Is this good enough for support??

[gregzz4]

Originally Posted by Jeff000

Doesn't make sense, a 1/4" 6*6 steel plate would be just as or less effective than the wood he has under.

How would it be less effective ? We're talking about point loading here
Steve and Myka pretty much covered what I was pointing out
Point loading the concrete floor will break it
By placing a larger foot of something that won't break under the load, you're spreading the weight out over a larger area, thus putting less stress on a smaller area of the concrete
And ya, the wood he has there under the post will collapse under load
Have you ever hammered any soft wood ? It compresses very easily
His wood will compress and/or split

[Myka]

Originally Posted by AquaticFinatic

So I should just build another wall instead of the posts? From what I can find out the floor is at least 4" thick plus. I know I should have run joists and maybe tripled up but to much wiring and plumbing in the way for that.

That is typical slab thickness. The best thing you could do would be to jackhammer that slab out where you want the jack posts and pour a footing under it then hide the jack posts in a wall or something. I imagine you're not keen on that though. The length of a wall spreads the point load of the jack posts provided your bottom plate in the wall is at least doubled to help spread the weight instead of just bending. If you were really concerned, you could build a lintel (like over a window) made with a couple 2x10s to lay on the floor to spread the weight. That won't bend.

[gregzz4]

Just an example of spreading out a load



Figure 7. Bearing pressure on a shallow foundation.

The suggested idea of building a closet is a great plan. Build a load-bearing wall and enclose it to create a storage area. Then the area is not wasted by a jack post

[gregzz4]

Originally Posted by Myka

The best thing you could do would be to jackhammer that slab out where you want the jack posts and pour a footing under it then hide the jack posts in a wall or something

This is, of course, the best solution
Then build a storage room around it

[Jeff000]

Originally Posted by gregzz4

How would it be less effective ? We're talking about point loading here
Steve and Myka pretty much covered what I was pointing out
Point loading the concrete floor will break it
By placing a larger foot of something that won't break under the load, you're spreading the weight out over a larger area, thus putting less stress on a smaller area of the concrete
And ya, the wood he has there under the post will collapse under load
Have you ever hammered any soft wood ? It compresses very easily
His wood will compress and/or split

His 2x6 will be fine. I put 20,000kg buildings on standard 2x6 lumber without the wood having much compression.
Remember a hammer can easily hit with 600 psi.
1/4" steel is not very rigid, it's probably not spreading the weight much farther than an inch past the foot of the pole.


His tank and stuff is at max 3200 lbs. Even if 100% of that weight was on the two stands that is only 1600 lbs a leg. That's about 100psi per post on the concrete with just the 4x4 bottom of the post.

Even a poor concrete basement is at least 1500psi concrete. And then the fact that the concrete itself is spreading the weight to the earth under it. Unless you built on a swamp or think there might be erosion under the slab.

So even if the posts are in a bad spot with only 3" of concrete there still wouldn't be a problem.

And remember the squash blocks to the foundation wall are taking probably at least 35% of the weight, And even at a 16' span with the joists those could take another 35% of the weight without blinking.

[Jeff000]

Originally Posted by gregzz4

Just an example of spreading out a load



Figure 7. Bearing pressure on a shallow foundation.

The suggested idea of building a closet is a great plan. Build a load-bearing wall and enclose it to create a storage area. Then the area is not wasted by a jack post

Your image is only really true if that horizontal part is 100% rigid. The farther you get from the point load the less weight it is carrying. How much weight depends on how much the material you use flexes.


Building a little closet or a stub wall in the center will be more than enough.

[gregzz4]

Originally Posted by Jeff000

Your image is only really true if that horizontal part is 100% rigid

Without ruining this thread, I'll point out that what you've said contradicts what you said previously and supports what I was trying to say

Maybe you misunderstood me when I was talking about where to place the 1/4" steel

[Jeff000]

Originally Posted by gregzz4

Without ruining this thread, I'll point out that what you've said contradicts what you said previously and supports what I was trying to say

Maybe you misunderstood me when I was talking about where to place the 1/4" steel

Under the foot of the post, instead of the 2x6 he has.
I never said his 2x6 will transfer the weight to the large piece of wood he is using.
I simply said the wood and the 1/4" steel would displace the weight to a similar footprint. There will probably be some compression of the 2x6 if that wall is actually taking much weight at all, but once it does a slight turn of the jack will fix that right up.


A single stub wall in the center will carry the weight just fine. A closet in that spot would be great too.
But at the same time, nothing at all would probably never have an issue too. But a little over engineering is seldom a bad thing.

[gregzz4]

Originally Posted by Jeff000

Under the foot of the post, instead of the 2x6 he has.
I never said his 2x6 will transfer the weight to the large piece of wood he is using.
I simply said the wood and the 1/4" steel would displace the weight to a similar footprint. There will probably be some compression of the 2x6 if that wall is actually taking much weight at all, but once it does a slight turn of the jack will fix that right up.


A single stub wall in the center will carry the weight just fine. A closet in that spot would be great too.
But at the same time, nothing at all would probably never have an issue too. But a little over engineering is seldom a bad thing.

Maybe we're not getting the same impression from his photos

I see a small piece of plywood under his jack post. If it's larger, that would explain me talking about a larger plate of steel
If it's a length of 2x6, it's still not sufficient. Either way it will compress and would be better suited with something to spread the load out farther, away from the post, to alleviate any stress on the floor directly under the post

I agree with you saying he could just adjust the post as the wood compresses, but that's not a 'safe' method. As I said, the wood could also split, and then the whole thing is useless

I'm unclear with your statement;
"I simply said the wood and the 1/4" steel would displace the weight to a similar footprint"
I was talking about placing a large plate of steel under the jack post to spread out the load. I never mentioned any wood in my idea

What do you mean ?

[kien]