Concrete newbie here.
I am building a concrete pad for an A/C unit in an already excavated area of the yard (new plant bed). The excavated area is around 8" deep. I want to build a 4'x4'x16" concrete block for the air conditioning unit.
Here's a visual :
I understand that these are the steps :
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Excavate slab area by 8" and backfill ~6" with gravel.
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Level & tamp gravel base.
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Build forms and adjust pitch of about 1/4 inch for every 12 feet.
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Mix the concrete and pour into the form.
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Screed and level out concrete surface
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Float & finish surface
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Water cure for a week.
I have a few questions :
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Is this the right approach to building a very thick concrete pad/block ?
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Is the base for this pad sufficient ?
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Should I use rebar mesh to reinforce the block ?
I would have considered building this using pre-cast concrete blocks , but my masonry skills are next to nothing and I felt that pouring a block is easier than laying courses of concrete blocks.
Best Answer
I think the better approach is to build a thicker gravel base, and use less concrete for the pad. Backfill with gravel, in layers, compacting between each 4"-6" layer.
I'm not sure you're aware of how much concrete you'll need for your proposed 12" thick pad. See this: http://www.calculator.net/concrete-calculator.html. Your 4'x4'x12" pad will use 27 bags of concrete, nearly a ton, if buying pre-mixed. I think building a thicker base, and then pouring a 4" or 6" concrete pad, with some rebar mesh, is a better/easier approach.
Your plan is solid, but I'd add several things to is: