Serious question, did anyone else spend years doing control joints wrong?

I was on a commercial slab pour in Calgary about 3 months ago. The general contractor's son was there learning the trade and he asked me why I was cutting my joints so deep. I told him that's how I always did it. He pulled out his phone and showed me a video from a concrete engineering seminar that said cutting too deep actually causes more random cracking because it weakens the structural integrity of the slab. Turns out for the last 15 years I was cutting to almost half the slab depth when most codes only recommend a quarter of the depth for standard floors. That kid saved me from probably hundreds of future callbacks. Any of you guys ever have a moment where some random person called you out on something you thought was standard practice?

3 comments

3 Comments

theathomas25d ago

Man that story about the general contractor's kid hits close to home. I had a similar moment a few years back where some young engineer fresh out of school pointed out I was doing my joint spacing totally ass backwards. I always thought closer together meant less cracking, like safety in numbers or something. Turns out I was making things worse by leaving too many weak spots in the slab, basically turning the whole floor into a checkerboard just waiting to fall apart. Makes me feel like a real dummy looking back, but hey at least we learned before everything cracked to hell, right?

milesrobinson25d ago

Nodding so hard right now, I've totally been there too.

jenny_fox25d ago

Actually, safety in numbers kinda does work for rebar but not for joint spacing. The closer together you put joints, the more control you have over where cracks happen, not the other way around. The real problem is when joints are too far apart, then you get random cracks everywhere. Your young engineer might have been right that you were doing it backwards, but maybe not for the reason you think. Either way, glad you caught it before the whole thing turned into a mess.