Concrete on barn floor

Don-WI posted about hearing a loud cracking sound coming from his barn, after putting in hay. I said I have toyed with the idea of pouring 4 inches of concrete with re-bar/wire on the floor. A few experts made some comments that this would not be such a good idea , and should talk to a pro before going a head with such a plan. And that , this would not spread out the load. Well around here I know of at least a dozen bank barns that have the hay loft floor poured over with cement. They drive 10,000 lb tractors with loaders in the barn and stack large bales. The concrete pad , once set up adds structural strength to the whole building. One barn near me has had this kind of hay mow floor for over 30 years. Sorry experts that say it will not work, and sound the alarm. It works, go figure. It also seals out drafts from up stairs in winter. Bruce

I see nothing wrong with it, as long as the structure can hold the dead load (weight of construction materials) and the live load (dead load + whatever you"re going to put on it)
A yard of normal weight concrete is 2 tons, at 4" thick that"s 81 square feet.
The important thing is who is going to make the call.

There are several barns near me that have a span-crete floor... they are as strong as the posts that hold them up.

There is a down side to them though. The concrete floor can sweat, and add a nice layer of mold to the bottom of bales stacked on the concrete. Been there, and done that!

its really the timber floor underneath that is holding up the whole load. a lot depends on the support beams and how far they span.
I have designed many concrete slabs and the critical criteria is the distance they have to span

I worked in the concrete supplier side of the industry for 25 years and yours is a situation where you need the services of a structural engineer.I've seen floors and walls collapse while they were being poured, at 4400 lbs a yard concrete needs strong support and in the right places.

The man who put my pole barn floor down wanted 6 inches and wire. He does this for a living, does good work.

My barn is only 30x40. It was a continuos pour. Only forms were the pole barn walls and a board to close up door opening.

I shot the grade with a self leveling rotating laser. Put 16p nails in each barn post for a reference point. Set up laser and shot a few points as he was putting concrete down.

Day later he came and cut in lines. Floor hasn't cracked, 5 years later.

10 years ago, he put a drive down for me. This time he used 2x6 for forms, wire. It too hasn't moved or cracked.

Go a little heavier than 3.5 inches.

Typically, you need to detail the as-built conditions and I would want a site visit by a qualified engineer to inspect the structure as is prior to any further steps being taken.

I'm having trouble understanding what you want to do. Do you want to install a concrete slab/floor over an existing wood framed. elevated floor with its associated framework/structural members supporting the new floor and the live loads of tractors or similar imposed on it ?

As built conditions need to be investigated and being wood, it needs to be verified that all critical members are intact, knowing wood can decay, crack, be compromised by insects and or the overall condition, of how many years, cycles of previous loads. All of it needs some analysis, and at some point it can be determined that what you have will support the weight you want to place on it, both the concrete and the live loads imposed, point loading etc.

Knowing of a dozen barns like this means nothing, its your barn that counts, those barns don't support your loads, I'd isolate my thoughts of what others have done and focus on what you want to do with yours.

I've been on the construction side of this for many years and there is no way I'd even consider attempting to build what you suggest without having an engineer design it first, then review that for constructability, utilizing a plan to erect, support, shore, the decking for the purpose of placing the slab.

Its a structural element, with a lot of unknowns, there is just no logic in arbitrarily basing any rationale that well it works and you so called experts are wrong, we have done it here, there and the other place. That don't mean squat, to me anyways, someone who constructs buildings, I want as built conditions verified, I want the structural components analyzed by a qualified professional, I want to KNOW without question that the design works because the calculations prove that it does, based on the as-built conditions, and that it can be built, some designs are great but are not friendly to a builder at all.

Sure, I've heard well I don't need no engineer to tell me this or that, I know what works, I'll build it, and there are several others built like it, all it takes is one failure, one anomaly unique to yours, one oversight, one hidden problem or something unforseen, unchecked, and someone may get killed, + all the work you paid to have done is lost and then some. That is destroyed and how many other things similar could go wrong if it fails.

With anything structural of the scope of what you are considering, its foolish to proceed without any care to the above, there needs to be some redundancy and some additional safety factor built in, it takes an engineer to analyze, run some checks, and perform some calculations.

I just don't believe this is sound practice, you or someone else's life could be put at risk if it fails.

The idea you're promoting is utter rubbish from a structural standpoint. It may be that the barns you see done this way are simply overbuilt enough that the posts can carry the load... but the idea that the floor will give strength is absolutely crazy. Something still has to carry the floor. That 4" of concrete will probably come close to the carrying capacity of some structures alone, never mind adding the weight of whatever is stored in them.
It would not be me pouring concrete in that situation unless I was fully content that the walls, beams and posts would carry it.

Rod

I would think a couple layers of 3/4 plywood would give you a heck of a lot of added integrity at a small fraction of the weight, no?

I hear what you are saying Rod, and understand. All of these Dutch style barns that have had this done are/were over built. All but two are dairy tie stalls,with their original wooden vertical support post , replaced with steel columns. My barn has a steel post every eight feet, under the main load bearing beams. No question the structure needs to be sound, no argument. Bruce

It sounds like its beefed up, my only point is safety, really enjoy seeing all the photos of what you do in your neck of the woods, by description it sounds risky, hate to see something go wrong, but if you have enough structure, it checks out and is "construct-able" meaning you may need to provide shoring and falsework to place a slab, could be possible, like you say its overbuilt, let someone calculate the and figure the overage, and see what you have.

You'll have to pardon me, as a builder or anytime in that role, we never make any moves or construct anything of that scope or scale without a design, and or if a change occurs and we determine, well this will work or we could potentially do that or have an alternate, it and with all its details are presented to an engineer for approval, again, only point is safety, you just hate seeing things go wrong that should never occur, seeing what you do for a living, with a little glimpse here and there, its like hey uhhh, eerr umm, you may want to rethink that just a bit LOL !!!!!!!!!!!!!