[fatboyracing]

I am in the planing stage for a covered patio going over our concrete pad.

I have no clue how to figure out what size post to use

it will be 12ft deep and 18 wide

We are using factory built truss that have a 4/12 pitch

the beams running out to the house are going to be lvl beams that are 1 1/4 x 9in

The beam that runs the 18 ft span I guess will be another lvl beam

I have no clue how to find out what size post

 

[rander101]

It'll take a bit better description of what you have in mind. What is your planned ceiling height? How are the posts to be anchored; buried in ground; on a footing with metal anchors? which way will the trusses span; 18ft or 12ft .

Have you checked your local building code?

 

[lenaitch]

You need to be guided by your building code. Your description mentions beams running out to the house which makes it an attached structure and I don't know if LVL beams are rated for exposed construction. You also need to consider the footing structure for the posts.

 

[ront02769]

Post size nominal six bye six will do it. Ron

 

[bob22]

I'm a bit fuzzy on how you are moving forward on this since you apparently have no idea what design specs are needed yet you have purchased other materials. How do you know the trusses are appropriate for your situation? I'm not trying to put you down and applaud your efforts in asking a question on the posts but perhaps other questions on other materials used need to be asked as well.

 

[Daniel Holzman]

There are really only a few ways to design a project. In your case, the project includes sizing various structural elements (including the posts which you inquire about), beams, joists, rafters, that type of piece. So you can develop your design at least five different ways:

1. Follow code. Simple, generally conservative, recommended.
2. Develop element sizes using engineering principles. Requires advanced structural knowledge, generally results in a less expensive structure than simply following code, however you have to pay for the design if you can't do it yourself.
3. Copy a design from another project that worked out acceptably. Downside is you have no idea if the design is any good or is cost effective. Advantage is you don't have to pay for plans.
4. Use rules of thumb. Effective for simple elements, works if the rules of thumb are adequate. Downside is you rarely get the most cost effective design, and you have no real idea how strong the structure will be.
5. Guess at the right size. Not recommended, but surprisingly common.
6. Solicit help from someone who has built something similar. This can work out well, but again you don't know how good the design is.
7. Get help from an internet chat forum. May be OK, hard to evaluate the quality of the advice you get.

In your case, I recommend you discuss the project with the local building inspector, they may be willing to direct you to code section specifying post size. There are on line calculators that may be used to estimate post capacity, if you know how to estimate vertical load on your structure, you can calculate the load on the posts, and figure the minimum post size. Make sure you check your post for buckling, that normally controls. Also understand that you have to get all the pieces to lock together, so you may need to notch posts to accept beams.