Advice for Pergola built on existing deck

Reply

  #1  
Old 10-01-18, 03:21 PM
O
Member
Thread Starter
Join Date: Oct 2018
Location: USA
Posts: 3
Received 0 Votes on 0 Posts
Advice for Pergola built on existing deck

Hi everyone. I've built a pergola on an exiting deck and I'm looking for some opinions on how I attached my post bases for safety. I'm at a point where it would be quite easy to take it apart and re-do anything that is unsafe or wont work so it's a good spot to ask for advice before finishing it with a roof. Here's the brief:
  • Existing 12x10 cedar deck is built on treated 4x4's sunk in concrete. It's actually pretty overbuilt as it has 8 posts
  • I mounted the 6x6 Doug Fir pergola posts using Simpson posts bases with one 8"x1/2" lag bolt through the 1" cedar deck and directly into the top of the 4x4 ground contact post under it. I added another two 4" lags through the Simpson base to help secure it and stop rotation.
  • The pergola is 2 6x6x7' posts with a 6x8x12' beam supporting 7 2x8x16' rafters firmly secured to the house with a lagged board. The post and beams are secured with Simpson 6x6 steel right angles and lags. Hurricane ties secure the rafters at the beam end and hangers on the house end.
  • The entire structure is pretty solid so far, but at the post end I can induce about 1"-1.5 of sheer if I rock it really hard. The separation from sheer is occurring mostly at the beam/post attachment and a little at the post base.
  • Next steps are 6x6 36" 45 degree knee braces on both post/beam connections as well as integrated perlons. Both of these will shore it up pretty nicely. I'm also considering adding knee braces to the bottom pf the posts attached to the deck to shore it up on the lower level
  • The pergola roof will be Suntuf polycarbonate and subject to snow load. I'll also be mounting plastic weather curtains all around. Both of these will increase issues of wind inducted sheer.
So... the big question: Did I mess this up from the start by not sinking the 6x6 posts through the deck? I considered cutting off the existing 4x4 posts and using the remnant in the cement to lag the Simpson post base in to. I'm hoping that I can get away with not having to pull out the old cement foot and sink the new posts etc. That seems like a bit much but I'm hoping for a more educated opinion and I'd love it if what I've done works but also ok with rebuilding as it's only maybe an hours work to pull it apart right now and I want it to be safe.

Couple of pictures attached. Thanks in advance!
 
Attached Images    

Last edited by ozzyblue; 10-01-18 at 04:22 PM. Reason: Correcting numbers
Sponsored Links
  #2  
Old 10-01-18, 06:02 PM
XSleeper's Avatar
Group Moderator
Join Date: Dec 2004
Location: USA
Posts: 25,855
Received 644 Votes on 596 Posts
Current codes in most places call for 6x6 under decks, not 4x4s but it's a little late now.
 
  #3  
Old 10-02-18, 08:35 AM
O
Member
Thread Starter
Join Date: Oct 2018
Location: USA
Posts: 3
Received 0 Votes on 0 Posts
Good to know. I didn't build the deck so just working with what's there.
 
  #4  
Old 10-02-18, 10:46 AM
czizzi's Avatar
Member
Join Date: Jul 2007
Location: USA
Posts: 7,388
Received 14 Votes on 12 Posts
Is that last board attached to the gutter? How are the balance of boards attached to the house? Yes, cross bracing will take the sway out. At his point, the problem will be down the road when you have to change out the decking. As the structure sits on the decking and is bolted through it, you or someone else will find it a challenge.
 
  #5  
Old 10-03-18, 08:30 AM
O
Member
Thread Starter
Join Date: Oct 2018
Location: USA
Posts: 3
Received 0 Votes on 0 Posts
@czizzi thanks for your comment. No the last board is not attached to the gutter and the rafters are attached to the house with hangers fixed to a 2x8 lagged to the spanned structural beam on the 2nd story. Rock solid.

I think your comment on the decking is the most compelling reason to re-do the post attachment, I hadn't thought about having to replace them but yeah, that would be a massive pain in the a$$. FWIW I met with a contractor yesterday who said that what I've built is totally fine but he had the same concerns about long term deck replacement. He also noted that it would be quite difficult to replace the existing ground contact 4x4's on the deck posts years down the line when they've suffered from rot.

So I've made the decision to go with the original plan of continuing the pergola posts through the deck and attaching the Simpson post base to the existing concrete pad. I'll be a few hours extra work but worth it for peace of mind.

Thanks!
 
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: