Thin concrete floor, Pour pad?

I was a foreman in all forms of concrete construction for over thirty years. A 300 gallon tank is going to weigh around 2600-2800 pounds. A 8x4 pad is 32 sq. ft. That is less than 100 pounds per sq. ft. Go into the basement and stand with your feet together and you are applying more pressure than that. A tank of water is dead weight. It is not a piece of machinery that is going to vibrate and move and create lateral movement. Your floor is 120 years old. If you dig it up you will only loosen what has settled. A 4 inch pad on top of the floor with 1/2 inch bar @ 12 inch center would be overkill, especially with a wooden stand.
 
i was a foreman in all forms of concrete construction for over thirty years. A 300 gallon tank is going to weigh around 2600-2800 pounds. A 8x4 pad is 32 sq. Ft. That is less than 100 pounds per sq. Ft. Go into the basement and stand with your feet together and you are applying more pressure than that. A tank of water is dead weight. It is not a piece of machinery that is going to vibrate and move and create lateral movement. Your floor is 120 years old. If you dig it up you will only loosen what has settled. A 4 inch pad on top of the floor with 1/2 inch bar @ 12 inch center would be overkill, especially with a wooden stand.


+1
 
My basement pad is 4 inches with some french drains running in some areas (I called the builders). I have a 7ft by 14 ft by 45 inch deep endless pool on it. That comes to about 245 lbs per square foot with the water in it.

Jump up and down over the area where the stand is to be placed Your jumping will put more pressure on the concrete than what I have. The ground is also compacted under that concrete to add even more support

LEAVE THE FLOOR ALONE AND SAVE YOUR MONEY!
 
LOL. Over engineering is the sign of inferior engineering.

I agree 100% with laga77.

If your so concerned just drill a few small test holes in the area where the tank will be and if it's not concrete directly on hard dirt then maybe consider adding to the pad. Rebar is beyond overkill and 3 inches is all you would need MAX. If the 1inch pad is directly backed up by dirt that hasn't settled away from it in over 120 years the weight of your tank won't move it.

Oh yea... Be sure to fill your test holes with hydraulic cement
 
Wouldn't it be more likely that the basement was rubble stone for the first 100 years and then some diy dude slapped an inch of concrete down in the last few when they finished it?

Seems weird to assume the floor's 120 years old, and then say it's prolly sturdy since it hasn't moved in all that time.. I didn't think that pouring an inch of concrete over dirt was a common practice in the 1800's
 
Your right that math is acurate, however the size pad you originally suggested and I agree with was an 8'x4' which equals 32 sq.ft.. This would be double your math here which would equal 56 bags.


Ok. I see now. Thx. I did mean to calculate 8x4 instead of 8x2.
 
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The floor was likely just dirt and it's likely hard packed dirt that is 120 years old. And your right. Someone in the last 50-60 probably had it poured. The point being that the dirt under the concrete is going to be exceptionally hard and not going to move.

And for all you know the tank is going in an area where the dirt was the lowest and there is 4" of concrete a ready there. Drill test holes.
 
Wouldn't it be more likely that the basement was rubble stone for the first 100 years and then some diy dude slapped an inch of concrete down in the last few when they finished it?

Seems weird to assume the floor's 120 years old, and then say it's prolly sturdy since it hasn't moved in all that time.. I didn't think that pouring an inch of concrete over dirt was a common practice in the 1800's

I can almost guarentee that, it's called a slush coat, we pour them in crawl spaces for convenience for homeowner so they don't have to walk or work on dirt or stone. All we do is pour and screed out nothing more.1=2"
 
There is definitely not need to drill test as we broke through this space awhile ago to replace the sewer pipe. Basically where the middle of the tank would sit be broke open a space 1.5' wide. His pipe ran the whole length of the basement and we didn't see any concrete thicker than 2"
 
It is very wet almost clay like dirt but the area I was working in isn't the best example as it was dug out twice. Once to lay original sewer pipe then recently to replace it. The soil is super moist we even had parts of the hole pool with water when we dug it out
 
It would be better if the stand actually spread the weight evenly over the whole 8x4, but since it's not a solid block of wood, isn't it more like the weight would be borne by the vertical braces of the stand? So, say 4 corners and 2 extra supports on the front and back, that's a pretty sturdy stand, and it's 8 legs, so 700lbs on each "leg." For me, seeing water pool is a bit scary. Does it ever flood?

A concrete pad on top wouldn't be the perfect solution, but if you can't dig the floor up again, it would spread that point load out to the 100 lbs mentioned. I would do something under the tank to spread the weight. If not a concrete pad, then maybe work support joists into the stand to do the same.
 
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A pickup truck weighs between 5,000lbs and 6,000lbs, that's about 1,500lbs per square foot on your 3.5" thick driveway.

I would not bother. You're thinking into it too much. imo
 
That's what I was thinking originally when I made this post. Pour a pad and build a wood stand with a bottom frame to try to spread the load as much as possible over the entire pad.
 
That's what I was thinking originally when I made this post. Pour a pad and build a wood stand with a bottom frame to try to spread the load as much as possible over the entire pad.

Yeah, I fixed it. Quoted the wrong one.
Another plus is maybe you could use self-leveling for the top part of the pad? That would make the install easy.
 
Your just adding more weight to the area in question. Adding it to the top only makes it worse from a structural point of view.

If you want to spread the load out your going to just need a bigger stand with large feet.
 
Your just adding more weight to the area in question. Adding it to the top only makes it worse from a structural point of view.

If you want to spread the load out your going to just need a bigger stand with large feet.


I'm sorry it's hard to understand which way your suggesting I go reading your posts. This tank will have large post feet. Honestly I was thinking of using 4x4 or 6x6 wood to make a square frame to lay on floor then attach at least 6 posts on top of that and then the actual top assembly. This should distribute the weight of the tank over the entire footprint of the tank.
 
If you build the stand like that I can't imagine you would have any problems. 4x4 would be plenty. Only problem is they have a tendancy to twist with age so there is that problem as well. Cedar posts are an option but a pricy one.

What you need to do is honistly calculate the total weight of your stand and the total square inches of your contact with the floor. Once you have that figured out you can honistly decide if you have enough strength in the concrete. You might honistly be fine using 2x4s to build the stand but build a base from 4x4s and plywood so you have the smallest amount of psi under the stand possible.
 
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