Fill around support posts - dirt or rock?

ramatsuAugust 13, 2009

I'm replacing some rotten support posts under our mudroom (formerly a porch, that someone enclosed years ago), which sits 3-4' above ground. After I've replaced the supports we will be regrading the yard, filling in that area 3-4' deep and covering the new posts.

http://gallery.me.com/ramatsu#100123...&bgcolor=black

1) I'm pouring footings on top of untouched ground, but I'm concerned about lateral support from the fill. I won't have room to get a compactor around the posts underneath the mudroom. Should I fill that area with gravel or other rock-based product for sufficient lateral support?

2) I'm torn between pressure treated posts (attached to galvanized saddles set in the footers) vs. concrete tube pillars. I'm not a big fan of creating problems for someone 20 years down the road when the pressure treated posts need to be replaced. If the answer to question 1 is "use gravel or rock," digging out those posts could be a real nightmare. But the tube pillars are more work and money.

Any thoughts would be very welcome!

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maryland_irisman

I admire the thought you have given what you are planning to do and surely wish I could be more positive on the wooden posts.

Without adequately compacting, neither dirt nor rocks will give lateral support. The pressure treated posts if used should be rated for ground contact. Not all pressure treated wood has that rating.

Would the wooden posts conform to local codes? I'm assuming a permit isn't pulled since, at least in my area, the support means would be spelled out and subject to approval. Anything 3' or over would require approval also, any buried lumber would not be an acceptable means of support on a permanent structure.

From vibration and movement during use and depending on the type of soil, the dirt will either compact itself or open the hole to the point there is no soil contact on the posts (clay soil for example).

    Bookmark   August 13, 2009 at 7:49PM
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alphonse

Just a suggestion.
If allowed by AHJ, think about steel posts-pipe- plenty of support, if wrapped with suitable product, corrosion wouldn't be a problem 'til you've mouldered.
You'd want to use a soft fill to avoid damaging protective wraps.

    Bookmark   August 14, 2009 at 8:53AM
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