better with its compacted smooth radiused corners than a somewhat jagged saw kerf, even when filled with dirt.
Both accomplish the same goal
Just curious...how can the troweled joints be difficult and more $$$$....expansion joints are troweled in all the time...most "concrete subs" dont even own a soffcut machine which is big $$$...I personally would rather sweep over a sawcut than a large troweled joint
I would assume also most will VCT or Epoxy the floor making it easier to fill
Just my opinion
My pour was at done 11 am today, they power troweled couple hours later (was in the shade) and they're coming back to cut at 8 PM with what he called a 'green saw'. Apparently it's got a super thin blade. He was worried about using his regular saw since it was so hot out.
*And the guy doing the finish work told me about some classes he took recently...at EliteCrete.
The green saw is a soffcut saw...good move
ConCretin
Well-known member
Personally I much prefer a saw cut joint - they are far less obtrusive and more likely to be straight. Due to the methods involved, you are also likely to get a better overall floor with saw cut joints
In order for any control joint to be effective, its depth should be 1/4 of the slab thickness. To accomplish this with a tooled joint, the first pass must be made while the concrete is still very plastic because you have to move the aggregate aside. Since you are essentially free handing the joint, it is difficult to get it straight. With a saw cut joint, you have a chalk line to follow.
With a tooled joint, you must re-tool as you finish to keep it from filling back in. The joint is typically much wider and it is likely you'll end with tool marks. Again, no such problem with a saw cut joint that is about an 1/8" wide.
I know different practices are more common in different regions but if a finisher in my area can't produce a Soffcut saw, you don't want him.
In order for any control joint to be effective, its depth should be 1/4 of the slab thickness. To accomplish this with a tooled joint, the first pass must be made while the concrete is still very plastic because you have to move the aggregate aside. Since you are essentially free handing the joint, it is difficult to get it straight. With a saw cut joint, you have a chalk line to follow.
With a tooled joint, you must re-tool as you finish to keep it from filling back in. The joint is typically much wider and it is likely you'll end with tool marks. Again, no such problem with a saw cut joint that is about an 1/8" wide.
I know different practices are more common in different regions but if a finisher in my area can't produce a Soffcut saw, you don't want him.
pauls340
Well-known member
Once you sawcut the joint, fill it with a great Joint Filler like Seal Bond CS-5200 and you can laugh at all the dirt in your neighbors joint. If you plan on epoxy coating, leave it 1/4" short and follow directions.
ConCretin
Well-known member
This is a workable though less than ideal method. In addition to being slow and dusty, the primary disadvantage is that you will probably have to wait 24 hours or more before you can cut with a circular saw. The blade spins upward, which causes 'raveling' at the edges of the cut. An early entry saw has a plate that presses on the surface and a very narrow blade that spins downward. This allows cutting to start immediately after finishing before shrinkage cracks can develop. If cracks develop before you cut, you've wasted your time - you've got cracks and cuts.
If you do you might want to make sure your outlet is GFCI rated or make a pigtail with a GFCI plug
dcs Inc
Well-known member
My pour was at done 11 am today, they power troweled couple hours later (was in the shade) and they're coming back to cut at 8 PM with what he called a 'green saw'. Apparently it's got a super thin blade. He was worried about using his regular saw since it was so hot out.
*And the guy doing the finish work told me about some classes he took recently...at EliteCrete.
Hey, I like your avitar pic. I train a lot of concrete contractors. I can think of a couple up that way. Tell him Gene said to get those cuts in early.
Interesting. I think I will see If I can rent a early entry saw. When you say the early entry saw can be used immediately after finishing. Do you mean that if the slab is poured in the morning I can cut the joints with this saw in the afternoon? Is this saw made specifically for this job? What other names does this saw go by?
OP
Monkey Radio
Well-known member
Very informative. Thank you. Now I just need to make a decision.
ConCretin
Well-known member
An early entry saw is designed specifically for this purpose and allows you to start cutting joints right after you finish power troweling. The most common brand is Soff-cut. If they have one, the rental yard will know what you are asking for.
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kartracer23
Well-known member
They were there until 10 PM last night cutting mine, but they got it done. The guide on the saw was off, so they had another guy that uses the saw more often come in and align it correctly. Then there was so much dust that they couldn't see the lines, so they borrowed my leaf blower to blow the dust as they cut. Then it got dark so they had to break out the flashlights. So it was a 4-man operation: one guy doing the cutting, one running the blower and two with flashlights so he could see. The lines are perfect, and barely noticeable.
The good news is that since it was dark, my neighbor's couldn't see the huge dust cloud over the neighborhood.
