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RE: Granite Step Foundation

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It depends. 
If he is placing the concrete on grade and then placing the gravel on the concrete, and then the granite on the gravel; he may be using the concrete to avoid the gravel settling into the subsoil.  It would be about the same as using a geotech fabric. 
But from what you are presenting, he intends to place gravel on grade then the concrete, and then the granite paver.  If the paver is placed on the concrete while plastic, it would be similar to increasing the paver thickness by the thickness of the concrete. 
The only way to reduce settling would be to increase the depth to a lower bearing strata, and/or increase the plan dimensions to reduce the bearing pressure.  I don't know where this is geographically, but the other issue is movement from freeze thaw of the subgrade.  Freeze thaw issues would drive you to increaseing the base thickness using open graded grushed rock.   

Regards, Harold Sprague

To: seaint(--nospam--at)
From: wcmiller(--nospam--at)
Subject: Granite Step Foundation
Date: Tue, 28 Jun 2011 17:29:33 +0000

I am having a paver patio installed by a contractor and he will be using a 8" compacted gravel foundation to support the pavers. Additionally, a single granite step (48"x18"x7") will be installed. The contractor says he needs to pour a 6" concrete foundation with the same footprint as the step in order to prevent the step from settling over time due to the weight of the step. However, I think the step should be placed directly on the 8" compacted gravel foundation. Do any of you think the concrete pad is necessary?


Chris Miller, P.E.