Porch posts

[bill1952]

Hate to ask this kind of question but can't find answer in IRC.

Existing is 4 bays of wrap around porch and addition is about 14 x 8 with 3 new posts supporting roof.

Question is attaching posts to floor. Is it necessary? The installation instructions for the posts don't show it, and warranty for them require plinth. I worried about wind uplift. Existing are toe nailed without plinths. Thought about anchoring a chain or something in post through a hole in porch and anchor under.

I had no success in attaching a PDF so install instructions are here: https://www.hbgcolumns.com/wp-content/uploads/2025/08/Wood_Post_Installation_Instructions-EN.pdf

 

[TheCommish]

Post, beams above, rafters above the beam all must be able to support all the loads imposed on them, including wind, snow, dead, gravity and up lift. Found in the beginning oc chapter 3 of the IRC R301.1

 

[Gregg Harris]

Hate to ask this kind of question but can't find answer in IRC.

Existing is 4 bays of wrap around porch and addition is about 14 x 8 with 3 new posts supporting roof.

Question is attaching posts to floor. Is it necessary? The installation instructions for the posts don't show it, and warranty for them require plinth. I worried about wind uplift. Existing are toe nailed without plinths. Thought about anchoring a chain or something in post through a hole in porch and anchor under.

I had no success in attaching a PDF so install instructions are here: https://www.hbgcolumns.com/wp-content/uploads/2025/08/Wood_Post_Installation_Instructions-EN.pdf

Use a Strong-Tie plinth that allows you to bolt to deck

 

[ICE]

Are these supposed to be structural or decorative? They do not appear to be structural?

 

[Inspector Gadget]

Canadian codes
9.23.6.2.
Anchorage of Columns and Posts
1) Except as provided in Sentences (2) and (3), exterior columns and posts shall be anchored to resist uplift and lateral movement.

Given as many of our Codes replicate those south of the border, I'd be surprised if similar language didn't exist in US codes.

 

[bill1952]

Are these supposed to be structural or decorative? They do not appear to be structural?

I'd call them structural. Manufacturer says the comply with IBC requirements. Rated for 5800 pounds. The one with largest tributary area is only 3500 pounds (and that's silly because there will never be 60 PSF of snow on this roof). Posts with headers on them supporting roof.

 

[bill1952]

Post, beams above, rafters above the beam all must be able to support all the loads imposed on them, including wind, snow, dead, gravity and up lift. Found in the beginning oc chapter 3 of the IRC R301.1

Thats clear but seems performance based not prescriptive. I was looking for prescriptive requirements. I did determine I'm between the 105 and 110 wind speed isobars. It is a hip roof so some advantage there. The much larger existing porch has been there for 35 years.

Ultimately I'm a little more concerned by the posts not moving and not depending on railings for that. I'd hate to lean against a post and push it off the edge of the deck. I may skip plinths and toe posts into deck, even if manufacturer says I have to use the plinths.

I did look at other plants - like Simpson - but they all look like crap and don't match what's there and I'm trying to match. Meanwhile looking at a plan for a "pin" across post and hold down through deck.

And no help from manufacturer customer service.

 

[steveray]

Thats clear but seems performance based not prescriptive. I was looking for prescriptive requirements. I did determine I'm between the 105 and 110 wind speed isobars. It is a hip roof so some advantage there. The much larger existing porch has been there for 35 years.

Ultimately I'm a little more concerned by the posts not moving and not depending on railings for that. I'd hate to lean against a post and push it off the edge of the deck. I may skip plinths and toe posts into deck, even if manufacturer says I have to use the plinths.

I did look at other plants - like Simpson - but they all look like crap and don't match what's there and I'm trying to match. Meanwhile looking at a plan for a "pin" across post and hold down through deck.

And no help from manufacturer customer service.

It's prescriptive...just no one wants to do the math...

 

[bill1952]

It's prescriptive...just no one wants to do the math...


View attachment 16285

That is pounds "per connection" so does it make sense that for these posts I just add up the "tributary" number of connections? I come up with 64 pound per connection and there are 5 rafters on the portion of the header this post supports - worst case - so connection at top and bottom of post is for 320 pounds? Shouldn't be too hard to design for. Quickly find withdrawal of a 1" no 10 is over 100 pounds.

Thanks for pointing me to this table. I've used hurricane clips or more recently Timberlok screws in rafters and believe In way over minimum. Helps to live where wind speeds are not great compared to many places.

 

[bill1952]

I meant to add finally got manufacturer to communicate. Their answer: Weight of roof and post will hold it down. And they're in southern Alabama. Go figure.

 

[steveray]

That is pounds "per connection" so does it make sense that for these posts I just add up the "tributary" number of connections? I come up with 64 pound per connection and there are 5 rafters on the portion of the header this post supports - worst case - so connection at top and bottom of post is for 320 pounds? Shouldn't be too hard to design for. Quickly find withdrawal of a 1" no 10 is over 100 pounds.

Thanks for pointing me to this table. I've used hurricane clips or more recently Timberlok screws in rafters and believe In way over minimum. Helps to live where wind speeds are not great compared to many places.

<200# uplift you can use prescriptive rafter nailing...But yes....Add the uplift on the span and divide by 2 (for each beam bearing) and Uncle Bob is your uncle....

 

[Inspector Gadget]

I meant to add finally got manufacturer to communicate. Their answer: Weight of roof and post will hold it down. And they're in southern Alabama. Go figure.

This is why Codes exist. Because nobody wants to do the right thing on their own.

 

[bill1952]

Just finished putting posts up. 4- 2" #10 SS FHWS into post (albeit end grain) and 2 - 1/4 20 through deck. 3 post support a hip roof - approx 50' SF. The numbers seem to check.

I appreciate and believe in the codes - why I've been active in code development since1987 - and appreciate the help I get here.

 

[ICE]

"Aluminumor plastic plinth is used between post and porch floor"

The plastic base is one thing that caused me to wonder if the setup is structural. I am still not convinced. But hey now, what do I know?