Free Standing Pergola Advice

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Old 01-21-15, 10:38 PM
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Free Standing Pergola Advice

Hi All,

I need some advice/help with the build of my "modern" simplistic pergola. I have started the project with 4x6 posts (Doug Fir) cut to a height of 9'. Each is placed on a post footing, 12" concrete diameter, 2 feet into the ground with jbolts and simpson strong ties to the 4x6 held in by two carriage bolts. I can say I pretty much understand the MAX spans I'm allowed to use with the wood I, but not as much the total load.

The post are spread about 10' across the x-axis and 13' along the y axis. The 6" side of the 4x6 is running along the y-axis. I would like the pergola itself to spread about 10' along the x-axis and 16' along the Y axis, so there will be a little overhang from the posts, about 1.5' on each side, on the y axis. I would like to run 2x8x16s along outer side of the posts of the y-axis and 2x6x16s, flush bottom with the bottom of the 2x8, along the inner posts, attached by carriage bolts. 2x8x10s will run along the x-axis on both ends, attached by a corner brace on both the 2x8x16s and 2x6x16s. 2x4x10s will then be placed parallel to the x-axis at 1' intervals ontop of the 2x6s to provide shade.

I was wondering if anyone could point out any flaws with this design. Will i need to place another 2x6 in the center parallel to the y axis, attaching them to the 2x8s along the x-axis? Will that cause sag?
 
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Old 01-21-15, 11:05 PM
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Welcome to the forums.

I'm not a builder just a question.... did you have to get approval or get a permit for your pergola ?

A friend of mine just had one done. He had to have the plans approved, the footings inspected and a final inspection done.
 
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Old 01-22-15, 01:24 AM
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Being in earthquake country, for sure your local AHJ will require a California licensed engineer to design the structure to minimize damage and maximize stability in the event of an earthquake, even a minor one. Us amateurs on this forum don't quite meet the criteria.
 
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Old 01-22-15, 03:49 AM
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I agree with having drawing made and approved for your area. I question Douglas fir being used in a wet environment. I also question 13' span for 2x8 lumber. Construction of your pergola will be similar to building a deck, so some of the methodology will be the same. While you are waiting on your engineer, you may want to brief yourself using the current standards of deck building, which show what can and cannot be done. http://www.awc.org/Publications/DCA/DCA6/DCA6-09.pdf
 
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Old 01-22-15, 05:36 AM
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We can help you when it comes time to build, but planning is difficult via a forum.

I recommend a visit to your local building department. The building department does not have plans that you will use to build your pergola. However, they have "typical" plans. These plans show minimum requirements, all connection details, footings, any rafter tie details, you name it.
Following their guidelines will go a long way to getting your plans approved.
Be sure to also pick up a info sheet on setback requirements. This sheet will detail distance from property lines and house structure, pools. Hopefully that won't apply.
You can ask them about engineering, I don't think it's required when following the details they list.
 
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Old 01-22-15, 09:45 AM
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To address a few questions:

Im covering the douglas fir with a oil based primer, and then with a solid stain. I was told that would protect the wood from the elements, which are not too harsh in CA.

Looking over the span calculator, on a ceiling joist, a 2x8 can span across 18' and a 2x6 can span across 15' on a 10PSI Live/Dead load. That should cover my pergola?

As far as permits go, a detached structure, covering ground area of 120sqft does not require a permit in my county. I know my structure will be 160sqft, but I was hoping to avoid dealing with the entirety of that issue. I can knock it down to a 10x13 (at that point whose counting) if I have to go with no overhang, but avoiding the whole permit issue was my goal.

Thanks for the comments though, I thought it would be pretty difficult to address my issue with just text and no 'sketches' or rough drawings but just gave it a shot anyway.
 
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Old 01-22-15, 10:01 AM
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We can still help. Like I said, the city probably wouldn't require engineering anyway.
So all you have to do is follow a typical design. Sounds like your footings are great.

I'll study your first post some more, it's just hard to get my bearings straight.

One thing you probably already know:
The Load carrying beams will sit on top of posts, not be attached with through bolts.
 
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Old 01-22-15, 10:12 AM
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Thanks Handyone!!

What would be the issue with a side mount with bolts, instead of top mount. My design calls for something that looks similar to the following Picture

Again, mine will only have 4 posts. but would have 2x8s as well as 2x6s running along the y-axis.

Ill try to get a sketch done so that it is better illustrated.
 
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Old 01-22-15, 10:29 AM
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Yeah, that picture is fine. You don't need to worry too much about loads. The boards will only be carrying their own weight.
What I was getting at was a beam across the tops of the posts. Then much larger (4 x 6) members are laid perpendicular across the beams, stretching the depth of the pergola. Additional members are then laid on that.

One thing you can do is go looking for what you want. These pergolas are everywhere in CA. Condo complexes, parks, you name it.

So you can use through bolts. This is a "lightweight" structure.
 
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Old 01-22-15, 10:45 AM
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I said above that through bolts will be OK. Here's a picture of ideal post to beam connections:

Name:  posttobeam.jpg
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Since you're building a lightweight structure, you will probably be OK. As much as possible though, try to duplicate the connections shown in picture.

You can see why it's much stronger.
 
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Old 01-22-15, 11:36 AM
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I see what you mean.

I provided a "very rough" sketch of what I was talking about. Sorry for the 1st grader project quality.Name:  Quick Sketch.jpg
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My two main concerns:

First is with the bracing at the overhang in the corners. How can I connect the purple 10' 2x8 to the 16' 2x8 and 16' 2x6?

Also would I need another 2x6 between the two red 2x6's in order to stabilize the structure and hold the 2x4's without sag. Or will that extra 2x6 in the center itself sag if connected to the 2x8x10's perpendicular to it?
 
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Old 01-22-15, 01:19 PM
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Since you're in California, redwood would probably be a better choice for the posts. It's easy to get around here and will hold up better over time. Doug fir should be fine for the upper members.

The one thing with your drawing is that it looks like the 2x6 is being used to support much of the 2x6, also the connection holding the tops of the posts together on the short axis at the top is pretty indirect and will rely on the corner joints between the 2x8 perimeter members. I'm not saying it's too weak for what it'll be doing since there's so little load on an open-member pergola, but it could be built much more solidly with a minor modification (which will alter the look a bit).

Personally, I'd through-bolt the 2x6 across the short sides a little (4-6 in) below the post tops (I'd use stainless hardware if you're doing a stain/oil finish rather than paint, but galvanized is probably sufficient). Then set the long-edge 2x8 members on top of the protruding ends of the 2x6 and through bolt those to the posts as well (inside the posts or else you'll need to have the 2x6 protruding past the posts by at least 2"), then put the top pieces across over the 2x8s. If you want the ends of the top pieces covered, use a 1x4 or 1x6 fascia board screwed into the 2x4s with a couple 2" deckers at each end.
This will look a little different with the lower cross-braces, but will be more solid and should withstand any earthquake not strong enough to level your house (at which point you've got bigger problems than the pergola).
 
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Old 01-22-15, 02:14 PM
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I was going to do redwood, but i realized it doesn't have the same span ratings as Douglas fir and it wouldn't work with my situation. I believe ive properly prepared the doug fir for the elments, but only time will tell! I will be using redwood however for the 2x4s going across the top.

Hmm...I see what your saying, maybe i could sandwich the posts between 2 2x4s that run on the top. Using either lag screws or carriage bolts. That should hold the posts together along the short axis, and maybe make less of a design change?

Can anyone suggest and link me to interior corner braces that could be used for the 2x8s?

Also, any ideas on the addition of another 2x6 along the longer axis in the center between the two existing 2x6s? Will it add to or subtract from the stability?
 
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Old 01-22-15, 02:21 PM
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Name:  Quickpergola.jpg
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The black lines (2 x 6) will also be through bolted and sandwiched to the posts.

The long side 2 x 8's will rest on these and be bolted through posts.

The inside 2 x 6's are still in debate, I would like bmgreene's opinion.
 
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Old 01-22-15, 02:32 PM
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Are the new 2x6's being use primarily to hold the posts together along the shorter axis. Or to hold up the 2x8 and 2x6 along the longer axis?

In my latest post I asked if sandwiching the posts between 2 2x4s on top would suffice...thoughts?
 
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Old 01-22-15, 03:03 PM
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The 2 x 4's are just decorative or to provide shade.
The sandwiched 2 x 6's on each post will serve to hold posts together and support the long side axis, 2 x 8's.
I think you should redesign your pergola based on that.
You'll save in lumber and it will be more sturdy.
 
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Old 01-22-15, 03:05 PM
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A general rule of statics is: The amount of sagging of any long-span member is inversely proportional to the depth of the member, meaning deeper members will sag less than their shallower cousins. That's why it always makes sense to use deeper members for longer span structural supports, and shallower members for shorter, less critical elements. Not the other way around.

Also, I'd be careful when drilling the column tops for through bolts--making them look like Swiss cheese will weaken their ability to perform when the wind picks up and wants to move the entire roof system to your neighbor's yard.
 
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Old 01-22-15, 03:32 PM
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Well,
I started out by saying beams should rest on top of posts. After all the thought and input above, we need to start over. It's true that through bolts are not ideal.
 
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Old 01-22-15, 03:38 PM
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Ok looks like I'll go with the 2x6's to Sandwich the posts. At the same time, if I was to still use a 2x8 on the shorter axis, would the corner braces be enough to hold it or would heavy sag be involved? The reason why I ask is I rather have a consistent look of thickness rather than do a 1x8 fascia board on the short axis screwed into the 2x4s.

As far as bolts go, each post should received just 4 holes (should'nt be to swiss cheesy), two for the 2x8s and 2 for the 2x6.

Any recommendations on bolt size? Also, should the bolts be staggered or stacked on top of another.

On a side note, had a question regarding patio hanging heaters. If I was to attach a hanging gas heaters, would the 2x4s running across hold the heater? Or what are recommendations on that.
 
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Old 01-22-15, 03:42 PM
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So I should be considering lag bolts instead?
 
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Old 01-22-15, 05:03 PM
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The short side 2 x 8 should be able to span without sag.
We are losing focus here (maybe just me) and need to concentrate on post to beam connections. That's all that matters at this point. Once you have a secure base you can add to it.
Hopefully some others will have some input. I'll try to make a drawing in the next 24 hours or so detailing a few options.
 
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Old 01-22-15, 05:22 PM
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carriage bolts with washers/nuts would be better than lag bolts for the major connections, through bolts won't degrade in strength if the wood rots or gets infested the way that lag bolts could (very unlikely, but why not eliminate the possibility). Worst case on through bolts would be that the threads rust together and they get hard to remove, this doesn't really compromise shear strength. Since the span limitations are based on assumed levels of supported load which won't develop on a pergola, I wouldn't worry about that in lumber selection, and the resistance to rotting of redwood should be more important for the columns than the rated strength (4x6 posts on a pergola might almost be sufficient if you were using balsa wood, 4x4 redwood would really be enough), and keep in mind that PT wood is now illegal in CA (if nationally).

part of the benefit of stacking the long axis and short axis beams vertically is that both can be cross-bolted in two places each while allowing the holes to be spaced 2.5-3.5 inches from each other to keep the columns from being over-drilled.

using the upper 2x4s to tie the tops of the columns together across the short axis would be better than nothing, keep in mind that sandwiching the post with these boards will drive the spacing for the rest of the upper members and may leave you with a lot more cover density than you intended.

