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Decks/Deck w/ Pergola - Girder beam


I am building a deck that is about 3' off the ground. It is an 'L' shape type of a deck. The short leg of this deck will contain a 12 X 12 (appox) Pergola. I planned on using (4) 6X6 posts (12' high)for the Pergola and the rest of the post will be 4X4 post to support 2X8 girder beams for the deck. My question is this: I have one long girder beam section. I need to use the Pergola post to support the girder. All deck posts are sitting on 12" footings/ 4' deep. How do I attach the girder beam to a 6X6 pergola post and not disrupt the stability of that post? Do I notch out a 3" area to set the 3X8 (using 2 2x8) girder in or do I use a through bolt and sandwhich two 2X8's between the 6X6 post? The Deck floor will sit shy of 3' from the ground level and the Pegola will stand about 9' from deck floor. Lastly, (if i can use the pergola post) can the girder beam be spliced at that Pergola post (butting the joints) or should I overlap and go to the next avaiable post for a splice?
I haven't seen anything on this and I figured it be best I ask an expert. Other Pergola's design I have seen are mounted straight to the deck floor, which seems unstable to me, given the wieght of these pergola's.
I really appreciate your time!
Thanks for any feedback.

Hi Shane,

  Well, without seeing it, or knowing the exact layout, spans, and other dimensions involved, I can only offer so much advice. I would think you would be fine to run two 1/2" carriage bolts through the 6x6 and double 2x8 girder. Even better would be to do that, AND simply add a 2x6 vertically to the side of the post, under the girder for support. Even better than that, would be to notch the 6x6 in 1 1/2" to support half of the girder, then add that same vertical 2x6 mentioned previously...thereby supporting the entire 3" width of the double 2x8 girder. Now remember, if you do a girder butt joint at the post, to bolt BOTH ends with 2 bolts each. Also, try not to have both 2x8 butt joints land together if possible. Meaning, stagger your butts in your double 2x8 girder. Now...of course, the best way that comes to mind (again, without seeing the exact layout of course...), would be to make that particular footing nice and wide, and put your 4x4 post right next to your 6x6, and do your usual 4x4 girder thing, then fasten both posts together to boot.

Hope this helps and let me know how you make out, or any other questions. :)


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Michael Romano


I can answer any questions relating to decks, porches, exterior stairs & railings, walkways, access ramps, pergolas, deck roofs, screen rooms, etc... These may include design ideas, footing to framing design & construction methods, various species of woods vs. composites & pvc/vinyl materials for decking, skirting, or railing applications. I also have expertise in various rain-free systems for under-deck storage & living spaces.


I have designed and built decks and many other types of outdoor structures for over 25 years for my own home improvement company. We also perform many other types of home improvements, including window & door installation, molding & trimwork, siding, basement finishing, siding, etc. Our main love however, is decks!

NADRA - The North American Deck and Railing Association. Several Small Business & Home Improvement Contractor Alliances & Associations.

I have written several articles over the years for,, and many other deck & construction related websites.

High School graduate. 2 years of Mechanical Drawing & Architecture classes. Vocational School graduate. 2 years of Construction Technology & Carpentry classes. Many years of reading, researching, and application in the real world.

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I am certified by several decking manufacturers for expert application & installation of their products.

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Mainly local residential clients, and occasional commercial clients, including restaurants, nightclubs, office buildings, etc.

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