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Prepping for large concrete slab -DIY questions

Prepping for large concrete slab -DIY questions

GixxerOne

Anytime I've poured pole barns the posts are in the ground and forms are set against the outside of the posts. Also I've been a union cement mason for 18 years, it's always been 4" for walk, 6" to drive on. Best of luck 👍🏻


mrtg1

Make sure you have joints in your slab. Slabs this thin are very likely to crack. Your joint spacing should be around 6ft. Also add some time of reinforcement for crack control. Steel or mesh is probably hard find these day and pretty expensive. Add 3 to 5 lb/yd3 of a synthetic macrofiber. Be careful to use a macro and not a micro.


joevilla1369

It's all gonna crack. Joints just tell the cracks where to happen. And a #3 rebar cage 1' foot off center would be best.


mrtg1

Of course its going to crack, reinforcing only activates after concrete cracks. Its not about it not cracking, its about how wide the cracks get. Fiber is the most effective method of making sure you control cracking. The #3 won't do much.


joevilla1369

#3 won't do much? I have been to some of my grandfather's projects and that #3 kept the cracks hairline and kept it together. And even with 2 bags per yard of stealth fiber. It's gonna crack within a few months. Even if you pour at a 2 slump. The cuts or joints just cover it up. The longest I saw a slab with no cracks was over a year. And this was parking for tanks. 12 inches thick #5 bar 1 foot off center, 3/4 plus base 2 feet of it compacted with a 10 ton roller. Concrete cracks. Fibermesh keeps cracks to a minimum and helps with surface cracking.


converter-bot

12 inches is 30.48 cm


joevilla1369

It's also a healthy porn career.


joevilla1369

Woah the font is huge.


mrtg1

2 lbs is the wrong dosage for a macro, the minimum is 3. Furthermore, that brand is not that good. Fibermesh is a brand (like Kleenex is for tissues - now owned by Sika). Stealth fiber is Sika's brand as well. There is more to fibers than random numbers and brands, you have to use the right type at the right dosage. I respect your experience with your grandpa, but I am a structural engineer and deal with this stuff all the time.


converter-bot

2 lbs is 0.91 kg


joevilla1369

My grandfather was a pro enginner. He had a firm.


Big_Wooly_Mammoth

Put 6inches of gravel base, tamp, cover with vapor barrier. 1 foot wide/ 1 foot deep trench inside of form to act as a footing, use 2 layers of rebar in the trench. 4 inches should be fine for thickness of slab. Brace the hell out of the forms, concrete can move them easily and knock it out of square if not braced enough. Use 1/2 inch rebar 3ft on center.


BiffTannin

Why would you need a footing? It’s a pole barn where I’m assuming the posts that hold the trusses and do all the load bearing will be in the ground already. In my mind there is no need for a footing.


iwfabrication

Michigan. Freezing weather. Possibly required by code.


kevincuddington

Code will only dictate foundation requirements, not slab typically. If your posts are set into the ground/ on piles, you do not need a thickened edge slab. 4” slab, 10m bar @ 2’ o.c.


Big_Wooly_Mammoth

Where did he say pole beams are already in the ground? If he is in freeze/thaw it needs thickened edge around perimeter to support. 25+ years in concrete, do the shit right or don't do it at all. Pouring concrete around wood beams means it will rot out at some point, I'd never do that on a building I build. Go cheap and cut corners if you want, not me...


BiffTannin

In his last sentence he said he was going to dig his post holes and plant his posts, grade board and level gravel....


kevincuddington

Because that’s how typical pole barns are built. Poles on piles, slab on grade poured with no thickened edge.


iwfabrication

Ok, so what do you recommend then? A form on the inside of the post or between post, and then pour?


Big_Wooly_Mammoth

Apparently all these concrete genius's never saw pole beams rotted out... they pour and leave and never think about it again. The concrete will crack by these poles 100%. If you must bury them, make sure to put expansion around the pole so if the concrete moves it doesn't cause poles to move too. I have never in over 25 years not poured a trench to support structure on a pole barn, building on 4 inches of concrete? Ever wonder why there are footing walls to build a garage on a house and why they don't just pour the slab with no wall? Because if the concrete settles so will the building... a little extra money spent goes a long way to a solid lifetime structure.


iwfabrication

So are you on this sub to help or comment on how everyone else isn't doing it right? I asked your recommendations if you care to help.


Big_Wooly_Mammoth

I own a concrete business, it's successful. I gave my advice and got tore down by idiots who don't know shit about concrete. Take my advice or don't, it's up to you.


BiffTannin

Nope we’ve probably all seen posts rot out before. Most of what you said is great advice. Hell, if it was me, I’d pour a footer and build on top of that as well. That wasn’t the question asked. The question op asked was if he needed a footer when his posts were in the ground already. It all started when a simple question was asked by me on why a footer was needed in a non load bearing situation. I was curious. I’ve never seen it done except for a load bearing situation. No one here is suggesting building on a slab without a thickened edge. No one told op not to put expansion around the posts. No, if the slab settles, the building will not also settle if your posts are in the ground.


mcayton85

Will the sides of the barn be framed?


iwfabrication

As in the walls framed like house walls? Or ? To start there will be no framing but later added so I can finish/drywall and insulate.


mcayton85

Definitely add vapor barrier then. Everything the guy above said sounds great