Handyone's drawing looked like it's pretty close to what I had in mind; sandwiching the posts with 2x6 on the short edges is probably more strength than you'd need, but could give a better look due to the symmetry of it. Having both the inner 2x6 and outer 2x8 on the long axis is probably more than what's needed, just the 2x8 would probably be sufficient, depending on the density of top members you're planning on using, 2x4s will be pretty heavy up there and you might want a third member along the centerline (another reason to have the short axis cross members under the long axis beams); any inside supports would need to be the same dimension vertically as the outer, though or it won't set high enough to support the cover boards.

A lot of the structural needs will be determined by the cover density. If you're spacing the 2x4s with 1.5-3.5 inch between the faces, that's a very different setup than if you're looking at spacing them 7-9 inches apart since the weight on the beams will be very different, especially as the finish on top starts to wear and the wood might absorb rain water (also it could make a difference whether you're in SoCal or NorCal with the difference in climates).
 
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Old 01-22-15, 05:29 PM
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I hope we are not, I am still actively trying to figure out what type of hardware/method should be used for the post to beam connections.

The positive about the 2x6 onto the inner post is that it will allow me to rest the 2x4s right ontop. From what I am collecting. The negative of using the 2x6 would call for using carriage bolts I'm assuming due to the pass through from 2x8 to post to 2x6.

Without the 2x6 inner post, I can use lag bolts to attach the 2x8 to the post. Then in order to avoid overlapping bare ends, due to design choice, I would need to use hangers on each 2x4 attached to the 2x8 beam.

With regard to the 2x6 along the short axis, I could also place that flush with the bottom of the 2x8, not resting the 2x8 on top. Could then use corner brace between the 2x6 and 2x8 if additional support is necessary for the 2x8.

Anyways, those are my current thoughts, would love to hear what you guys are thinking!
 
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Old 01-22-15, 05:42 PM
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Im in SoCal so rain is almost a non-issue haha...we are in a drought and things may not change. As far as 2x4 spacing. I'm looking at nothing less than 6"s, and even that is considering that I could use the 2x4s to sandwich the short axis post to post. Otherwise an 8" span seems fine.
 
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Old 01-22-15, 06:41 PM
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things to consider:

having 8 inch spacing of the 2x4s over along the 16' long axis means 24 2x4s total, so don't worry too much about weight - one 2x8 along each side over the long axis should be ample, these should be set with their upper faces even with or just a little above the post tops if you plan to close over the ends of the 2x4s with a fascia. Crossing the short axis with rails under the 2x8s will provide good stability and make it much easier to put up the long beams since they'll be set in place before bolting to the posts; a single 2x6 on each end would be sufficient, or you could sandwich the beams with a pair of 2x4s on each "end" for a more symmetric look - even 2x3s would probably be enough for this since they'd really only be supporting their own weight with no center beam, and they're really there to keep the posts parallel, 2x6 would give the most area for spacing out two bolts which will help reduce (but won't totally prevent) racking of the whole framework.

Are your post footings already in place, or is there some room for adjustment on the placement? If the posts will definitely be 10' apart on the short axis (I'm assuming this is 10' on center?), then setting the 2x8s inside of the posts will allow you to just lay in 10' long 2x4s with minimal trimming, putting the beams outside of the posts will mean using 12' studs and cutting them down to just a bit over 10' (which will add some extra cost and leave you with a bunch of scrap wood that's mainly only good for making fireblocks next time you frame in a wall). Covering the ends of the 2x4s with a 1x4 fascia board would give you a very similar look to what I think you're going for with this,

most metal hardware like simpson ties and joist hangers will be hard to find in anything but a galvanized finish, which will likely be unsightly with a more natural looking (oil/stain) finish, if you're going to have a bunch of metal straps, think paint rather than stain or else be ready to mail-order a lot of hardware at a premium price, most likely. For bolting parts together, I'd recommend carriage bolts over lag bolts no matter how you plan on arranging the assembly since even if they're close together you'll degrade the columns less with drilled holes than with a bunch of large screws driven in (and have less risk of splitting the wood apart). If you want to get really fancy, this could all be built up "amish"/woodworking style with dados and mortise/tenon joinery along with maybe some dowel pegs and wedges using no metal at all except for the hardware connecting the posts to the concrete piers, but that's a ton more work, requires some extra tools and not knowing your skill set or amount of time you'd like to invest in this, we'll stop at acknowledging that it's possible.
 
