Is this good enough for support??

[sphelps]

Yeah point loading slab = bad. That's why structural engineers cringe but it'll probably be fine if that helps as it's really not that much weight. Personally would have build a wall in place of the beam and shimed it up tight under the joists to distribute the load.

[Myka]

Originally Posted by sphelps

Personally would have build a wall in place of the beam and shimed it up tight under the joists to distribute the load.

That's a good idea. You could build yourself a little "load bearing" closet right there.

[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.

[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

[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

[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.