Jon
Are you talking about a growing on tank or a main pond build?
If it's a growing on tank that's being built on a concrete substrate (as I understand is the case) and the concrete you've poured is "firm" i.e. you can walk on it without sinking into it, then I reckon it's probably good enough to fibreglass onto.
If it is firm, I'd think the most you'll need to do is cut around the edges of the new concrete slab to ensure you've got a sound footing to build the block walls on.
Remember, lots of people use foam to insulate their tanks/ponds, fibreglass directly over it and never have any problems!
Think carefully about what you need to do to achieve what you want before you go digging it all up!
Good Luck
Bob
Uncured Concrete
Moderators: B.Scott, vippymini, Gazza, Manky Sanke
Hi Bob
Yes it is a growing on pond - approx 1000 gals so about 8 tons of water to be supported. I can walk on it; I can even jump up and down on it in a rage!
My reason for digging up was because I felt that the pad wouldn't be a good substrate for building the walls. Because I've laid an outer course of 18 inch hollows (also filled with s**t that hasn't set) to contain the pad and add some lateral support to stop the entire pad moving I will have to build on the new pad. The only other option would be create a trench around the perimeter of the pad and laying a new footing which could then be built on. I think it might be simpler just to pull the whole lot up and start again.
Cheers
Jon
Yes it is a growing on pond - approx 1000 gals so about 8 tons of water to be supported. I can walk on it; I can even jump up and down on it in a rage!
My reason for digging up was because I felt that the pad wouldn't be a good substrate for building the walls. Because I've laid an outer course of 18 inch hollows (also filled with s**t that hasn't set) to contain the pad and add some lateral support to stop the entire pad moving I will have to build on the new pad. The only other option would be create a trench around the perimeter of the pad and laying a new footing which could then be built on. I think it might be simpler just to pull the whole lot up and start again.
Cheers
Jon
Hi Jon
Pity you are so far away…
I'm not convinced you need to hack out the pad Jon
The pad is effectively only a fill to set the bottom drains in?
From what I can see you laid hollow blocks onto the original concrete floor? Were these laid with a decent mix?
Presume you were intending to lay the 9" solids on edge onto the hollows to form a 4" thick wall?
Regards
Dave
Pity you are so far away…
I'm not convinced you need to hack out the pad Jon
The pad is effectively only a fill to set the bottom drains in?
From what I can see you laid hollow blocks onto the original concrete floor? Were these laid with a decent mix?
Presume you were intending to lay the 9" solids on edge onto the hollows to form a 4" thick wall?
Regards
Dave
Hi Jon
If your 9" blocks are set straight onto the original concrete substrate I don't think you have any worries - providing the mix you used to set the blocks on was OK and has set properly
If you used a good mix to set the blocks, just carry on with the build. If not, lift the blocks, clear the soft cement mix from under them and then just relay them on a good mortar mix - but I still don't think you need to take the whole new base up!
1000 gallons is about 4.5 tons of water - but the weight is spread over the whole of the base. The actual pressure per square inch is directly proportional to the depth of the water - but is unlikely to be excessive IMO.
If you want to do something extra "just in case", you could lay another row of blocks alongside the existing ones (on the outside to make a sort of step around the edge) - making sure you use a good mortar mix
Fill the gap between the two rows and I'm pretty certain your the walls of your tank wont go anywhere! And much less hassle than digging up what you've done. 
Bob
If your 9" blocks are set straight onto the original concrete substrate I don't think you have any worries - providing the mix you used to set the blocks on was OK and has set properly
If you used a good mix to set the blocks, just carry on with the build. If not, lift the blocks, clear the soft cement mix from under them and then just relay them on a good mortar mix - but I still don't think you need to take the whole new base up!
1000 gallons is about 4.5 tons of water - but the weight is spread over the whole of the base. The actual pressure per square inch is directly proportional to the depth of the water - but is unlikely to be excessive IMO.
If you want to do something extra "just in case", you could lay another row of blocks alongside the existing ones (on the outside to make a sort of step around the edge) - making sure you use a good mortar mix
Fill the gap between the two rows and I'm pretty certain your the walls of your tank wont go anywhere! And much less hassle than digging up what you've done. Bob
Hi Dave and Bob
I thought that a reinforced pad with a minimum of a C20 mix was essential to ensure that cracking wouldn't occur and that if there was significant cracking that this could have dire consequences for the fibreglass.
I had a go at the pad with my SDSPlus drill with a chisel bit. I dont actually need to fire it up - I can remove material just by digging the bit into the pad! It is firm enough to walk on but I would have thought that once the weight of the water is applied it would move. Otherwise wouldn't it be sufficient to tamp down a load of hardcore and forget about using reinforced concrete?
I hadn't intended to build over the hollow blocks - these were merely containment for the pad and to provide additonal lateral support. I not entirely sure how thick the pad is in the middle of the shed - where the walls are laid it is 12 inches but given that this is a farm building it could be a lot less in the middle! Also the pond would be considerably bigger if I went with this (tempting - but I would need to build a much more substantial structure to accomodate the additional pressure).
I was going for a depth of 3 foot so I agree that there wouldn't be that much pressure (I think about 3lbs per square inch) at the base. I was going to lay the first few course of 4" dense blocks on their side for additional support then build upright higher up the wall where there is less pressure.
The mortar mix for the blocks was fine - I mixed this myself very precisely because I have never done any building work before and it has set rock hard.
At the moment I'm tempted to not only dig up the pad but to keep going downwards and cut into the existing base so that the pond is only partially raised. This would mean I won't have to worry about the structural integrity of the original pad. I might change my mind after trying to dig it all up!
Cheers
Jon
I thought that a reinforced pad with a minimum of a C20 mix was essential to ensure that cracking wouldn't occur and that if there was significant cracking that this could have dire consequences for the fibreglass.
