Cincerblock and concrete

There are so many concerns I see and the dynamics of it all make it difficult to address each. There has been some good points made too which should be considered. I highly recommend getting an engineer involved. You don't need to spend an arm and a leg on it either. IMO it will be money well spent and piece of mind. For starters, I highly doubt cinderblocks will work they are so weak although you might get away with them with concrete filled n dowelled cores, a better choice would be a concrete block - yes there is a difference. There are even different types (weight) within conc. block, your need dictated by bond, reinf., loads etc.. My first thought would be however why deal south either, stay with me here.... The slab, I'm not sure why you want to entertain post tension in this application, it would be an added costs whereas you could put that money into the engineer fees. With an engineer involved you might be looking at something as simple as an isolated thickened matt slab with integrated upturned/inverted beams serving not only as the reinforcement for the imposed loads but doubling as a kneewall and eliminating the block all together. Food for thought, I do hope you involve an engineer. Gluck

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I agree with clowning around. Post tensioned would be unnecessary. A 12 inch thick reinforced slab is what you would want under the tank. It should have an expansion joint between it and the surrounding slab and building foundation. The walls of the holding tank should be concrete, not block. The reinforcing should go from the foundation into the walls, just like your house. I am sure this would need a building permit, and therefore an architect and engineer drawings. If not an engineer should design it regardless. His cost will be a minor part of what I imagine this total build will cost. Good luck with the build.
 
Also, just looking at that structure that holds all that water in the air, you would want reinforced concrete columns and beams, as well as a for wed elevated slab that it would sit on. You are definitely in engineer needed territory, but it completely doable.
 
When I started looking into the slab construction, it looked to me that 1000sqft was the break even point in Dallas. At 1200 sqft, the post tension was not more expensive.

Dallas has clay earth which has been known to shift over time and given the weight loading (equivalent to a house) and the square footage (also equivalent to a house), I found that it would be safest to look at this as a foundation instead of a slab.

I terms of stresses.. the water in the sump is 12-18" high. I'm not sure where that is going to topple over cinderblocks. Like I said above.. I've used plywood and build tanks that were much higher. If making this out of plywood works, why would cinderblocks break ?

Getting an engineer - ok.

Saying that 18" of water pressure will break a post tension slab with cinderblock sides ... I just don't see it. Raising concern - I get. But if the feedback doesn't actually help me...

Here's what I have so far:

1. Get an engineer. See if post tension is really needed.
2. Before the foundation is poured, tie vertical rebar up into into the sump corner blocks (or every two feet) or base blocks for the tank or surge.
3. Use masonry adhesive instead of construction Fluegel.
4. Drill into the cinderblock sides and tie them horizontally with rebar and anchor to the vertical rebar from the foundation.
5. Fill in the cinderblocks holes (witg rebar in them) with concrete. The blocks were basically forms.
6. Fill holes and seal with hydraulic cement.
7. Paint with waterproofing drylock

Did I catch everything?
 
If I'd realized how flimsy concrete and rebar was, I may have started with a different medium. :)

For the platforms, I may reconsider using 2x12s and just epoxy the parts underwater.

The flat sections are triple stacked 3/4" plywood.
 
A web elevated slab is a formed elevated slab that was autocorrected.

Block has high compressive strength, a lateral load is only on the bond of the slab to block. I can push over a non reinforced block wall 10 feet high. Water pressure is unrelenting.

Since I am offering no help to you, in the field that I work in, I wish you good luck and.
 
Last edited:
wasn't talking to you specifically, sharp.

I'm adding vertical rebar and filling with concrete to strengthen the vertical structures.

agree that water pressure is unrelenting - but 18" of water pressure shouldn't push over 3 cinderblocks with rebar and concrete that are tied to rebar in the slab.
 
I spoke to a structural engineer this morning. He didn't see it as an intractable problem... basically, he'll look at the loading which is in the middle and determine the amount of additional concrete and support needed there.

I shared the water weight detail and he didn't see it as a problem. Basically, as long as I have an engineered slab, he says it's no issue.
 
