Help with rough design for pergola

Reply

  #1  
Old 06-17-14, 02:12 PM
T
Member
Thread Starter
Join Date: Aug 2013
Location: USA
Posts: 13
Received 0 Votes on 0 Posts
Help with rough design for pergola

All-

We've got a corner section of yard that I'd like to build a pergola over. I've built a simple 4-post 10x10 in the past, and, lesson learned, I wanted to have a plan in place for this one before starting.

The darker border along the top and right is fence. The section labeled "dirt" is what I'd like to cover, as well as some of the decking to the lower left of the dirt (it used to be shrubs and I ripped them out; I'll eventually put some sort of stone/rock/wood flooring down after the pergola is in place). All measured dimensions here are within an inch and the pic is pretty much to scale. The 56" line is just the boundary at which I stopped ripping out shrubs.

My initial thought, which I'd love feedback on, is this (and for reference, this is in Dallas, TX, and looking at cedar here). Four 4x4 pressure-treated posts, with 1x cedar sheathing, at points A, C, D, F. Buried with concrete footings. Certainly not a perfect rectangle but pushed to the edges. Then two 2x10 cedar support beams from A-F and C-D (A-F distance is 139"). The C-D beam necessarily terminates at the fence but the A-F beam will extend. Before going any further, the first problem here is how to get rafter coverage over to points B and E.

Option 1- I could run support beams A-C and F-D, but then I'm looking at a massive amount of cedar tall enough to run those long spans.

Option 2- putting additional posts at B and E, though that complicates the design (and how those rafters would still cover those areas might be a little funny).

So, yes, very unusual shape. Any ideas out there on how to attack this? Would love any and all feedback.

Thank you for reading!
 
Attached Images  
Sponsored Links
  #2  
Old 06-17-14, 03:51 PM
P
Temporarily Suspended
Join Date: Jul 2008
Location: NY
Posts: 10,986
Received 0 Votes on 0 Posts
How did you plan to cover the entire area marked dirt without posts at B & E? What's the distance between A & F? I think that you will need a post between A & F as well.

Basic idea: http://images.landscapingnetwork.com...p-llc_3074.jpg
 
  #3  
Old 06-17-14, 06:34 PM
T
Member
Thread Starter
Join Date: Aug 2013
Location: USA
Posts: 13
Received 0 Votes on 0 Posts
Thanks! I'm not exactly sure how I was going to cover to B and E Extending the slats way out past the rafters might be a way. Distance from A to F is 139" (so under 12').

I like that curved design- I would think on a straight span under 12' the A-F beam could work without a center post- but on a curved beam it's probably a different story. I'm thinking I could do a hybrid with a curved rear beam with 3 posts and a straight front beam with 2.
 
  #4  
Old 06-18-14, 03:26 AM
M
Forum Topic Moderator
Join Date: Mar 2005
Location: USA - N.E.Tn
Posts: 47,554
Received 301 Votes on 267 Posts
Four 4x4 pressure-treated posts, ........ Buried with concrete footings.
It's better to pour a footer with a 4x4 metal bracket to secure the posts. Most of us frown on embedding posts in concrete as they will have a shorter life.
Curved beams aren't really an option. Normally a series of short beams [or end joist], each at a slight angle from the last are used and then just the decking is cut to match the radius.
 
  #5  
Old 06-18-14, 12:21 PM
T
Member
Thread Starter
Join Date: Aug 2013
Location: USA
Posts: 13
Received 0 Votes on 0 Posts
Appreciate the tip.

How much of a concrete footer would you recommend? This is Dallas, 5" frost line, soil is primarily clay, in a yard area with poor drainage (and mild shifting). Maybe 24" deep and 8-12" diameter?
 
  #6  
Old 06-18-14, 04:39 PM
P
Temporarily Suspended
Join Date: Jul 2008
Location: NY
Posts: 10,986
Received 0 Votes on 0 Posts
24" deep should be fine with a 5" frost line.
 
