I'm completely lost

Reno Italiano

Here's my problem...I am in the beginning stages if designing and building a patio cover over a concrete slab off the back of my garage. The slab has two support walls (in the shape of an L) that I plan on attaching ledger boards to. the rest of the patio will be open to the yard just using 4x4 posts. The design calls for TWO 2x6 pressure treated ceiling joists (running parallel) 3.5 inches apart, big space, then another two 2x6's , a big space, etc.. My question is...How far apart can I legally place the joists apart from each other? I know if it was just one 2x6 I could place them every 24''o/c, but if it's (2) 2x6's, can I legally place them 48o/c? Any feedback is appreciated. And thank you ahead of time.

Reno Italiano

Here is what I'm trying to build. Hope this helps someone. It's plans call for 16' by 18'. The only difference is that I want to sheath and shingle the roof so I can use it during the rainy season.

vsheetz

Here is my patio cover/pergola, somewhat similar to what you want to do I think. Notice I moved the front cross piece up on top rather than hanging down to keep it from blocking view by using what I call "hanging posts". The span between the double rafters varies on the different areas of the patio and averages to about 36" or so.

http://www.webjeepers.com/homestead.html

Mr Chips

I'm no engineer, but I t hink the fact that you are going to add shingles and sheathing is a game changer. You will need to factor that added weight into the plans, as well as things like snow loads (depending upon where you live)

Ron6519

Agree with Mr Chips. When you modify the structure, you can't use the design shown. You would need to speak to someone with a structural background to design the proper structure for your location.
Ron

Scuba_Dave

How big is your area to be covered?
The span distance will decide how big your beams/joists need to be
Where are you located - snow load, heavy rains?
Are you planning a flat roof?
How far apart will the 4x4 posts be?

Reno Italiano

Thank you for your replies. The roof will have an 8 degree run off and will span a 16' x 18' area. I do live in a rainy and sometimes snowy area so I am concerned. The home owner had built a previous covering that was 12'x12'. He used the same two walls as support but had no ledger beam (header) of any kind and only used nails and a single 4x4 post. It lasted 20 years!!! Shocking!!! Snow fall took it down about 5 years ago due to a heavy winter snow. I will be using a ledger board on both walls and anchored with bolts every 16 inches o/c. My posts are at the end of the patio cover where the rainfall and melt will run off.
Sorry for not clearly understanding, but, I just thought with two 2x6's a thicker sheathing, I'd be able to run each set further apart and still maintain that cool looking construction.
Please help me understand what I should do.

Scuba_Dave

A 2x6 will span around 10', maybe a little more
To span 16' I think you are looking at 2x10's 16" OC
That is with just a corner post at the outer edge of the 16x18 structure. But either way 16' is about the smallest span without posts in the middle of the structure

Without a roof there is a lot less load
Once you add the roof then you need to go much larger

Reno Italiano

Thanks Scuba Dave. Can I show you these?? Hopefully my pics will give everyone a clearer idea of where I'm at in this project.

Reno Italiano

This is what I'm wanting to do. Run every set of 2x6's so that every outside 2x6 is 48" o/c. then lay my sheathing so it is nailed down on every outside 2x6 at 48" o/c. The inside 2x6 of each set would just be added support. Is this possible, or could I be way off the mark and still need a 2x6 every 24"?!?!
Still lost?

Ron6519

The 48" spacing far exceeds the plywood recommendations, any plywood.
Ron

Reno Italiano

Thanks Ron6519. I was worried about that.
Would 36" be safe? Or will I have to place them every 24"? maybe alternate single 2x6 and double 2x6?

Ron6519

Maximum spacing is 24" between supports. Every piece of ply will have the specs on the board.
Ron