Elevated Post & Pier Foundation

[Tom(Guest)]

I am planning on building a small ranch ~24 x 56 in a flood area.  The house wil have to  be elevated so the bottom floor is 8 1/2 feet above grade.  My plan is to place the posts (8x8) on 3 feet deep footings with Simpson anchor braces.  Of course there will be cross bracing and I will have an engineer review the plan.  My question is whether the Simpson braces will do the trick or do I need the posts to be buried?  It will be easirer for me to build if they don't need to be buried.  

[glenn kangiser]

I think diagonal bracing can be sufficient for a tall foundation by itself but the engineer will have to say what it will take in your situation.  If the water is not static then it can easily take out well braced structures.  Condition of the soil and footing will also have to be considered.  Does it get soft when submerged?  Will you sink into it?  Lots of questions the engineer will have to consider to keep your investment from going down the drain.

[glenn kangiser]

Every time we get into a discussion about post and pier foundation heights I think of this cabin.  I finally remembered to take a few pix of it this time.

[John Raabe]

Thanks Glenn:

That is dramatic! Is this in your earthquake area? If so, I'm sure it was engineered? (or maybe not?  :-?).

Notice how most of the posts are triangulated back into the frame. However, I think I would do more of that - there are some pretty tall and slender posts. And some of them are unsupported.

[glenn kangiser]

This is Zone 3 -- interesting -- this is a commercial building - Hostel/Motel - but the cafe building (another building) has open trusses - 20 foot or more span built out of bolted up rough lumber.  No stamps I'm sure and no signs of weakness.  I guess it could be fairly old - maybe grandfathered in.

This one has always been interesting to me.

[Tom(Guest)]

Thanks for these pictures.  It looks as if the footers on the corners of the building (not the deck) are larger than the rest.  Does it look like the posts (are they 4x4s?) are embedded into them?  Hard to tell from the picture.  I also must say that I would have thought more cross bracing would be required. 8-)

[glenn kangiser]

Zooming in on the picture it looks like each post has an embedded galvanized anchor bracket.

As far as the bracing goes-- it looks like a good earthquake could take it all out.

I live quite near here and the soil cover is only a few feet avg. so I assume all footings go to bedrock.