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I am planning to extend my deck, which uses pier blocks as below photo

enter image description here

I cannot tell what's underneath this pier block because it was just dirt. There was no pour concrete for certain.

So my question is: if I extend my deck and use the pier blocks, do I need to prepare the ground with anything special? I live in Seattle area. My plan to just dig about 1 foot deep and lay 4-5 inches of aggregate 5/8" minus like from http://www.pacifictopsoils.com/products_all.htm and the pack it.

My neighbor did the same and his last for years. I just want to check for your opinion!?

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  • If the old piers were going to sink, they'd probably already done so. Not true for the new ones, though, so you might want to do them right so that you don't get the new deck portion settling more than the old.
    – Daniel Griscom
    Apr 29, 2016 at 11:37
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    It is hard to say how deep to dig down. When houses are built the contractor levels the ground and fills in shallow spots (much of the time). The trick is to dig down below the top soil it may be deeper. I usually find 6-8" gets me below the top soil but there have been a few that were closer to 18". I back fill the hole with crushed quarry and pack it so there is close to 1/2 the pier block above the ground level (home owner inspection flags if the post are within 6" of earth ). I live in Oregon so your inspection rules may be different. don't use crushed river rock as it really never locks
    – Ed Beal
    Apr 29, 2016 at 13:05

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As requested,,,,It is hard to say how deep to dig down. When houses are built the contractor levels the ground and fills in shallow spots (much of the time). The trick is to dig down below the top soil it may be deeper. I usually find 6-8" gets me below the top soil but there have been a few that were closer to 18". I back fill the hole with crushed quarry and pack it so there is close to 1/2 the pier block above the ground level (home owner inspection flags if the post are within 6" of earth ). I live in Oregon so your inspection rules may be different. don't use crushed river rock as it really never locks – Ed Beal Apr 29 at 13:05 delete

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