I finally get why folks swear by the 3 4 5 method for squaring concrete forms

I always figured a speed square was good enough for setting up small slabs. Then I watched a video from a guy named Mike out of Kansas City who showed how being even a half inch off on a 12 foot form throws everything out of whack. He laid out a 3 4 5 triangle with string and stakes, and the corner came out dead nuts square. I tried it on a 4x4 patio pad last weekend, and my diagonal measurements matched to within 1/16 of an inch. Way easier than eyeballing it with a framing square too. Has anyone else here switched from squares to strings for bigger pours?

2 comments

2 Comments

ryanf6620d ago

Man I used to be the same way. I had a speed square in my pouch for years and thought that was all I needed. Then I helped a buddy pour a 10x16 garage slab and we were off by almost an inch on one corner. It was a mess. After seeing that same kind of video, I grabbed some stakes and string and tried the 3 4 5 method on a 6x8 shed pad. The difference was night and day. My diagonals matched up perfect and the whole thing felt way more solid and square. I won't go back to a speed square for anything longer than a 4 foot form now.

emmap1619d ago

Man, come on. Is a half inch really gonna ruin your whole pour? I've done plenty of slabs with a speed square and never had a problem. Sounds like overthinking it to me. @ryanf66 I bet that 10x16 garage was off cause of something else, not your square. I mean you're setting forms in gravel and dirt, not a machine shop. A little wiggle room is normal.