  #7  
Old 06-18-14, 09:26 PM
BridgeMan45's Avatar
Member
Join Date: Oct 2011
Location: USA
Posts: 3,196
Received 1 Vote on 1 Post
You never mentioned how tall the structure will be. But if it was mine, the columns would be 6 x 6 material instead of 4 x 4, and probably not cedar. With white cedar having an allowable bending stress of less than 1000 PSI for No. 2 grade, it's just too flexible for withstanding repeated bending stresses from wind loading--unless watching your pergola dance in the wind is one of your design goals. Since you'll be using PPT material, you could go with one of the stronger species available down there that would be a better structural performer, while not weathering as well as cedar. Realistically speaking, I'd also plan on using somewhat more than just 4 columns, locating them inside the fence line to form as close to a true rectangle as possible for the main structure (for ease of framing), with single columns at the exterior triangular apexes.
 
  #8  
Old 06-19-14, 10:46 AM
T
Member
Thread Starter
Join Date: Aug 2013
Location: USA
Posts: 13
Received 0 Votes on 0 Posts
Bridge- thanks. Think it's going to be roughly the height of the fence, which I'm guessing is in the 9' - 10' range. Structurally, then, is there any reason not to go with stronger wood posts with cedar sheathing, and stick with cedar for the rafters and slats? Also, as opposed to the 6-post method you laid out, I might go with posts at A, B, F, E, and a post roughly halfway between C and D (but making everything symmetric). That way, I can lay out my rafters in a fan not unlike the rafters in the link Pulpo posted.
And I'd necessarily have to notch in the beams to the posts to make the angles I'm going to need to make- or is there an alternative to mounting beams to posts that aren't flush on the post face angles? I could mount on top, but I don't know if I'd like the look and don't know if I'm a lot less structurally sound that way.
 
  #9  
Old 06-19-14, 01:05 PM
BridgeMan45's Avatar
Member
Join Date: Oct 2011
Location: USA
Posts: 3,196
Received 1 Vote on 1 Post
I would never clad PPT columns with cedar, as in my opinion it's too expensive for any visual benefits gained, and the interface between the columns and cladding will always be exposed to rain, never fully drying out. They'd make great future homes for unwanted, tiny critter colonies.

For column-to-beam connections, I'd fabricate custom steel welded brackets, top-mounted on the columns. Using scrap or salvage steel bits and pieces, the cost would be reasonable, and when primed and top-coated black, they'd look good with whatever stain goes on the wood members.
 
  #10  
Old 06-19-14, 07:14 PM
T
Member
Thread Starter
Join Date: Aug 2013
Location: USA
Posts: 13
Received 0 Votes on 0 Posts
Bridge- great information, thank you. Just measure the fence, and it's only 8'. Aesthetically, would it look bad to make the pergola 9' or 10', or should it really be kept fence-high (or possibly a few inches taller)?
 
  #11  
Old 06-19-14, 10:16 PM
BridgeMan45's Avatar
Member
Join Date: Oct 2011
Location: USA
Posts: 3,196
Received 1 Vote on 1 Post
I can't comment on what aesthetics would work for you--that has to be your decision.

But if you go ahead with cladding the columns, just remember to propose a toast during the social gatherings you have under the pergola--"Here's to all of the insects and critters we invited to our picnics, so they'll remember us when they take over the world."

It was always good for a few laughs when I used it in the past.
 
  #12  
Old 06-20-14, 01:48 PM
T
Member
Thread Starter
Join Date: Aug 2013
Location: USA
Posts: 13
Received 0 Votes on 0 Posts
It's a done deal- no cladded posts I think I'll be going for 6 posts (A-F, and B, E, and two more equally-spaced between B and E but back against the fence as much as possible). It will either be 8-ft. posts with beams on top or 9-ft. posts with beams on the sides bolted through. I'll also have corner bracing all the way around. Given this, would 4x4 posts provide for a rigid enough structure?
 
  #13  
Old 06-20-14, 05:14 PM
BridgeMan45's Avatar
Member
Join Date: Oct 2011
Location: USA
Posts: 3,196
Received 1 Vote on 1 Post
It depends on the grade of steel and wall thickness. Too soft or thin, and it will wobble.
 
Reply
Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description: