Any carpenters here?

[Xithras]

I'm having a debate with a friend and need some help.

As part of my backyard makeover, I'm building an attached pergola to cover my tiled porch. The construction method being used for the pergola is fairly simple: I'm placing a pair of pressure treated 4x4 uprights at the outer edge of the patio, with two 2x6's running between them (i.e. the four by's will have one 2x6 at the top on the yard side, and another 2x6 on the house side, sandwiching the tops of the 4x4's between the 2x6's). This structure will then be attached to the house by six additional 2x6's running between the outer wall of the house and the inner 2x6 on the outer support structure.

Here's my issue: My tiled porch is 17 feet long. Assuming that my 4x4's are placed a foot in from the edges, I'll end up with a 15 foot unsupported span between them. I believe that the structure will work...since it carries no load the 2x6's only have to carry their own weight and a portion of the weight from the attached crossbeams, we shouldn't be anywhere near the failure point of the wood. To test my belief, I went to Lowes yesterday and picked up the end of a 20' 2x6. That 2x6 supported its own weight without any sagging issues.

My friend, on the other hand, thinks the 15 foot span is too long and insists that it will cone crashing down the first time the wind blows. He wants me to add another support pillar in the middle, which will ruin the view out of my living rooms picture window.

So who's right?

[Longhorn]

1. I'm a carpenter's wife

so I asked my husband (remodeling contractor for nearly 30 years.)

He says it won't come crashing down but it could sag over time. What he thinks you should do is take some 4x4 blocks and bolt the 2x6's together through the 4x4 blocks every two feet, 24-inch center, using 7-inch bolts, washers, and nuts. This will give you a beam. He also says be sure to use joist hangers to connect the 2x6 joists to the beam.

Hope this helps!

[Xithras]

2. How stable would that be?

I constantly have lots of kidlets running around my house, so it's only a matter of time until one of them gets the bright idea to climb this thing. By building a beam on top of the 4x4's, I'll be increasing their weight load. How would that affect their stability when being climbed, buffeted by high winds, or shaken during a quake?

[Longhorn]

3. Update.

Mr. Longhorn says that the outer 2x6 in your plan is not bearing any load or adding any strength to the structure if it is not attached to the inner 2x6, which is bearing all of the load (the six 2x6 joists.) His suggestion to bolt the outer 2x6's together with the 4x4 blocks is to distribute the load to the outer 2x6, making the inner 2x6 less likely to sag over time. He says the weight of the additional 4x4 blocks used to connect the 2x6's is minimal, especially compared to the increased strength of the resulting beam. And be sure to include cross-bracing and/or gussets to stabilize the structure.