I would stick with 6×6 posts, The beams are best narrower than the posts and deeper too. Narrower beams can let-in by notching the posts to receive them. This allow for a secure connection between post and beam with less invasive hardware or penetrations in the tops of the beams. Countersinking lags in the tops of beams exposed to the elements invites decay and failure.

Here is a photo of the posts I notched for beam connections a few months and a photo of this odd shaped pergola:

!http://i436.photobucket.com/albums/qq88/knottree/IMG_2018.jpg!

 

btw, 3×8's are available in cedar. beams gain more strength by having depth vs. width.

3×8's may also be $3 a lineal foot cheaper than 6×6, support a similar load, and be lighter weight.

 

The part of the posts that run up flush with the tops of the beams is on the inside of the beams, if that makes sense.

 

Basswood nailed it.

kind of a weird design…. If everyone started swinging at the same time it could get a little bumpy - Ha!

Not crazy about the octagon - awful lot of vertical 6×6s in a small area. not sure…..hmmm. Using 4 6×6s would save you a lot of money too.

besides, if built right there's no need for those massive 2×6 diagonal supports. They're huge and don't add much as far as looks go. 2×4s or 2×6s on edge like the example above might look better and give a little shade.

Are you going with the porch swings? maybe have only two facing each other and one bench could be fixed, at least they won't crash into each other.

What do you plan to put under it? Pavers? blue stone is cool. I couldn't help notice the concrete piled around the posts in the picture. That's going to be a real pain to deal with if he adds a stone surface. You probably saw that too.

BTW - did you thumb thru his other photobucket pictures? He is a hunter who built a similar 6×6 post structure for his pet eagle which he seems to be using as a way to catch rabbits! The wildlife photos of the turkeys are really good too….. Great pictures.

Be sure to follow up with a project post….we'd like to see what you come up with!

 

Thanks for the input! The reason I prefer 4×4s is because 1) They're a lot easier to work with 2) I can get them from Home Depot which is 1/2 mile from my house. 3) I can fit them in my van It IS a weird design, looks pretty awesome, but I figured 4×4s might work because I don't think I want 5 huge porch swings like he did - probably just some of these:

Couldn't 4×4's hold the weight of that?

 

You probably don't want 4×4's from Home Depot. The are almost all "boxed heart" stock, meaning the pith or center of the tree is in the center of the 4×4. This stock usually warps, twists, checks and generally behaves badly.

You want "free of heart" posts. I would not build this with 4×4's either.

 

Wow, first post and I'm already learning! Alright, alright, I'll take your advice and find some 6×6's. Lol. Thanks!!!

 

One of the things we incorporated into our pergola was building up the posts with 2x material rather than solid posts. We did this for a couple of reasons; we didn't want to have the "boxed heart" effect so aptly illustrated by "basswood" above, and we wanted to be able to run electrical inside the post for lights, etc. We used a Kreg Jig for the joints we could get to with it, and then plugs and screws to close it up.

You might also take a gander at Project 50515 by Kiefer, which shows how he built his posts with half dovetails.

 

Nice pergola.

Now don't put the posts in concrete. They will rot.

Fill with gravel and tamp.

If it were be, I would get it built with 2×4 bracing on the up rights, then tamp the posts. If you don't get them perfectly measured and plumb. You will tear your hair out.

What kind of wood ?

 

Was going to use some douglas fir 4×4x8 pressure treated. Thanks for the tip about the concrete. Here's what I'm thinking. I don't need this to be a huge project. Something simple, so I don't want to mess around with hefty 6×6s.

No concrete- something like this:

http://i60.tinypic.com/akihki.jpg[/IMG[/URL]]

Here's a simple sketchup:

http://i59.tinypic.com/2q8rfk0.jpg[/IMG[/URL]]

and

http://i60.tinypic.com/14aiyd5.jpg[/IMG[/URL]]

 

Those ground spikes should help alot.

If you use PT make sure you seal every cut. If not you are just throwing $$$ out.

Just a thought. The end surface of a 4×4 AKA 3.5×3.5 is not that large. The 2×4 s if not pre drilled will split. You may consider some sort of Simpson bracket. Better yet some type of wooden angles elements to add some meat to attach thing to.

Not a lot of Racking resistance in that design.

 

You can also get 4X6s. Cheaper and easier to work with (Lowes should have them). On the beams that hold up the seats just keep the 6 inch side oriented up/down.

 

4×6s….........I may try that. But, then I couldn't use the ground stakes. Any recs on alternatives to that??

 

Where are you located? The last pergola I built I used 6 by 6 eastern red cedar posts. When I built a roof over my deck I had eastern red cedar posts cut that measure 4 1/2 by 4 1/2. These look great and were just the right size. Not too big, not too small. Of course you need a local source. If you have that source, you can get all of your materials of eastern cedar. I paid less than $100 for 6 post 8' long. Just a thought.

 

I don't know what the stakes are - those things that people use for mailboxes? You might be able to bend two opposite sides of those outward, so the 4X6 fits on top of it. Personally I think your posts need to go in the ground if people will 'swing' on this. You're just making extra hinge points that may fail if the post is just nailed to one of those pointy stakes. Look in the galv. plate section of the home center and pick up a booklet from Simpson Strong Ties. They probably have some good ideas. Or browse here:

http://www.strongtie.com/products/connectors/index.asp#

 

Sorry for the late reply. I'm in Phoenix, I know there are some lumber yards near me, just haven't been to one!

Dhazelton - Is there a product in particular that you'd recommend?! Should I look for corner braces, what? It's a bit overwhelming, and I've never tackled a project this big. Mostly, I do furniture and basic home improvements. Nothing this big or "structural". I'm very appreciative of the input as I'm sure you all have much more experience than I do…..

 

You have to have lateral restraint for your stucture. The original picture really could have significant lateral loads with the swings filled up and everyone swinging. I would ask the original designer how far into the ground he placed those posts as this is the only restraint for the posts.

You may want to consider portal frames. In this case, you could set the posts atop a poured foundation

PT wood can be placed in concrete without rotting, you should allow drainage out of the bottom with gravel and slope the top. I also coat the bottom and up a few inches with copper napthanate for added protection.

 

Aside from the structural and joinery concerns, 4×4s wouldn't look right to my eye. They would look spindly.

 

Ditch the stakes, worthless. I would put the hole at least three foot down for strength, keep from racking. Throw a cookie on the bottom and set on top of that, surround with gravel and tamp. And I would stick with the 6×6's .6 pressure treated. Good Luck