Control joints in shop slab??

[shibaura_4043]

Had a 40x60 4" slab with 24" beams poured yesterday afternoon. Should I cut control joints? I've got several contradicting opinions. I'd like to get suggestions from people who did and who didn't go with control joints. Also, I'm pouring my house slab in about a month. I, trying to decide on post tension vs rebar(5/8 rebar in slab and beams on 12" centers) Again I've got a lot of contradicting opinions. Trying nail down a decision and its proven difficult lol. Thanks in advance.

 

[bspeedy]

I would cut the control joints. The slab WILL crack. Looks a lot nicer when it's in a nice straight control joint than in the ugly zig-zag pattern.

And I think the window for cutting the joints is pretty tight. Better git er done.

 

[jb1390]

I would cut the control joints. The slab WILL crack. Looks a lot nicer when it's in a nice straight control joint than in the ugly zig-zag pattern.

And I think the window for cutting the joints is pretty tight. Better git er done.

+1. Concrete will crack - it's up to you whether you care where it cracks.

Also, ideally cut the slab about 1/4 of the way through. For a 4 inch slab, that's a 1" cut. The deeper you go, the more likely the crack will follow the joint. If it's just scored on the surface, it might not follow the line. 1/4 of the way through pretty much guarantees it from what I recall.

 

[Shaneard]

Our shop floor at work doesn't have them. It made its own. The one that looks like it's been sawed in is actually where they poured half the building then did the other half.

 

[shibaura_4043]

Our shop floor at work doesn't have them. It made its own. The one that looks like it's been sawed in is actually where they poured half the building then did the other half. <img src="http://www.tractorbynet.com/forums/attachment.php?attachmentid=497141"/><img src="http://www.tractorbynet.com/forums/attachment.php?attachmentid=497142"/>

Are you suggesting I cut them too or it doesn't matter? Also, the saw lines will be cut directly in center or off center a couple of feet in the bay areas ( doors are on the 40ft side) im worried it will look like crap.

 

[Argonne]

My 30 x 70 shop was poured in early June (7 months ago). After curing the concrete, I added up the hours and materials to cut control joints, and decided to put that money into electrical stuff, so no control joints. About 3 weeks ago, the first crack appeared, running front to back across the width of the slab and about 20 feet from an end wall. The crack is about 1/8 inch wide and 1/16th height offset at this time.

So far I am happy with my decision, as I don't much care what the floor looks like.

My soil is all clay and famous for it's instability....cracking and settling were assured. I did pour a gravel base and let it settle for 4 months before building, and the construction is dug (as opposed to driven) 6 inch posts with all framing 2x6 stick built, so the building is not built on the slab, but the slab poured in the building. Had it been otherwise, I might have been more concerned with predictable cracking.

Anyway, so far so good. Still satisfied with my decision.

 

[Shaneard]

Are you suggesting I cut them too or it doesn't matter? Also, the saw lines will be cut directly in center or off center a couple of feet in the bay areas ( doors are on the 40ft side) im worried it will look like crap.

I am suggesting you cut them. If they are done right, straight and even you won't pay any attention to them after a while but you will if you have cracks. I been here 21+ years and these cracks annoy me, lol.

 

[Snobdds]

This is a no brainier...cut the joints. I had no idea people actually opted to not add control joints. This is the first I've ever heard of that...

 

[shibaura_4043]

This is a no brainier...cut the joints. I had no idea people actually opted to not add control joints. This is the first I've ever heard of that...

People just don't cut them around here because they will inevitably crack outside the joint lines

 

[4570Man]

My floors are cut. There are a few cracks outside the cuts, but they are small and hardly noticeable.