concrete deck blocks needed?

Old 05-05-16, 01:37 AM
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concrete deck blocks needed?

I own several apartment buildings in Maine and one has a big roofed porch (12x24 give or take) that had some rotted joists. My maintenance man repaired it and replaced the upright supports (ground to deck) with 6 x 6 pt timbers but instead of putting concrete blocks underneath he simply dug down 32" and placed them in the ground. He did say there was an existing piece of PT 2x10 or some such lumber under the original post so he left that.

I am a complete layman but common sense tells me you need to have a concrete block under the posts because otherwise all that weight from the deck and roof is focused on a 36 square inch area (6"x6" post footprint) and it will force that post deeper, resulting in eventual sagging. Whereas a 12"x12" block for example, will spread that weight out over 144 square inches.

He seems to think his 'depth vs width' method is ok. I just want to be sure. Any thoughts you have would be helpful.

thank you!
Old 05-05-16, 02:10 AM
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The posts should have a footer that is down to the frost line. That prevents any movement from frost heave. I'm not crazy about either embedding the posts in concrete or burying them in the dirt. They will last longer if they are set above the ground on concrete [or block] that is supported by a proper footer. Sonotubes are often used for this.
Old 05-05-16, 02:44 AM
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I agree with Mark, he should have dug holes to the frost line depth, inserted 12" diameter sonotubes and filled it with concrete, placing a post base to raise the post off the concrete, thereby eliminating side sway, vertical heave, and keeping the post from being in moisture.

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