Control joints in shop slab??

[shibaura_4043]

Well doesn't look like it's going to happen, he standing me up today, says he can't make it until tomorrow. I'm pretty pissed off about it too.

Update: he said he'd be here in 1 1/2 hours. I think you guys convinced me they are a good investment... I hate looking at cracks... lol. Now on the 40 foot width there will be two cut lines running the 60 foot length. Where Would you place them, remember I have 2 bay doors 12' wide . Would you just run them equally spaced even if it puts them offset in the bay drive-in areas?

 

[Gunny]

One pretty steadfast rule when dealing with concrete is that it's going to crack, doesn't matter about your sub base, the temps, how thick it is or anything, it's going to crack.

You can control a lot of that by putting control joints in

 

[nybirdman]

I worked on big construction for 25+years and they always sawed control joints.My last personal pour for my garage I made it in two pours and left the form(3/4")between and it has never cracked(10 years)

 

[fried1765]

Well doesn't look like it's going to happen, he standing me up today, says he can't make it until tomorrow. I'm pretty pissed off about it too.

Update: he said he'd be here in 1 1/2 hours. I think you guys convinced me they are a good investment... I hate looking at cracks... lol. Now on the 40 foot width there will be two cut lines running the 60 foot length. Where Would you place them, remember I have 2 bay doors 12' wide . Would you just run them equally spaced even if it puts them offset in the bay drive-in areas?

You have a choice!
Do nothing = spider web cracks.
Cut control joints = neat looking job

 

[Birdhunter1]

The floor in my 30x50 shop is 5" thick and was poured in September 2010. The cut lines are in 12' x 12' squares about an inch deep. So far there are no cracks in my floor and we have temps ranging from just below 0 in the worst of winters to about 110 in the worst of summers.
For what it's worth if you're worried about the lines in your floor being grooves just caulk them shut. It takes about a case of caulk but in 7 years I haven't complained about my floor one bit or even noticed them when rolling stuff around. Also the lines make great reference points when laying out the misc large frames that end up being built in the floor.

 

[bspeedy]

Well doesn't look like it's going to happen, he standing me up today, says he can't make it until tomorrow. I'm pretty pissed off about it too.

Update: he said he'd be here in 1 1/2 hours. I think you guys convinced me they are a good investment... I hate looking at cracks... lol. Now on the 40 foot width there will be two cut lines running the 60 foot length. Where Would you place them, remember I have 2 bay doors 12' wide . Would you just run them equally spaced even if it puts them offset in the bay drive-in areas?

I would space them equally. You won't notice them after two weeks.

 

[RNeumann]

You need them cut! In general we would go a max of 15'x15'- some really big stuff we would go bigger. If worst comes to worst you can cut them yourself with a chalk line and skil saw with diamond blade. They should be 3/4" deep. If you have steel posts use those as starting points. You want it done in the first few days.

Most of the time a slab on grade house doesn't get control joints as it is covered by carpet or other flooring. Anything that is exposed like shops, garages, sidewalks and driveways get expansion joints. I always prefer the cut joints but it does require the contractor to return the next day. That's why some do the wet joints that are "cut" in as the concrete is finished.

 

[6sunset6]

I put control cuts in myself . 10' centers The day after the pour Diamond blade in a skill saw. As deep as it would go . Followed a chalk line. 2 20' and 1 30'
Could have flooded it with water but just went dry. Other than a hugh amount of dust it worked great. With a double insulated tool and a little care water is ok. I have cut stone slabs with the same set up and water.

 

[RNeumann]

I put control cuts in myself . 10' centers The day after the pour Diamond blade in a skill saw. As deep as it would go . Followed a chalk line. 2 20' and 1 30'
Could have flooded it with water but just went dry. Other than a hugh amount of dust it worked great. With a double insulated tool and a little care water is ok. I have cut stone slabs with the same set up and water.

Too deep and you cut the rebar- not good! A skil saw cuts about 2" deep at max depth

 

[6sunset6]

Good point it was a 5.5" slab I did not cut the rebar.