Can I pour a concrete pad (below grade) for a retaining wall?

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Old 06-14-16, 05:58 PM
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Can I pour a concrete pad (below grade) for a retaining wall?

I'm building a 2' high retaining wall parallel to the house about 7' out from the house. Behind the wall will be built up a driveway, which will get paved. I understand that the base of the retaining wall should be below grade and conventionally would be compacted stone, topped with sand.

But my excavator suggests pouring a 4" deep concrete pad the length and width of the wall and laying the first layer of blocks on that. He thinks that will be easier to make level and provide a firmer base. The grade slopes slightly so there will need to be a couple of steps down along the wall.

I've never heard of doing it this way. Any opinions? Or better yet, experiences?
 
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Old 06-14-16, 06:31 PM
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In your area you need a footing pored below the frost line for a retaining wall.
 
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Old 06-14-16, 07:29 PM
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Actually, if it's dry laid, not mortared, I don't need a footing below frost line.
 
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Old 06-15-16, 03:56 AM
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A concrete footer should always be poured down to the frost line. Any freeze/thaw cycles will affect solid concrete more than compacted stone.
 
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Old 06-15-16, 05:41 AM
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Actually, if it's dry laid, not mortared, I don't need a footing below frost line.
That reads to me as if you have already made up your mind so why are you asking us?
 
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Old 06-17-16, 01:32 PM
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Unless you're going below the frost line, a concrete footer is probably going to do more harm than it does good. Also one that is only 4" isn't going to help at all anyway. Just put on a good gravel footer like recommended by the manufacturers of retaining wall blocks. It's easier, cheaper and works better.
 
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Old 06-17-16, 07:26 PM
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If you set the retaining wall block on a concrete slad or footing, you are not following the specific installation specifications. The retaining walls are designed to not be used on a rigid concrete footing. - A compacted gravel base is specifically recommended by every system I have seen.

I saw a segmental retaining wall along that was 2' to 40' high and 400' long. It looked pretty good when I saw it about 15 years after construction.

Dick
 
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