Outdoor pergola

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Forum topic by YS91 posted 05-29-2019 04:01 PM 291 views 0 times favorited 3 replies Add to Favorites Watch
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1 post in 110 days

05-29-2019 04:01 PM

Topic tags/keywords: pergola outdoor deck woodworking gazebo trellis fence privacy fence

Hi all, first time poster here and relatively new to medium / major projects and need some help / advise!

I have a finished outdoor space on top of detached garage (18’2” x 26’ deck with ~12” masonry 3’ wall surrounding it).

I’m looking to build a pergola on this deck with the load-bearing posts attached / bolted to the masonry wall for support.

I’m envisioning a 12’ high pergola with size 18’2” by 12’ with the remaining deck remaining uncovered. Further I’m looking to surround the entire space with a privacy fence (parallel wooden boards with ~1-2 inches between for light).

For reference I’m based in Chicago, IL so outdoor elements will be exposed with snow / rain for 8 to 10 months of the year with temps reaching 90s during summer peaks.

I’m looking for help in the following design & build elements:

1) For the pergola, I’m considering that I’d need 4 6”x6” corner posts, 4 4”x4” posts for the horizontal bars for connecting the corner posts and finally, I’m thinking 1” x 4” boards for covering the top of the pergola (at slight angle allowing for some shade).
For the privacy fence I’m thinking 10’ high 4”x4” posts bolted to the inside of the masonry wall with 1” or 0.5” thick 3” wide boards with ~1” spacer allowing for light / air flow.

2) What wood should I be looking at for this project? Cost is going to be important but I’m also concerned with long term maintenance required on the pergola since it’s outdoors and exposed to the elements.

3) I’d really like to only use 4 6×6 posts for support to have better flow in the usable deck area. Are there any problems with using top horizontal bars (sorry, not sure if it’s called something specific) as two of them are going to be ~17’9” long?

4) I’m not looking at a cantilevered pergola design with the ~18” or so overhang, but rather something modern with clean corners. Given this corner, is there a specific join type I should consider for joining the vertical corner post with the two perpendicular horizontal bars?

5) If any of you have a design plan for this already and are able to share or point me to one, that’d be super helpful too!

6) I’d imagine I’m going to need someone to help out with this project given the sheer size / dimensions / weight of some of these items, but if anyone has had success in working alone with this, I’d love to hear about snappy tricks and learnings along the way!

Thanks in advance everyone, and look forward to hearing some great feedback here.


3 replies so far

View therealSteveN's profile


3591 posts in 1051 days

#1 posted 05-30-2019 04:32 AM

Western Red Cedar (WRC) is going to be your best choice for the $$$$$ Other woods for outdoor use are White Oak, Ipe, California redwood, Teak, bald cypress. There are others from distant lands, past WRC and White Oak, you are looking at a cost factor, that for me anyhow eliminates them quickly. I am in SW Ohio, and that factors in the price. A fella in Louisianan could get Cypress cheaper then me, so maybe for him that would be the deal.

If this is something that will ultimately fall under your home owners insurance my advice is to consult an architect familiar with outdoor design for the how, why stuff. Something goes South, and injuries happen, you may find yourself uninsured otherwise. Local code must be followed, and sound building practices must be followed. Hammered, and screwed together junk isn’t enjoyable to use, and will not increase your homes worth, even if no one gets hurt.

Out in the middle of your yard, hardly any of this applies, except the wood choices. It’s that simple.

-- Think safe, be safe

View tmasondarnell's profile


115 posts in 2266 days

#2 posted 05-31-2019 05:25 PM


You have a lot going on there and not a lot of experience

First off—materials. I will probably be kicked off the site, but for what you are doing, where you are and your budget, you need to use pressure treated lumber.

Second 6×6 are great for your corner posts. 4×4 for your “horizontal bars”(joists) is not going to work. They will not span the 18’ or even the 12’—they will twist and sag. You are going to need a 2×10 or better a 2×12.

Third, 1×4 are great for slats for the roof, but you are going to need to support them every 18”-24” across the span—otherwise they will twist and sag. You will have similar issues with the privacy fence

Fourth, have you considered how you are going to cross brace the corners? Something that size with all of the sail area from the privacy fence is going to want to rack.

Fiftieth, you need to pay close attention on how you anchor it to the roof. Being 10-15’ in the air and having the sides, roof (even as slats), this structure will have significant uplift potential. The first time you have a major storm, you don’t want to see this structure going over the rainbow and into the neighbor’s car.

View bondogaposis's profile


5513 posts in 2828 days

#3 posted 05-31-2019 07:47 PM

My reaction to what you describe is, “gone with the wind”. I think you are going to need the help of an architect or engineer to design something that wont leave on the next storm. How are you planning on getting a permit to build this? I bet they’ll want to see some plans.

-- Bondo Gaposis

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