Cutting lines in my floor

[mod600]

We poured the floor in my 32x64 pole shed this week. Poured half Wednesday and the other half yesterday. The cement guy put in a construction joint between the two halves, with re-bar linking the two halves together. So basically each pour was a 32x32 slab. We used 4,000 lb exterior with fiber mesh mix. He gave me his dry diamond blade to use in my circular saw to cut the lines. He said to go once down the middle lengthwise and then cut each slab/pour in half crosswise..resulting in 16x16 grid work. Cut 3/4" to 1" deep. I have overhead doors on each end, so my cut lines would go thru the door openings. Should I cut clear thru the slab so my cut line will show up outside the door when it's closed, or should I cut it short and keep the cut inside door opening. He said I can do either, but blow out/**** out the cut lines and run a bead of concrete sealant/silicon to seal the cut line back up. It cooled down that last 2 days and I've keep the doors shut to slow the curing process down. I plan to attempt this tonight or tomorrow. Any thoughts as to whether to cut clear thru the door opening or stop it short?
Thanks!
mod600

 

[alk1174]

I dont know what is recommended. On my neighbors garage they stopped the cut inside the garage. When the floor cracked it followed the cut line inside the garage till it got to the end of the cut it then went in multiple directions outside the door.

 

[Fastback]

Cut to the edge whenever possible. Get as close to the walls as possible. The crack could (will) leave the cut and sprawl out if you do not cut to the edge. If you are worried about the cut being outside use some silicone or other joint filler to keep water out.

 

[nehog]

I cut all the way to the edge. Then at the doors I (later) refilled the cuts to about 2 inches past the doors (on the inside) with filler (caulk like stuff.) If you don't cut to the edge you will get a crack from the end of the cut to the edge of the slab. But, cuts need to be made very soon after finishing the slab, so it may be too late anyway!

 

[dcs Inc]

No later than 12 hours after finish the cuts should have been placed. You may be only adding decorative lines in your concrete now. When concrete dries it will shrink. These shrink cracks form on the bottom of the slab and work their way up. Cut a little deeper if you can.

If you are attempting to control a crack with a cut and then stop it. The controlled crack will continue in a random fashion.

Was there a vapor barrier placed under the concrete?

 

[Full Size 66]

I was told within 24, preferably within 12 hours, to cut the slab. The cut lines tell the slab where to crack. The depth should be about 1/3 the total thickness... This is only what was told to me by the finishers.

 

[RCman]

Sorry to hijack, but what do you guys recommend for filler for the cuts? My cuts are about 1/8" wide. Should I wait some time before filling them? My slab was only poured last week (vapor barrier and welded wire). The cuts were made about 11 hours after the power trowel finish.

 

[Fastback]

I used 1/8" foam backer rod set just below floor level then I used a product I bought from job site supply just for this task. It was around $10 a tube iirc and fits in a caulking gun,it goes really far and self levels. I taped off both sides of the cut to make a clean edge.

I like the backer rod because it keeps the expansion cut clean and allows for things to move,I was instructed NOT to fill the cut.

 

[dcs Inc]

Did you get the Sonnoborne SL-1? I have a couple cases I keep in stock of that. It's the self leveling version. The fill is suppose to be twice the width for the depth. Or is it the other way around.... I'd have to check for sure. I've dealt with those guys heavy when I was still pouring concrete. I still go in and say hi to Ryan, he runs the decorative side of things down there.

I used 1/8" foam backer rod set just below floor level then I used a product I bought from job site supply just for this task. It was around $10 a tube iirc and fits in a caulking gun,it goes really far and self levels. I taped off both sides of the cut to make a clean edge.

I like the backer rod because it keeps the expansion cut clean and allows for things to move,I was instructed NOT to fill the cut.

Hey Fastback, If you are ever on the south side, drop by my showroom and training facility. I'll give you a tour. I'm on the east side of Greenwood airport off Emerson Ave. Maps on my webpage.

 

[Fastback]

Hey dcs, I did not realize that you were that close...(I'm over in center grove).I do want to check that place out.

I may be over at the rock n roll car show next weekend at the gwood airport, you should check it out!

 

[mod600]

No vapor barrier under the slab. We kept the door shut on the shed since we poured to slow down the curing process. It cooled way down since we poured, low 40's over night. I talked to the cement guy this morning and he said to cut it to the outside edge and as close to the wall as I can get and then silcon/seal the lines. If I cut it tomorrow it should be good to go. We'll give it a shot in the morning. Both halves are still very dark gray in color. The part sticking out past the over head door on the first pour has lightened up some.
thanks for the replies.

