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I have an aging cedar deck I'd like to add a small pergola to for use this summer, maybe next, before I replace the deck with something new (probably composite Trex).

I think I have a simple design I like but I am a little baffled on how to safely attach new posts to the existing deck. I believe what I need to use are post anchors but can they be safely attached to the cedar planks near the joists or do they have to go into the existing posts?

Also, is there a major difference in post anchors? Prices seem to be all over the place. Is something like this https://www.thedeckstore.com/tisan-aluminum-post-anchor.html what I want? I like that it is nearly invisible. Or do I need something like this? https://www.homedepot.com/p/Simpson-Strong-Tie-E-Z-Base-Black-Powder-Coated-Post-Base-for-4x4-Nominal-Lumber-FPBB44/100655350

Or am I just looking at the wrong thing entirely?

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    Does this answer your question? Can I build a pergola on an existing deck, without digging more footers?
    – TylerH
    Jan 5 at 20:37
  • See also diy.stackexchange.com/questions/119389/… and many of the other posts on the right-hand side of the page under "Related".
    – TylerH
    Jan 5 at 20:38
  • Appreciate the comments. I did see other similar questions but no definitive answer on what I should use? The pergola should not be particularly heavy, I am confident the current cedar deck can support the weight. I am more curious how to actually attach it :)
    – mikeds
    Jan 5 at 21:14
  • Even though lumber prices have dropped, they're still much higher than 2 years ago. Why spend that much on lumber for a temporary pergola for 2 years use then tear it out? Put the money in the bank for a year and put it toward making the deck upgrade sooner.
    – FreeMan
    Jan 6 at 15:30

1 Answer 1

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There are four issues: 1) Holding the pergola up, 2) Holding the pergola down, 3) adequate attachment to the pergola and deck , and 4) appearance.

  1. Establishing the weight of the pergola is key to this step. You indicated it is a “small pergola”. So, I’ll assume it’s about 8’ x 8’ x 8’ high. Depending on materials used, this would translate into about 700 lbs. if there is no floor in the pergola. That weight distributed to four posts equals about 175 lbs. to each post.

2x decking cannot support such a load. The posts must be anchored to beams or footings below the decking.

  1. Uplift is determined by calculating the wind uplift minus the weight of the pergola. Uplift is about 25 psf where you live. So, net uplift is 25 psf x 8 x 8 = 1600 lbs. - 700 lbs. (weight of pergola) = 900 lbs.

Again, 2x decking cannot support such a load. The posts must be anchored to beams or footings below the decking.

  1. An adequate post support might look like this: Simpson PA strap tie, because it’s strong enough and long enough to extend down to a concrete anchor ( 150 psf x 1’ deep x 3’ x 3’) sufficient to hold it down and adding a post under each leg could hold it up…but it looks industrial.

https://www.buildsite.com/pdf/simpsonstrongtie/PA-Strap-Tie-Holdowns-Product-Data-1462031.pdf

  1. Having a minimal looking connection will enhance the appearance like this: Simpson CPTZ.

https://www.amazon.com/Simpson-Strong-CPT66Z-Galvanized-Concealed/dp/B00KYVWQNY/ref=asc_df_B00KYVWQNY/?tag=hyprod-20&linkCode=df0&hvadid=198090962560&hvpos=&hvnetw=g&hvrand=8722853821112891294&hvpone=&hvptwo=&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=9033035&hvtargid=pla-542057085992&psc=1

It is a concealed anchor and will look better. However, it needs the same post extension under the deck and concrete anchor in order for it to work.

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  • Excellent, thank you for the detailed answer. This is exactly the info I was looking for. So obviously attaching to the planks is out. I believe I can make adjustments (it is a super simple design- posts, joists, lattice) so that the pergola posts meet at existing posts for the deck. Then hopefully I can just tie directly into those?
    – mikeds
    Jan 5 at 21:48

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