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Old 01-22-15, 07:15 PM
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Hey bmgreene,
Can you follow up on this thread and hang in? I like your thinking.
Tomorrow I want to post a front elevation, see what tekgarage and you think.
 
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Old 01-22-15, 08:31 PM
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Wanted to give you guys actually Dimensions before diving further...sorry wasn't home when I initially posted this but remembered rough figures, again sorry for any confusion. My anchor bolts are spaced at 11'6" and 13'2" on center exact. They are quite odd lengths but at the end of the day that's what I'm working with.
That should provide for very minimal cutting of 12' members that I can just toss after the cut.

I'll be working on some extra plans/options myself and will share as soon as I get them up.
 
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Old 01-22-15, 08:41 PM
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As far as hardware goes, and there unsightliness....this is exactly why I wanted to attach the 2x6 along the inner post of the pergola. It would allow me to cut out notches on the 2x4 to place directly over the 2x6, without using 48 joist hangers.

My end goal for this project is to make any metal hardware almost invisible. I plan on surrounding the base of the columns with stone column about 2-3' high to cover the Simpson ties on the bottom. The solid stain I'm using should cover any visible hardware, or so im told.

Cant say that I want to go Amish with it, as I simply don't have the time for such a project.

the 48 joist hanger option really urks me, and would like to avoid the 2x6 under the 2x8s if possible. Im even willing to do a 2x6 on the short axis even with the 2x8. I just don't want the height of the pergola dropping another 6" if at all avoidable.
 
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Old 01-22-15, 08:51 PM
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Oh and the color schema is a dark brown almost black solid stain, applied to everything but the 2x4s. The 2x4s will be getting a transparent stain with a 3:1 ratio mix of natural sequoia to golden honey respectively.

So covering the joist hangers with paint against the transparent 2x4s will look nothing less than an eyesore in my opinion.

BTW you guys rock, thanks again!
 
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Old 01-23-15, 12:39 AM
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Here's one idea for the joinery at the tops of the posts.Name:  IMG_20150122_233615.jpg
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The "dado" cut (1.5x5.75) in the center of the long side of the 4x6 would allow a 2x6 to be set inside and sit a bit below flush with the top end of the post. the "rabbet" (1.5x3.5) would be on the outside faces of the posts and would need to have matching cutouts in the 2x6 rails, the 2x8 beams would set in these cuts leaving enough room for the 2x4 cover boards to be set into dado joints in the beams (1.5x1.5 inch notches should work with the 2x4 ends cut accordingly) sitting flush on top. The cover boards can be attached to the beams with 3 inch deckers, and the marked locations in the post top joinery would be drilled through for 5/16th or 3/8th diameter carriage bolts.

These cuts could be done with a hand saw, jigsaw or sawzall only, and a drill guide would be useful forkeeping some of the through holes aligned but isn't absolutely necessary. Some of the cuts would be easier to make with a router or oscilating tool though.
 
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Old 01-23-15, 10:34 AM
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I like the idea of doing these cuts, the only issue is, I'm cutting into the 2x8 to lay in the 2x4s. Design wise, this wont work for me...unless I attach a 1x8 fascia board directly to the 2x8 to cover the ends of the 2x4. But at that point is it not too bulky in that area?

Anyway I think of it, the additional 2x6 has to be placed along the long axis, allowing the 2x4s to rest ontop . Eliminating both the need of a fascia and hangers. I think I could apply your rabbet method to the posts for accommodating both beams.

Once that is set, I completely agree with the fact that I need the cross member along the short axis.

What are thoughts on the following:
Name:  Post Cuts.jpg
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^or instead of lag bolts, attach the bracket by putting through bolts through bracket as well as the run through the 2x8 to post to 2x6 and tightening?
 
