expansion joints

[sting ya]

How important are they ? Ive just built a 30 by 40 garage and the mason feels they are not needed. Any opinions ? I live in ct

 

[nehog]

You talking control cuts which are cut about 24 hours after the pour? They do minimize cracking in random places, but are not absolutely necessary. If the slab is already poured, and you've built your garage on it, well... It is a bit late, so technically them mason is right!

 

[iajonesy]

That really depends on where you live. If you live in an area where there are temperature extremes,like the mid-west,they are necessary. They are there to prevent your concrete from riding or shifting do to expansion and contraction during hot and cold cycles in the weather. Without the joints your floor will develop cracks. They can be added after the floor is cured. A concrete saw is the fastest way to add them. Hope this helps a little bit.

Mike

 

[ConCretin]

A concrete slab is most susceptible to cracking in the hours and days immediately after it is placed - the concrete's strength is low and it likely to contract as it cures. If you don't have shrinkage cracks now you probably won't get them. Shrinkage cracks can be present but very difficult to see. They'll show up with seasonal changes.
Cracks can occur later and saw cut joints will still give the crack a place to go where they won't look bad. Proper reinforcing is the best defense against this type of crack.
If you would be dismayed with a random crack or two, you should go ahead and saw cut, otherwise you're probably fine without them.

 

[bmwpower]

Are you really referring to expansion joints? Or control joints? They are different.

 

[sting ya]

I was talking about control joints "cuts" The floor was poured 14 days ago and it is all ready framed and roofed. The foundation was done properly with 8" compacted gravel, rebar and mesh, 5 " thick floor. Just curious as to why he didnt feel necessary to cut. Just lazy? or not needed.

 

[AndysMBgarage]

I wet my slab every morning and afternoon for 14 days after the pour and I have almost no cracking. As our outside temperature is quite mild, the curing time is easily slowed by wetting the slab.

 

[smallbloc]

With the rebar and mesh you should be OK. Your concrete is 90% cured after 7 days, I used to test the stuff.

 

[nehog]

Agreed, with mesh and rebar you should be set... I have no cracks in my 30x60 slab with rebar (only) which is about 5-6 inches thick.