I'm not the smartest when it comes to this stuff but I have some concerns
If there is sunlight coming directly down onto the tank you are going to have some major algae issues and considering it's a green house I think you will have some heat problems also as people stated before you will need rebar to go through the floor and up into the cinder blocks and you should probably fill the cinder blocks with concret for extra strength these are just my opinions and I could be totally wrong


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Yes.

Here's what we have so far:

1. Get an engineer. See if post tension is really needed.
2. Before the foundation is poured, tie vertical rebar up into into the sump corner blocks (or every two feet) or base blocks for the tank or surge.
3. Use masonry adhesive instead of construction Fluegel.
4. Drill into the cinderblock sides and tie them horizontally with rebar and anchor to the vertical rebar from the foundation.
5. Fill in the cinderblocks holes (witg rebar in them) with concrete. The blocks were basically forms.
6. Fill holes and seal with hydraulic cement.
7. Paint with waterproofing drylock

Anything not in this list?
 
karimwassef said:
Yes.

Here's what we have so far:

1. Get an engineer. See if post tension is really needed.
2. Before the foundation is poured, tie vertical rebar up into into the sump corner blocks (or every two feet) or base blocks for the tank or surge.
3. Use masonry adhesive instead of construction Fluegel.
4. Drill into the cinderblock sides and tie them horizontally with rebar and anchor to the vertical rebar from the foundation.
5. Fill in the cinderblocks holes (witg rebar in them) with concrete. The blocks were basically forms.
6. Fill holes and seal with hydraulic cement.
7. Paint with waterproofing drylock

Anything not in this list?
Click to expand...


This is a very sound plan ..
 
You mentioned a comparison of plywood to cinderblock, plywood is much stronger in this application (laterally). My 4 year old can push over 3 courses of cinderblock (unreinforced of course)....

The load being applied down will actually help strengthen it laterally but it would still be a concern of mine...

Im glad you've involved an engineer. Stick within his recommendations :) Gluck.

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Strong 4 year old... I stacked 3 blocks today and I couldn't do it without force... no, I'm not a weak guy.

The blocks are going to be glued with masonry adhesive which (if anything like the epoxy I've used to glue blocks together in the past) is stronger than the blocks themselves.

The blocks are also glued into a frame with corners and glued to the foundation. I trust this because I had the distinct displeasure of trying to wreck a concrete tank I built with epoxy and block only... it was nearly unbreakable, untippable, unwedgeable. I literally was in pain until I took a hammer to break it apart.

I understand "discomfort" but I prefer calculations and data. My own experience with blocks is that they're strong when glued into a framework... so the uncertainty in this thread surprises me. So I'll pay $500-$1000 to get it engineered.
 
I just have to say I think this is way to big of a project for a DIYer. You should hire a contractor. Heck, a project this big should have a designer/architect, engineer, contractor. Theres is so many variables.
 
thank you. I'm sure that hiring a professional team would be effective also.

I appreciate the feedback - I'm looking for help on how to do this... not whether I should do it.
 
karimwassef said:
thank you. I'm sure that hiring a professional team would be effective also.

I appreciate the feedback - I'm looking for help on how to do this... not whether I should do it.
Click to expand...

Okay I think we agree then, right?
In my opinion as a journeyman carpenter who has worked with concrete, It is possible, and your design might work well or it might not. The great thing about concrete is you can form it into any shape imaginable. There literally is no limit, you can incorporate curves and other designs into it. I also think mixing the concrete and concrete block will be too much. Just choose one or the other.
 
I will say one thing that is going to be one h ll of a tank. Do you plan to have some furniture or something in that small building? I would want to make it a place where you are going to hangout. Maybe put a TV ect. I would not do a green house because of the heat. Just some non design things to think of. Post pictures when it is done.
 
ph_ said:
Okay I think we agree then, right?
In my opinion as a journeyman carpenter who has worked with concrete, It is possible, and your design might work well or it might not. The great thing about concrete is you can form it into any shape imaginable. There literally is no limit, you can incorporate curves and other designs into it. I also think mixing the concrete and concrete block will be too much. Just choose one or the other.
Click to expand...

Paying a lot of money can make things better. I agree :)

I'm using concrete in the hopes that it's easier and cheaper. If there are better options, I'm open to redesign.

I haven't heard any concerns on mixing block and formed concrete... why would this be?
 
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