I had a go at the pad with my SDSPlus drill with a chisel bit. I dont actually need to fire it up - I can remove material just by digging the bit into the pad! It is firm enough to walk on but I would have thought that once the weight of the water is applied it would move. Otherwise wouldn't it be sufficient to tamp down a load of hardcore and forget about using reinforced concrete?
I hadn't intended to build over the hollow blocks - these were merely containment for the pad and to provide additonal lateral support. I not entirely sure how thick the pad is in the middle of the shed - where the walls are laid it is 12 inches but given that this is a farm building it could be a lot less in the middle! Also the pond would be considerably bigger if I went with this (tempting - but I would need to build a much more substantial structure to accomodate the additional pressure).
I was going for a depth of 3 foot so I agree that there wouldn't be that much pressure (I think about 3lbs per square inch) at the base. I was going to lay the first few course of 4" dense blocks on their side for additional support then build upright higher up the wall where there is less pressure.
The mortar mix for the blocks was fine - I mixed this myself very precisely because I have never done any building work before and it has set rock hard.
At the moment I'm tempted to not only dig up the pad but to keep going downwards and cut into the existing base so that the pond is only partially raised. This would mean I won't have to worry about the structural integrity of the original pad. I might change my mind after trying to dig it all up!
Cheers
Jon
Wooaaaah!
The original concrete base has (presumably) been down for a few years and the ground below will be compacted and stable - it is therefore unlikely that it will move anywhere. Start digging up the original base and disturbing the ground beneath it and you are likely to unsettle the whole area.
When you refer to just using compacted hardcore, this would be theoretically possible in the right ground conditions.
I know one pond that has been dug into solid chalk. The dig was "benched towards the botom drain and the pipe from it was accommodated in a channel and surrounded in concrete. Chicken wire was laid on the chalk to act a a key for the render which was appliwed directly to the chalk. The render was then fibreglassed and there have been no problems so far.
Had the ground been clay or sandy soil, this method could not have been used as the ground would be much more likely to move.
Keep to your plans and build off the blocks you've laid - and be thankful that the original concrete base has saved you having to dig it all up.
But learn from the mistake and make sure you use the correct concrete mix when you do your main pond.
Cheers
Bob
The original concrete base has (presumably) been down for a few years and the ground below will be compacted and stable - it is therefore unlikely that it will move anywhere. Start digging up the original base and disturbing the ground beneath it and you are likely to unsettle the whole area.
When you refer to just using compacted hardcore, this would be theoretically possible in the right ground conditions.
I know one pond that has been dug into solid chalk. The dig was "benched towards the botom drain and the pipe from it was accommodated in a channel and surrounded in concrete. Chicken wire was laid on the chalk to act a a key for the render which was appliwed directly to the chalk. The render was then fibreglassed and there have been no problems so far.
Had the ground been clay or sandy soil, this method could not have been used as the ground would be much more likely to move.
Keep to your plans and build off the blocks you've laid - and be thankful that the original concrete base has saved you having to dig it all up.
But learn from the mistake and make sure you use the correct concrete mix when you do your main pond.
Cheers
Bob
Jon,
I can see that your concerns arise from doubts on the integrity of the original slab.
Suspect you may have made up your mind already…
At the end of the day you need to be comfortable with the build, I suspect you may be rather over engineering it but at the end of the day you need to do what you are comfortable with.
Regards
Dave
I can see that your concerns arise from doubts on the integrity of the original slab.
Suspect you may have made up your mind already…
At the end of the day you need to be comfortable with the build, I suspect you may be rather over engineering it but at the end of the day you need to do what you are comfortable with.
Regards
Dave
Hi Bob
Without digging down I think the foundation is red sandstone. I live on top of a hill where after only a few inches of soil you generally hit rock! Therefore I would imagine that the original concrete base is sitting on pretty secure foundations. I reckon you're right about being able to build directly off the original floor. Laughable in light of recent events, the reason I was keen to lay a pad was because I wanted to do things "properly"!
Have you seen the pond build at Coldwater Collection? Ken is building a 250,000 gallon growing on pond which is a nine foot deep basin where chicken wire has been rucked-up with pegs, rendered and fibreglassed. I've got say that to me it looked incredibly flimsy, but everone seemed very confident that it would work. The day I was there they were laying the first piece of fibreglass - looked like a year's worth of work to me!
The mian lesson I have learned is to either do things myself or supervise very closely the critical elements. Because my neighbours were putting themselves out to help me and I thought had some experience I didn't pay too much attention to the mixing. I've spent some of this afternoon trying to work out how to dig everything up and put it right without my neighbours finding out - they will be mortally embarassed once they know what has happened.
Cheers
Jon
Without digging down I think the foundation is red sandstone. I live on top of a hill where after only a few inches of soil you generally hit rock! Therefore I would imagine that the original concrete base is sitting on pretty secure foundations. I reckon you're right about being able to build directly off the original floor. Laughable in light of recent events, the reason I was keen to lay a pad was because I wanted to do things "properly"!
Have you seen the pond build at Coldwater Collection? Ken is building a 250,000 gallon growing on pond which is a nine foot deep basin where chicken wire has been rucked-up with pegs, rendered and fibreglassed. I've got say that to me it looked incredibly flimsy, but everone seemed very confident that it would work. The day I was there they were laying the first piece of fibreglass - looked like a year's worth of work to me!
The mian lesson I have learned is to either do things myself or supervise very closely the critical elements. Because my neighbours were putting themselves out to help me and I thought had some experience I didn't pay too much attention to the mixing. I've spent some of this afternoon trying to work out how to dig everything up and put it right without my neighbours finding out - they will be mortally embarassed once they know what has happened.
Cheers
Jon