To cut or not to cut..... control joints

[bill9860]

The pad for my 26w x 28d detached garage was poured Friday and and the builder wants to cut control joints. Not sure it is a good idea, bad idea or just a "why not" because it doesn't hurt anything.

I have had two houses with unheated garages that had no cuts. The first one was 20+ years old and no cracks. The current house is 15 years and no cracks.

This detached garage will be heated and have a 2 post lift. I realize the last thing I need is a crack headed toward one of the floor plates. This is a floating slab sitting on a lot (say a foot or so) of compacted gravel if that makes a difference.

Thanks in advance for your views.

 

[aemp]

hi,done my garage floor48-25 in 2003 and did not cut it.it has hair line cracks in it now and im told its because i didnt cut.have to say my reason for not cutting was i though it would look bad.i am based in ireland

 

[Cryptic1911]

I had planned on a 2 post in my 30x30, so I didnt cut any joints because I didnt want the edge of the cut to be near the post in the center.. turns out I am going to get a 4 post instead for other reasons, but I'm still going to pass on the cuts. Thing is, my floor is 6" thick, so I would be a bit safer than someone with 4" (or so I would think).

how thick is your slab?

 

[bill9860]

Slab is overall 5" 4000 psi but I have about a 6x15 area of 8" where the lift posts will be.
That gives a bit of cushion for ultimate positioning

 

[ket-tek]

Slab is overall 5" 4000 psi but I have about a 6x15 area of 8" where the lift posts will be.
That gives a bit of cushion for ultimate positioning

I have two control cuts in my 28x38 6" pour, and about a year after the pour a hairline crack appeared right in the middle of the garage and over a few months it spread in the long direction of the garage, and stopped when it hit the control joints in both directions, as the slab was cut into 1/3's. So the crack is only about 12'-14' long instead of eventually continuing to go the entire 38ft length. The cuts also stopped the crack before it got to the area where my lift is located..

So although I thought I didn't want any at first I'm now glad they were there..

 

[Jack90210]

Monolithic pour, or footers poured separately?

Rebar, or WWF?

Any additives, like fiberglass?

I'm not an expert, but I did a lot of research online and decided to cut a joint in my 24x24 (as well as on the "extra areas" of floor connected to the 24x24 square).

EDIT: Took me a while to find it, but here is a great post in a similar thread from 2008.

 

[Joe69]

I wouldn't pour a slab without cuts, but I live in Indiana.

Joe

 

[Steve in Mi]

I saw cut control joints on my 28' X 48' shop floor on a 12' X 14' pattern and would do it again. I see a couple of hairline cracks coming out of the end of the saw cuts running the 4" or so to the outside edge of the slab. IIRC the recommendation was to get them in within 24 hours to stay ahead of any cracking.

 

[s_ontario]

Cuts 10' to 12' squares at least 2" deep

 

[wormwood]

My personal motto:

If in doubt: cut it out.

 

[scooterseats]

My 30' X 40' is a monolithic pour with fiberglass filled concrete. It is three years old and n cracks yet, even surface ones. The pad is on compacted sandy clay with a vapor barrier and a pole framed building over it.

 

[Torque1st]

I just had over 1500 sq ft placed and I had 1.5-2" deep cuts in it. Once you have the cuts cleaned out fill them with some self leveling sealer.

 

[ddrewyor]

I have a 30' x 40' with a 4" slab cut at 10' intervals 1" deep. The cement was air entrained 6 sack with fiber and wire mesh reinforcement. Only cracks are right in the control joints. I have had forklifts and heavy equipment in and out for 9 years. Just recently poured a 30' x 22' pad out front and it was saw cut also.

Dave
















'
________
Silver surfer vaporizer

 

[6768rogues]

Concrete shrinks. Cut the joints. A good base and no heavy loads will not stop shrinkage cracks.

 

[gwis2]

Even with fiber mesh, wire mesh, AND rebar buried in it concrete can still crack. The purpose of a control or expansion joint is not to prevent the crack, but to encourage the cracks to go where you want them to go. Torque1st is right in saying get the cuts and fill them in with a concrete caulk...

 

[Bfoughty]

40 X 40 building, 11 1/2 inch thick concrete (this due to the mexican labor sitting down once the boss left and not putting the sand in) monolithic pour with rebar in the footing and I cut the floor. Here in Oklahoma it's a given....concrete will crack and if you don't have termites...just wait.

 

[c39er]

My slab was poured with "Zip" strips intalled in the wet concrete. No cracks in 12 years.

 

[bill9860]

Thanks to everyone for the input. And thanks to jack90210 for taking the time to find that pld post

 

[twostory]

You are suppose to make the control cuts within 24 hours of the pour. The cut control where the concrete will crack.

The concrete cracks form shrinkage, this starts immediately after the pour. So if you do the cuts too late, it may start cracking before you cut it.

 

[Gary S]

My recommendation is to cut it. When I poured my slab, the building inspector recommended I cut it. I did, and within a couple of months, The concrete cracked along every cut like it was supposed to. I filled the cracks with a flexible sealer, and now they get wider in the winter and narrower in the summer.

 

[srmofo]

I cut my 24x36 into 12x12 pieces. I noticed my first hairline the other day right from the stem wall to where the control joint started. You cant run the saw all the way to the wall. I guess they did their job.

 

[dtj5]

My 24x24 was poured with zip strips and perfect hair line cracks dividing my floor into quarters developed over the cure time right where the zip strips were placed. Looks kind of nice....