 

[Fastback]

Renta walk behind cutter, those are awesome.

Sofcut is what was used on my floor.

 

[dcs Inc]

Hey dcs, I did not realize that you were that close...(I'm over in center grove).I do want to check that place out.

I may be over at the rock n roll car show next weekend at the gwood airport, you should check it out!

Ha... Yes we are neighbors. I wondering if the car show will be going on the same time as the Greenwood fly-In. I have a light sport aircraft hangared at Franklin Flying field. Been trying to get a hangar at Greenwood but haven't had time to push it. Keep in touch. I have a class I have to teach on the 20-21st. that may be the same time as the car show.

 

[joes169]

You mentioned that it was a pole building. I would, w/o a doubt, cut at the center of each post, if it is indeed a pole building. That's likely going to bring the "squares" down to the 8-10' range, which is ideal IMO, depending on the thickness. The 90 degree corners of the post serve as a point of re-entry for the concrete to crack, and should be respected IF you're concerned about random cracking.

That being said, the floor should have been sawn a few days ago already. I can't tell you how many times I've sawn with the Sof-cut in my socks to keep from marring the green surface. One more thing, don't bother with renting a SOfcut saw now, it will struggle with how hard the concrete already is.........

 

[bglad]

HD sells a product that fills joints. Comes in a quart plastic container. I'll repost when I find it.

 

[bglad]

It's made by quickcrete and called crack fill

 

[Fastback]

It's made by quickcrete and called crack fill

Don't confuse a crack filler with a joint filler you Should use a pliable soft filler for your cuts not a hard crack filler.

 

[bglad]

The one complaint that I have about this stuff is that it shrinks. Feels soft, I can push my fingernail into it.

 

[drackett_19]

I was told to use Sonolastic NP1.

http://www.saudi-basf.com/EN/PRODUCTS/JOINTSEALANT/SONOLASTICNP1/Pages/default.aspx

 

[Fastback]

Dracketr,that looks ok but I don't know if it's self leveling? I used cheap foam backer rod and recessed it slightly and used a self leveling product, I will look and see what I used. If its not self leveling it may not flow into the joint without using a putty knife etc..

The stuff I used is really common and not expensive and specifically for horizontal cuts.

 

[mod600]

I got my lines cut as directed by my concrete guy. I cut thru the door openings. I picked up some joint filler last night in town. I believe I got the NP2 stuff, they had NP1, but the NP2 was self leveling. Where would I find the foam back rod? I cut 1" deep and this stuff is good for up to 1/2" deep. I was running short on time, so I didn't look too hard.
Thanks!

 

[Familyof8kids]

It's made by quickcrete and called crack fill

It is called you have to be smoking crack fill.

It fills but will shrink. I have used it on many rental properties and after 6 months will start popping back up in chunks.

 

[dcs Inc]

I've filled thousands of feet with the sonnoborne product. the NP-1 and and the SL-1. has held up well after many years. If you dont clean the joint/saw cut it will loose contact on the edge. It's like trying to paint on top of sand. Are these the best products. NO, you can find better but for the costs they are the best thing out there.

 

[joes169]

One more vote for SL-1, I've used it with great results both in the past and currently. As for the backer rod, it's a must IMO. Most every sealant is designed to adhere to 2 sides only, and not the bottom of the fill. The reason to use the backer rod is not only to minimize the depth, but to keep it from adhering to the bottom and drastically limiting the sealant's abilty to "stretch" on an active control joint............

 

[dcs Inc]

Well said, joes169. On an active joint if it can't expand on the bottom it will rise on the top and create a speed bump.

 

[mod600]

Ok, I was wrong..the stuff I picked at Menards is Lotite PL-S20...Polyurethan Masonary Sealant, Concrete Crack Self-Leveling... Not sure how that compares to the SL1 stuff...maybe I'll check Home Depot or Fleet Farm to see if they happen to carry this SL1 stuff that everyone is recommending. I'm planning atleast sealing from the edge of the slab to the inside of the door. cement guy said it's up to me if I want to do the whole works, alot of guys leave the cuts open.......

Where would the foam backer rod be found? My cut is probably 3/16" wide by 1" deep...would I run two pieces of the foam backer rod and then top it off with a bead of the sealant?

thanks!