Joints in slab

[ACDNate]

Poured a 30x60 slab today.

I can't find anything definitive in my googling. What should I be doing for joints in the slab?

How many cuts? Depth? layout?

Thanks for any help

 

[Steve in Mi]

One cut right down the middle lengthwise then sections 15 or 20 feet crosswise. Depth can vary depending on thickness, I forget the rule of thumb. I cut my 5" thick pour ~1-1/8 inches deep. Use as narrow a blade as possible, 1/8" works well.

 

[nehog]

FWIW, we cut my 30x60 into 10 ft squares.

 

[Leaflessshadetree]

10 x 15 ft rectangles would layout OK. 15x15 or 15x20 if you are confident in the underlying base and strength of the concrete.

 

[JWVan]

Depth should be 1/4 of the thickness of the slab.

 

[ACDNate]

Center line and 20' was what I was thinking.

Thanks!

 

[ConCretin]

Get them cut asap. The purpose of the saw cuts is to induce shrinkage cracks where you can't see them. These cracks occur very early when the concrete is shrinking the most and hasn't developed the tensile strength to resist them. The longer you wait, the more you risk a random crack. Depending on weather and other factors, 24 hours is probably too late.

As has been mentioned, cut 1/4 the depth of the slab and make the panels as square as possible. 10x10 would give you more insurance but 15x15 would be Ok too.

 

[ACDNate]

Get them cut asap. The purpose of the saw cuts is to induce shrinkage cracks where you can't see them. These cracks occur very early when the concrete is shrinking the most and hasn't developed the tensile strength to resist them. The longer you wait, the more you risk a random crack. Depending on weather and other factors, 24 hours is probably too late.

As has been mentioned, cut 1/4 the depth of the slab and make the panels as square as possible. 10x10 would give you more insurance but 15x15 would be Ok too.

hmm, rut roh. No way to get them cut within 24 hrs. Earliest would probably be monday afternoon which would be 48hrs