The good news is that since it was dark, my neighbor's couldn't see the huge dust cloud over the neighborhood.
Thanks.
My foundation is a stem wall type. One more question. My slab is going to be 4" thick. How deep should I cut with a early entry saw?
One more. How does the guide work? Do I lay a board down and follow it with the guide?
1" deep and follow a chalk line
ConCretin
Well-known member
Even if you lift the guide, you'll only be able to get within a few inches. You can get a little closer with a 4" grinder but that about it. You'll probably see a little crack form between the end of the cut and the wall but it's not a problem. You won't even notice it after a while.
kartracer23
Well-known member
The saw my guys used (A Husquavarna) had a 'leg' that extended out a couple of feet with a guide on it, and then another guide in the rear. Just make sure the two guides and the blade all line up straight - this one was off by 1/2" before bending it back into place. And get a buddy with a blower to help so you can see the line. It's such a fine cut that it makes a lot of dust.
So my poor is tomorrow at 6:00 am. The weather will be about 80* for a high. And we don't have shade after 9:30. The himidity is very dry here.
In talking about the logistics of the pour and speed of curing. I was told that it might be best to forgo the soft cut saw and get the slab covered tomorrow after they trowel so to slow the initial cure and prevent spider cracking. Then come back the next morning with a standard walk behind conc. cutting saw.
Does this sound like a good plan? One poster above said that I should wait 24hrs to cut with a skill saw. Why is this and would that be the case with the walk behind concrete saw?
Advice is needed please.
In talking about the logistics of the pour and speed of curing. I was told that it might be best to forgo the soft cut saw and get the slab covered tomorrow after they trowel so to slow the initial cure and prevent spider cracking. Then come back the next morning with a standard walk behind conc. cutting saw.
Does this sound like a good plan? One poster above said that I should wait 24hrs to cut with a skill saw. Why is this and would that be the case with the walk behind concrete saw?
Advice is needed please.
dcs Inc
Well-known member
If you wait 24 hours the cracks are there, they just haven't made it to the top.
mmanship
Member
My garage is a recent build about the size of yours. 30x30 inside deminsions. I instructed the concrete guys to cut 2 joints both ways. They said that would be too many. Well, all I can say is that there are hairline cracks running the length of each joint. That's what is supposed to happen. I now have the floor epoxied and the joints filled with a matching color flexible material. No ugly joints filling up with dirt.
I've had the same saw for 8-9 years, and have likely cut hundreds of thousands of feet with it personally. The only thing I can imagine went wrong was you cut a little too early, had a poor blade, an old worn-out base shoe, or you were applying some sort of side load on the blade. I've honestly sawn broomed driveways in my socks in the past and left slight marring from the wheels of the saw and still got a nice clean cut........
If you want to "fix" the spalling cut lines there are a number of ways to disguise it depending on what you're final plans are for the saw...........
I think I may have cut a little early, but I felt I needed to get it covered up. Maybe I should have covered it and then uncovered a few hrs later to cut. The saw was a rental. I don't not any thing about these saws so cant really comment on the shape of the blade or shoe. It didn't look like much of a show to me.
I want to fix the chip out at the edges. I believe I will acid stain then clear coat it. I would like to discuss how to fix it.
I want to fix the chip out at the edges. I believe I will acid stain then clear coat it. I would like to discuss how to fix it.
darkk
Well-known member
I live in Eastern Ct and the weather here is not the most hospitable for concrete. We did a 30x30x6" 3500psi slab with fibermesh in the concrete, 6 mil plastic taped under the concrete with 6"x6" raised mesh. I also placed two 3" conduit across the middle of the slab about 4" below the sand base and covered it. We started the build in 7/09 for our 2 story addition with a 30x30x13 open garage lower and 30x30x11 upper. It was 90-100 degress for a couple weeks and no shade.. I made sure I kept the slab soaking wet for 8 days, and I do mean soaking wet. We did not cut any lines in our slab, at this time we still have no cracks or hairline spider cracks in our pour. If the surface is prepared, poured and cured properly, there should be no problems with cracks.
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mmanship
Member
Many reasons for the concrete to chip on cutting. My drive was broomed. The cutting chipped out little pieces. The reason was the crew did not float down the gravel that was in the concrete. Too much gravel very near the surface. As they cut, the blade would flick out pieces of gravel and the gravel chipped out the cement above it.
If you're going to acid stain it, your best bet is to grind the joints out wider with a tuckpointing blade in the future, and fill them with an accenting caulk/grout/polymeric sand/etc... You could also add more joints to give a patterned look to it.