Since this thing won't carry anything heavier than a wind chime I think it will work, but I want to make sure it isn't going to come crashing down on me if I try.

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I think you should be fine. I don't know of any engineering charts for that type of structure since there is basically no load. The closest may be a chart for ceiling or even rafter joists but they account for a load.

Do you want this structure to looks good too?

If so the way you want to install the 'stringers' may look the best but by doubling them up without spacers and setting them right on top of the posts will be stronger and help prevent twisting.

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I was thinking that my spacer idea would give it a structural strength nearly equal to doubling the wood up directly. By slipping 6" tall 4x4 spacers in between the 2x6's at several points, and then securing those spacers with bolts through both the 2x6's and the spacers, I should be creating a "box" effect which should make it behave more like three 5 foot spans than a single 15 foot span. These shorter "boxes" should make it fairly twist resistant.

Of course, my biggest worry is sag, not twist. My statement that there would be no load wasn't entirely correct because this beam-pair will carry weight from both the crossbeams extending outwards from the house AND from the smaller 2"x1/2" slats that will overlay the whole thing. By my math, these beams will carry about 75lbs of load at their centerpoint in addition to their own weight.

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Since you are not putting much load on it the method you suggest will work. However I am uncertain about sag. Let's see what 2X thinks. He may have more experience with this type of structure.

For sure it would look better your way Drak, and looks has a big factor in that type of structure.

Another thought is use a single 2 X 10 or 2 X 12 to prevent sag.

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The "twist" you mention is often caused by wet wood. Go to the extra effort to buy KILN DRIED lumber or Pressure treated wood that has set for a while. I guarantee if you buy it sopping wet like they sell it at home depot it will warp like hell. I typically don't cantaliver more than 24" or 2 feet.

If you were to do something like this I would step up to 2 x 8's to support all the additional weight up top.

The span on my project is 18 feet.

It turns out I may have another problem though. I was told yesterday that I have to pull a building permit for this thing, and the California Building Code specifies a maximum unsupported beam length of 12 feet without steel reinforcement to prevent earthquake related failures. Since I don't live in an earthquake zone, that leaves me with two choices: 1. Ignore the law and build the thing how I want it knowing that it will be fine. 2. Pay the city several hundred dollars in fees and redesign the entire structure to meet a building code designed for natural disasters that don't occur here.

At the moment, I'm leaning towards number 2.

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If it's as small as you say it's only a couple of hundred dollars to build. I'd say F the police and build it. The worst anyone could say is "sorry you have to take it down"

If you can avoid attaching it directly to the house you would avoid a number of potential problems. Rather than attach to the house just use four 4 x 4 post to support it.

quote:

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Originally posted by Drako:
Quis est porro intolerabiliter span EGO can tutus constructum per iugum of 2x6 ligamen in a non - sarcina gestum compages? I'm aedificium edificium a umbra compages in meus tergum yard quod volo a 15 pes patefacio span inter meus 4x4 rectus. EGO teneo ut wood can suscipio torqueo ut pieces adepto diutius , sic EGO eram reputo ut I'd run duos of lemma ( unus in utriusque of rectus ) quod locus unus vel duos tractus inside ut servo lemma quadratus per invicem quod proventus suus austerus. Utpote is res won't veho quisquam graviter quam a ventus chime EGO reputo is mos opus , tamen Volo facio certus is isn't iens ut adveho fragosus down in mihi si Conor.

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Good luck. Post pics when its done.

[ 06-01-2005: Message edited by: Flux ]

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Close. Latin.

[ 06-02-2005: Message edited by: Flux ]

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Just remember, if you're ever in my back yard when an earthquake hits, run for the lawn or get inside the house

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