Hello All,
I am building a 36′ long by 12′ wide deck and need to know about cantilevering the joists. I have looked through code books and such and can’t find the info. The 2 x 10 CCA SYP joists will sit on a ledger board at the house. The outboard ends will sit on a built up beam on 6 x 6 posts 9′ out from house. Can I carry them another 3-4 feet out from the beam on a cantilever. I guess does the 2/3 in 1/3 out rule apply?
Thanks in advance.
Cole
Cole Dean
Dean Contracting
Replies
Try this article from the JLC website:
http://www.jlconline.com/cgi-bin/jlconline.storefront/3d41ece8001f65e8271a401e1d290632/UserTemplate/82
Good Luck,
Don Wood
Yeah thats the rule I am familiar with.
2/3 in 1/3 out. Never heard it that way, but it is the same as the rule I follow for every 1 foot canted out 2 feet under. 2:1
Jeff
Just because it's a rule doesn't always make it desireable. deflection might be a consideration too.
Right I was merely stating a general rule of thumb, not to be taken as a matter of fact. The when it fails sue me because of my post on the fact. This is a message board take it as you will, ideas are given and taken. Hopefully people can think for themselves( but we know they can't). If in doubt consult a professional! Thanks Jeff
What spacing are these 2x10s gonna be on? What type loading beyond the beam - benches? Built in planters? What type rim joist? What grade are the joists?
That rule of thumb(2in for one out) is not an enshrined engineering formula. I would use it for a simple deck if there were no loading on the outer portion beyond people and the rail. If a roof were to load onto it, that would scare me.
Also, you mention that the joists would perch ON the ledger board rather than butting into it with toenailed hangers. What will keep them down so they don't want to flip up when ten guests all rush to the rail to see something? When you are cantilevering, you need to design for that uplift as well as down load.
Thank you all for your replies. I should have given more information. The joists will be on 16" centers and will be installed on the ledger with hangers. I actually remember reading an article in FHB by Mike Guertin about framing a cantilever bay and he turned the hangers upside down and wrapped them over the top of the joists to prevent uplift. I considered doing that with every other joist, but am still researching that.
The interesting thing about this project is the deck I removed was 53' long and 6' deep. The length of the house, to wash windows etc. The joists were 2 x 6 untreated pine sistered to the floor joists in the house. Funny part was they extended into the house 2' and extended out of the house 6'. Absolutely no posts or other support under the outboard end of the deck, and this deck is 8' off the ground. All of the pine was rotten and the deck pretty much removed itself.
The only loading on this deck will be people and the rail, but the rail is going to be steel with 2.5" top and bottom rail, and 1.5" balusters. All welded together.
Again thank you for your help.
ColeCole Dean
Dean Contracting
The cantilever rule of thumb of "one out/two in" is typically applied only *IF* the design of the cantilever works.
You have to design the cantilever for bending, shear, unbalanced loads, and deflection first. Then you apply the "one out/two in" rule of thumb to determine how far back to run the cantilevered material.
Right now I am having amnesia and deja vu at the same time. I think I've forgotten this before.
Well, I'd say it's borderline, Cole. I'd use a 2x for rim joist across the ends of those things and block between them where they cross the beam. Still, I'd prefer to move the beam farther out from the house and let the 2x10s span farther between the beam and the house, with less cantaliever.
Maybe I'm too conservative - it's hard to imagine a 2x10 flexing much as long as you keep it plumb...but it just seems like an unnecessary risk. How would you ever correct it if it did start to fail?
Brinkmann for president in '04
Cole, to the uplift question: Check into I believe the Simpson H6 . The hold down ratings are good. It's a flat hold-down with a twist. You would be fastening to the side of the joist and to the face of the ledger, if you use that method at the house connection.__________________________________________
Remodeling Contractor just outside the Glass City.
http://www.quittintime.com/
For uplift problems where the joists are hung off a ledger -
Try putting a second joist hanger upside down on TOP of the joist.
Credit cards? It amazes me that people can dig themselves into such a deep hole with such a little piece of plastic
If youre at all worried as I always am .....being an over-doer........ is to just add three more footing close to the end of the deck and run dbl 18' 2x12 or whatever over 4x4's just for added protection.... if it helps you sleep better at night, beyond the cant....Won't add all that much more cost.......Under $200 and a half a day for you alone.......depends what your getting paid for the job.
Be well
Nmaste'
Andy
It's not who's right, it's who's left ~ http://CLIFFORDRENOVATIONS.COM
I think the problem with words, is the create an image . Everyone has a different Image for the same question.
I never considered the point piffen made about a snowload. I think it would take a hell of a lot of snow to tip up a deck that was bolted and has joist hangers, Installed. Although, the older you get the more you see. You never know it all. Especially, if you can't remember what you've learned. LOL
As i've heard said, "youth is wasted on the young" ,right piffin. Or as they say it around here "too soon old, too late smart". lol
If you have all your framing members strapped down properly, Including the beams which are bolted to the sono tube concrete piers. I can't imagine a problem. How long a warranty do you want? i like the idea of turning the joist hangers upside down. It's creative, Except I think you have a greater chance of it tipping down than up. It's only the teco nails holding it either way.
If you are realy worried about it. Why not put a 1 1/2 " ledger strip, top and bottom , lag it to the main ledger. Notch you joist ends, to rest, top and bottom.
*Only thing to remember : If you notch the bottom of the beam the load carrying ability, is now rated for the width of the joist from the notch up. In otherwords: You 2 x 12" with a 1 1/2" notch on the bottom now becomes a 2 x 10". And so on.
A combo of Joist hangers and a top ledger flush with the deck might be the key. If you are worried about it.
Thanks guys,
I am not overly concerned, but I do enjoy a good nights sleep. Of course, the last course of decking will tuck under the 12" lap siding. So that 5/8" of coverage over that last course will keep it from tipping up. JUST KIDDDING.
I think I will frame it up with a 3' cantilever, turn every other joist hanger upside down, use tico clips on the sides, block the joists out at the beam per Mr. Blodgett, and deck it. After I'm done, if I don't feel 100% secure about it I can pour some more caissons and add some 6 x 6 out at the front. I'll take some pics next week of the progress and post them and if you feel like it you can comment from there.
Thanks for taking the time to address my question. I know structural questions can bring a wide array of answers, depending on the conditions, so thanks for taking a shot at it for me.
ColeCole Dean
Dean Contracting
" turn every other joist hanger upside down"
That isn't what I meant at all, and I don't like the idea. I meant add a second joist hanger upside down on each one.
"If I melt dry ice, can I take a bath without getting wet?"
watch your load out their I' ll bet you it will warp down in a few years if you have any load on it. no matter what the charts say! 15 years of trial and error wont lie!
Edited 7/28/2002 9:14:37 PM ET by Frame Boss
Use lam joists / beams then.......are we worried about terrorists doing a number on our decks?....lol....sorry, couldnt help myself
Be well
Namaste'
andyIt's not who's right, it's who's left ~ http://CLIFFORDRENOVATIONS.COM