On 9/15/2019 3:36 PM, DerbyDad03 wrote:
I'm considering a building a small Pergola, with the 4 posts standing 4' deep
by 6' wide, with 6' x 8' rafters. I'm not sure about the exact dimensions yet,
but that's close. Overall height will be 7-8'.

For various reasons, including location and permits, I don't want to sink the
posts 4' into the ground, use screw in post-anchors, footers, etc. I basically
want the entire structure to be freestanding.

I'm thinking about building a ground level deck, using 2 x 12's as a base frame,
and a multitude of fasteners to attach the posts to the frame. IOW, 11" of post
attached to the frame. I'm willing to add extra structure as required to support
the posts. Any joists not in contact with the posts will probably be 2 x 8's and
the entire deck will be recessed into the ground, leaving about 4" exposed.

Is this thing doomed to failure?


What I did many years ago might be similar.
Approximately 36 years ago I built a 10x12 deck with 2x12 around the
perimeter. Posts sunk approximately 12~18" and surrounded with concrete.

About 4 years later I built a cover over the deck using 10, 4x4 posts on
the perimeter. The posts are anchored to the top of the deck with
Simpson post anchors. Basically a U shaped bracket anchored to the deck
and the post sitting in the U and screwed to the bracket. I added rails
with pilasters between the posts except on the front center entrance and
back center entrance. The top is corrugated galvanized steel panels

During hurricane Ike, I added 3, 1x4 diagonal cross braces to stiffen
the structure. With out the cross braces there was always a little
wiggle in the cover structure. BUT the wiggle was never enough to worry
about until the hurricane, approximately 21 years later. Immediately
after the storm I removed the cross braces.

Today, some 30 years after I added the cover to the deck it still has
just a little bit of wiggle but is as sound as the day I erected it.
Our son has been enjoying the structure for the past 9 years, since he
bought the home from us.

If you are not anchoring to the ground you should be concerned about the
overhead structure possibly catching the wind and lifting the structure.
Granted a pergola is mostly open but you never know.