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Old 01-23-15, 10:37 AM
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Or....is that stupid because there is only 1/2" of post left between the 2x6 and 2x8
 
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Old 01-23-15, 12:09 PM
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I just noticed one thing in my drawing is that it would leave two carriage bolts trying to pass through each other. The upper bolt through the short axis cross piece (the upper of the holes that's located in the view on the right hand side of the drawing) should be located 2 inches farther down.

I think I finally now understand how you were looking at the long members, and the problem with that is that you're using the inner 2x6 as the load-bearing member and the outer 2x8 as basically a very heavy fascia to cover the ends of the cover boards.

If you want to have something that's set up like that for the upper construction then I'd recommend the following for the joints at the top of the post:

eliminate the "dado" cut into the post, but keep the 1.5x3.5 inch "rabbet" cut and rotate the post to have the notch facing the inside. Then sandwich two 1x6 rails connecting the posts across the short axis, set with their tops even with the notch (3.5 inch down from the post top) and through-bolt these to the posts at two points per end with 5/16 carriage bolts. Next, set 2x8x16' beams into the notches and through-bolt those to the posts at two points per joint (also 5/16 carriage bolts). Then lay the 2x4 cover over the beams, cut to end 3/4" in from the outside face of the posts on each side, notching each board 1/4-1/2 inch deep at each crossing before setting up the rails/cover will make the final layup simpler without compromising strength meaningfully. Finally cap the ends of the 2x4s with a 1x8 fascia board which should sit on top of the posts and be flush with the outer faces of the rails (if you care about the fascia and covers being flush on top, you'll need to reduce the post notch depth by the total depth of the notches in the beams/cover boards).

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If you're handy with a router, the notches in the 2x8s can be cut together (this will also ensure the cover boards stay aligned), and the notches in the 2x4s can be cut in batches of 4-5 boards at a time which will speed up a lot of the cutting. All you'd need is a jig for cutting 1.5 inch wide dados and set the depth however you prefer.
Also with shallow locating notches like this, it'd be easy to use a pocket hole jig to set pocket holes in the 2x8s which would run up into the 2x4s, facing them upward will prevent them from filling with water in rain, and putting them on the outer faces of the rails will leave them nearly invisible once the fascias are put on.
 
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Old 01-23-15, 02:27 PM
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Ah I see, so i should be using the 2x8 as the load bearing beam instead and cover with a fascia...that makes more sense bmgreene.

One thing that I'm trying to avoid are these windows between boards... So with a little modification to yours I came up with this.

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Here you can see I removed that elevated window of space between the 2x8 and 2x8. I can notch the 2x8 2.5" and the 2x4 1" (or 2" and 1.5"). Thoughts on the stability of this design???Considering 24 2x4s?

I would like to alter the 1x6 as well due to the same issue, the window between the 1x6's and the bottom of the 2x4? Anyway I can place the top of the 1x6 flush with the bottom of the 2x4s. Maybe a joist hanger in between the 2 posts and a 2x6 instead?
 
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Old 01-23-15, 03:24 PM
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that would work, although if the 2x4s are notched 1.5 inches, you'd only need to notch the 2x8 to a depth of 1 inch rather than 2.5 (notching both will make the lay-up much easier as long as the notches align. It'd probably be worthwhile to cut the notches in the 2x4s to a width of 1.3/4 inch and the ones in the 2x8s maybe 1 5/8 inch unless you don't mind having to pound some things together with a mallet.

Also make sure you use a stainless or coated decking screw if you're going to screw down from the top since the pocket which will form around the head would then be a place for water to pool, and make sure you treat the 1-by boards with something like linseed oil before staining to reduce the potential for cupping over time.

the aesthetics are your choice ultimately, but don't worry too much about the "window" since those would only exist if a cover board happens to be right over a post, and even then it'll be 9 feet off the ground and rarely in anyone's eyeline unless they're looking for it.
 
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