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Olafhenny · 05-05-2012, 11:42 PM

Sorry, Dean, I am a bit late, but it looks, like you need a bit of engineering advise. As your structure
stands now, I disagree with Scuba Dave that it will blow over at 40 to 50 mph winds. If you put
anything on it, which will catch the wind, such as vines, it will blow over at less than 20 mph. Your
joints at the corners will act like hinges and make the structure fold like a card house, digging the
posts deep will help a little, but not enough.

The very least you will need is diagonal cross strapping. No need to do it across the whole span of
the beams. 3 feet x 3feet from the cross beams to each post will give it plenty of stability.

But if you want that structure to stand up for 10 years or longer, I am afraid you will have to start from
scratch: Dig the post holes about 1 foot deep and at a diameter of about 8 to ten inches. Important
is, that the walls of the holes are undisturbed soil (no lose dirt). Fill the holes with ready mix
concrete. You will need a bag for each 2 to 3 holes. Into that concrete you plant a post bracket
for each post as you see in the top left corner of this site:

post base brackets - Google Search

Make sure these brackets are lined up, sighting from post to post. Having them all the same
elevation will help too. You can ensure that, by using a carpenter’s level and the straightest one
of your 2x4s for the top frame to get them all to the same height.

The idea of the brackets is, that you do not want to have direct contact between concrete and
wood, no matter how well the wood is treated, incised or otherwise. Concrete will make and
wood rot prematurely.

Another bit of advise: Don’t torture yourself by using nails. Beg, steal, borrow or rent a
cordless drill and use 3” special screws for treated lumber. The job will go twice as fast and will
require a lot less foul language to get it done.

Good luck,
Olaf

PS: I am adding a couple of pictures from my own gazebo construction eight years ago.

You can see, I kept the diagonal strapping a bit shy, but I could afford that, because of the diagonal grid of all the
minor straps.

This is an attempt to blow up part of the previous picture to show the post sitting in the bracket,
which in turn sits in the concrete. It is important, that the concrete is right against the base of the
bracket, for stability, but does not touch the wood.

05-05-2012, 11:42 PM	#18 (permalink)
Olafhenny Olafhenny's Photo Gallery Location: Penticton, BC, Okanagan Valley, Canada Find me on the map! Zone: Hardiness Zone 6 Name: Olaf Join Date: Apr 2010 Posts: 1,705 BananaBucks : 297,528 Feedback: 0 / 0% Said "Thanks" 2,050 Times Was Thanked 2,012 Times in 876 Posts Said "Welcome to Bananas" 77 Times	Re: Arbor/ Trellis design questions Sorry, Dean, I am a bit late, but it looks, like you need a bit of engineering advise. As your structure stands now, I disagree with Scuba Dave that it will blow over at 40 to 50 mph winds. If you put anything on it, which will catch the wind, such as vines, it will blow over at less than 20 mph. Your joints at the corners will act like hinges and make the structure fold like a card house, digging the posts deep will help a little, but not enough. The very least you will need is diagonal cross strapping. No need to do it across the whole span of the beams. 3 feet x 3feet from the cross beams to each post will give it plenty of stability. But if you want that structure to stand up for 10 years or longer, I am afraid you will have to start from scratch: Dig the post holes about 1 foot deep and at a diameter of about 8 to ten inches. Important is, that the walls of the holes are undisturbed soil (no lose dirt). Fill the holes with ready mix concrete. You will need a bag for each 2 to 3 holes. Into that concrete you plant a post bracket for each post as you see in the top left corner of this site: post base brackets - Google Search Make sure these brackets are lined up, sighting from post to post. Having them all the same elevation will help too. You can ensure that, by using a carpenter’s level and the straightest one of your 2x4s for the top frame to get them all to the same height. The idea of the brackets is, that you do not want to have direct contact between concrete and wood, no matter how well the wood is treated, incised or otherwise. Concrete will make and wood rot prematurely. Another bit of advise: Don’t torture yourself by using nails. Beg, steal, borrow or rent a cordless drill and use 3” special screws for treated lumber. The job will go twice as fast and will require a lot less foul language to get it done. Good luck, Olaf PS: I am adding a couple of pictures from my own gazebo construction eight years ago. You can see, I kept the diagonal strapping a bit shy, but I could afford that, because of the diagonal grid of all the minor straps. This is an attempt to blow up part of the previous picture to show the post sitting in the bracket, which in turn sits in the concrete. It is important, that the concrete is right against the base of the bracket, for stability, but does not touch the wood. __________________ The reason I joined this forum was to share experiences, my own and those of others and to learn from them.