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View Full Version : Footer size and block placement



Dave Starr
08-09-2008, 12:52 PM
Barring a deluge, I hope to be ready for footers in a week or 2. Would 6x12 footers be ok, or should I go with 8x16? Walls will be 6 or 7 courses, haven't decided yet. Also, if 6x12 footings will work, can I put the blocks 1" back from the inner edge, leaving 3" on the outside?

wputnam
08-09-2008, 02:22 PM
Placement of block on the footer should not be a concern.. Unless, this pond was going to be a totally free standing pond or you had concerns of using it as a retaining wall for a hill on one side of the pond...

6 x 12 is fine... As long as you have re-bar in it...

What is your soil conditions like?
Are you going to pour a slab on the inside?
Are you going to use a liner or coat the block?

Dave Starr
08-09-2008, 03:27 PM
Placement of block on the footer should not be a concern.. Unless, this pond was going to be a totally free standing pond or you had concerns of using it as a retaining wall for a hill on one side of the pond...

6 x 12 is fine... As long as you have re-bar in it...

What is your soil conditions like?
Are you going to pour a slab on the inside?
Are you going to use a liner or coat the block?

The bottom of the hole is rock hard bluish clay.
No slab, just a footer for the walls.
Liner pond.

Rebar - I'm thinking 3 runs 3" apart & centered in the footer.

wputnam
08-09-2008, 03:40 PM
Excellent re-bar.. And you'll have vertical re-bar through the block cells with an L bend possibly at the bottom of the vertical re-bar.. L bend Not required, yet adds...

For the liner... If you don't know what a hospital corner is, consider asking someone to show you how to make one... Do this with the liner in the corners if your pond is going to be having square corners...

1Kflyerguy
10-02-2008, 08:52 AM
Is there any sort of guideline on thick to make a footer for a block wall? Seems like there is wide variation in what people do, I have seen a few books that say no footer needed, while others on this board have pourer 4, 6 or even 8 inch thick footers?

I am trying to figure out how big I need to go for my pond, which is 9 by 14, 4 feet deep, concrete block construction.

I plan to add rebar to footer and walls. I live in Northern Ca, and we we don't freeze, so I don't have to deal with that. Of course it does shake every once and while.... My soil on the pond bottom is mostly a clay with lots of small rocks, probably leftover from the nearby creek.

Any sugguestions on how thick? Can I get away with 4 inches or do I need 6 inches thick?

mpageler
10-02-2008, 09:42 AM
I think most of us way overbuild our footers. Tendancy is to minic what is done in home construction footings. There, the footings are meant to distribute the massive weight from all the stories above it. In pond contruction, there's way less weight to carry from 5 tp 10 coarses of blocks. I thiink there's also a tendancy to put large footers for frost heaving but if the footer's are below the freeze depth, what heaving can you resonably expect? Depending on the soil type, the shrinking and swelling of the soil will have more impact on the wall structure than freeze heaving. Clay soils for example have a high shrink/sweell capability and can exert tremendous force on structures.

There is a reputable koi pond build up here in MN that doesn't put in footers and is having no problems. Auntiesue did the same and no problems after 2 winters.


Is there any sort of guideline on thick to make a footer for a block wall? Seems like there is wide variation in what people do, I have seen a few books that say no footer needed, while others on this board have pourer 4, 6 or even 8 inch thick footers?

I am trying to figure out how big I need to go for my pond, which is 9 by 14, 4 feet deep, concrete block construction.

I plan to add rebar to footer and walls. I live in Northern Ca, and we we don't freeze, so I don't have to deal with that. Of course it does shake every once and while.... My soil on the pond bottom is mostly a clay with lots of small rocks, probably leftover from the nearby creek.

Any sugguestions on how thick? Can I get away with 4 inches or do I need 6 inches thick?

1Kflyerguy
10-02-2008, 12:18 PM
Clay soils for example have a high shrink/sweell capability and can exert tremendous force on structures.

There is a reputable koi pond build up here in MN that doesn't put in footers and is having no problems. Auntiesue did the same and no problems after 2 winters.

I am aware of the shrink/swell properties with clay soil. To a certain extent whole houses can move slightly due to the changes in clay soil. Would a footer help everything move as a unit, or if the blocks are cemented and reinforced with rebar they will probably move as a unit anyway...

I have the tendency to overbuild things, and while I want to be safe and build a solid pond, I was also looking to minimize the amount of concrete I need to move, mix and pour..... I am not as young as I used to be.

Ponddigs
10-02-2008, 12:26 PM
Is there any sort of guideline on thick to make a footer for a block wall? Seems like there is wide variation in what people do, I have seen a few books that say no footer needed, while others on this board have pourer 4, 6 or even 8 inch thick footers?

I am trying to figure out how big I need to go for my pond, which is 9 by 14, 4 feet deep, concrete block construction.

I plan to add rebar to footer and walls. I live in Northern Ca, and we we don't freeze, so I don't have to deal with that. Of course it does shake every once and while.... My soil on the pond bottom is mostly a clay with lots of small rocks, probably leftover from the nearby creek.

Any sugguestions on how thick? Can I get away with 4 inches or do I need 6 inches thick?


You can find these type guide lines at RCP online.

http://www.rcpblock.com/images/support/pdf/221.pdf

Its pretty easy just match up numbers on height and it will give a idea........maybe a little over kill for a pond. But better safe the sorry when your in clay. By adding footings and suggested steel layout I have had no problem with a few shakers or clay.Also you can pour floor at same time and tie steel togather from side to side. Then you can add your block, pour cells, seal or liner over....................don't forget your bottom drains in pouring of floor and Tpr's can be added in block.

Hope this helps............................

majederr
10-06-2008, 09:33 PM
Our contractor made our footers 10" x 20" for both our pond (10 x 20 x 7.5) and filter house (5 x 5 x 25).