posted
got an install problem i've never been up against before.
3 4x8s freestanded mounting to form 1 8x12. bottom must be 4' above grade. i'm using 1/2" econolite. should be installed to last a while. any suggestions are appreciated.
-------------------- leonard gorsky signcrafters 15178 willow wood lane 530-273-1494 signs@gorsky.org Posts: 30 | From: Grass Valley, CA 95949 | Registered: Jul 1999
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with that many seems, you'll need some kind of frame. Perhaps your local iron-worker can fab something up for you. A decent frame could be mounted between treated 6x6s in concrete.
-------------------- Glenn S. Harris
....back in the sign trade full time. Posts: 293 | From: Baton Rouge, LA, USA | Registered: Jul 2001
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posted
Leonard, if you have the time, you might want to invest in a good installation book. 96sf with just a 20 psf wind load is almost 2000 pounds of force that you have to get to the ground. Some good books have been mentioned here in the past. You might want to search the archive to see what you can find. Vic G
-------------------- Victor Georgiou Danville, CA , USA Posts: 1746 | From: Danville, CA , USA | Registered: Dec 1998
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posted
my lawyer won't let me make that call for you... but I have a feeling you'll need a lot of "econo-heavy" factored in there somewhere.
I would expect to have at the very least six 4x4 posts buried 24" in the ground. (possibly with cement) If it were MDO I would not bother with any horizontal supports for structure (just to upsell the appearance if necc.), but I never used econolight, so I don't know if it can hang 18 - 24" out past the post & hold up to high winds. I would expect to include a 2x4 diagonal brace back off each post & secured to the ground by nailing in a 24" steel stake (like used building concrete forms) I guess both seams may also need some narrow splice pc. to keep the face in the same plane.
posted
thanks for the advice. i was thinking about 3 4x4s, but now i'll go for 6. concrete and back supports. on anchoring the back supports, how does one attach the 2x4 to the stake? and would 4 4x6s be as good as 6 4x4s? and i'm leaning (ha, ha) toward horizontal 2x4s for matching and more fastening surface.
econolite is a fairly new product, a mdo replacement. its 1/2" thick of very strong, rigid corrugated plastic, weatherproof, sandwiched between 2 sheets of aluminum, 1 finished. it is stronger and lighter than mdo.
i've been in this business for 20+ years, and there's something new every week.
-------------------- leonard gorsky signcrafters 15178 willow wood lane 530-273-1494 signs@gorsky.org Posts: 30 | From: Grass Valley, CA 95949 | Registered: Jul 1999
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posted
if you went with 4... 1 on each joint & 1 on each end, I would agree that horizontal supports should make up the difference. I also agree that a 4x6 would be a worthwhile upgrade assuming the 6" goes front to back & actually adds to the direction the wind is trying to snap it.
The stakes I'm talking about have holes through them, so you can nail in to your brace, but you can only get one nail in that way. That would only come into play if the wind is trying to blow it down forwards, so angle the stake in going forawrd (perpendicular to the diagonal brace)
posted
When it comes to engineering this structure, what is the legal requirement in the area? The city or county code may specify that the sign stand up under a 30 PSF wind loading. Some areas require 20, some coastal areas spec 40. The design wind loading will drive the final selection on post size, quantity and embedment.
As far as the question of whether four 4 x 6 posts would be as good as six 4 x 4s, the answer is yes, providing the posts are installed with the long direction perpendicular to the wind load. Actually, four 4 x 6 posts are approximately equivalent to eight 4 x 4s. This is assuming full 4" x 6" and full 4" x 4" dimensions.
The manufacturers of Econonlite may have a tech manual that gives recommended bracing and engineering specifications that would be helpful to you.
-------------------- David Harding A Sign of Excellence Carrollton, TX Posts: 5106 | From: Carrollton, TX, USA | Registered: Nov 1998
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posted
The 10mm Econolite would be much stronger than the 6mm in this situation. You might do a search in the archives, seems like I remember someone having problems with the thin silver backer on the Econolite when exposed to weather.
-------------------- Mark Perkins Performance Signs & Graphics Eunice, Louisiana "The heart of Cajun Country" Posts: 506 | From: Eunice Louisiana 70535 | Registered: Nov 1998
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posted
Hope your install went well. I haven't been on the board all week to offer any advice. Sorry.
I would never use less than 4x6 for that much wind load. Econolite (they've fixed the backer problem) and alumalite will take more windload than your minimum code requires if properly attached. Laminators will send you an installation guide for all their products free. It is very helpfull.
Basically, you need to attach these panels around the perimeter. I always make a pressure treated 2x6 frame. Usually in this case, I would use 4 6x6's, not just for strength, but also for better rot resistance. With this size, concrete or extra support is not necessary as long as you can dig the holes deep enough. One third of the overall length of the 6x6 needs to be in the ground. Any less than this you need concrete to add ballast and/or extra holes with support rails.
In your case, 4 eighteen foot 6x6's, with 6 feet of the pole in the ground would suffice. 4x6's would work for a sign not as high or in dry soil.
Run 12 foot 2x6 treated across the top of the 4 poles and another rail just under 8 feet from the top. Now run 2x6's against the poles between the rails to make a flush frame. I attach #12 stainless steel pan head screws every 24" around the entire sign. On really high signs with more windload I go 16" apart.
I have an alumalite sign that is 30 feet to the top that took a direct hit by a small tornado, probably F1. It ripped the roof off the lumber yard building next to the sign. This particular sign had steel 8x8 wide flange beams with 2x6's attached with bolts. The tornado twisted the 2 steel beams slightly, but the alumalite panels all stayed on the structure. It was an 8'x8' upper portion, a one foot gap, then a 5'x14' lower portion. So when Laminators says their panels will withstand 120 mph wind when properly attached,I believe them and I can now show proof.
I decided to edit this post regarding 4x4's for signs. Remember, just one good sized knot in the wrong place, mainly just above ground where the most stress is, will considerably weaken a wood post. 4x4's are fine for 4x8 and smaller signs, but for multiple panel signs, 6x6 are much stronger, much more rot resistant, and better looking. The customer is paying for the poles, so if they balk at the price, ask them how willing they are to test their liability insurance. I won't test mine!
[ October 04, 2003, 04:56 PM: Message edited by: Dave Sherby ]
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