Howdie ,I guess I,ve been looking in the wrong places so here I am. I want to put a balcony off the second story of my house, not terribly deep maybe 6 feet but I don’t want to support it off vertical posts to the ground. So I,m looking for the rules for self supporting/cantilevered balconies thanks pgrainger
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Well now Bliss,
Welcome, but it looks like the first thing you'll have to learn is how d'ye spell howdie. I always write my leters back home to the folks with a nice big "Howdy"! howdie just sounds so, "do you mind if I say hello?" So use a nice friendly open "Y" Or you could say it like old Minnie Pearl, "HOUW-DEEEEEEEEEE!"
Now what was I gonna say?
Oh yeah! the cantilevered porch thing. You might not get too many responses to this one because if not done right, it can be a tremendous liability. Porches are dangerous, the more so when elevated and the outrigged ones are most so. So consider this advice as being worth what you paid for it. Disclaimer rules
I'm presuming you have a finished house already, so get ready to tear something up. This is not really a cantilevered job which is where you extend the floor joists out beyond the supporting wall under them. You couldn't practicly and safely do a cantilever six feet out. You will be bolting the deck frame to the house like you normally would
Without legs going straight to the ground, you need kickers, knees, or fancy corbels to lend support to it. Now suppose you go with the simplest way, a fourty five degree kicker running back to the house. It wll land on the wall about halfway or so down. Is there framing there to resist the horizontal pressure that will be generated with a load of snow three feet deep. a pile of firewood or hibachi table, and a frustrated snow shoveling homeowner? Probably not! I rebuilt a support for a bay that had been done that way. One of the two kickers hit a stud while the other was perched against the sheathing only. The whole wall was curved in about four inches in eight feet. So you need to tear up the wall to put in studding that will handle it.
OR
You can run the diagonal kickers at a longer angle all the way down to the foundation. I will try (dang this prospero) to attach a photo of one built that way. It is a pic of the whole for a progress shot so you can just barely see the 4x4 kickers but it might help.
Another possibility would be a cable truss type design but you are going to need onsite engineering for that.
Hello, first time user here. I really enjoyed the picture of the steps and landing. The handrail looks good. What did you use for top and bottom rails, it is hard to tell from the photo. My thought is that 2*4 would not be firm enough. Your answer to the cantilever question was also good. A six foot cantilever would be best engineered and installed at the time of construction, as a add on it woukd definitely be major surgery.
Well all these years of bad spelling, you are the first to point it out to me , I thank you , I think, seems my spelling is a Scottish term for a midwife. Your suggestion of using kickers would work, the forces would be transfered into an 8in concrete wall. My reason for not wanting vertical support was that the grade is level for about 15 ft then drops off so I didn't want to make the narrow strip of level land narrower. THe pool was a good idea but a narrow pool it would be.
I didn't mean the spelling thing as a correction as much as for entertainment.
Now how will you attach the kickers to the concrete? I imagine the kicker will need to be a structutral, truss type corbel and that you will have a PT 2x6 vertical glued and Hilti bolted to the concrete with the butt end al the way down to the footing. That will give you something to fasten to.
Excellence is its own reward!
Build a pool below, a 6' cant. deck would make a terrific diving board. And if it failed, the water would break your fall. I'm with Piffin. Any reason vertical posts won't work?
918 Contracting - Residential Construction
General rule of thumb for self supporting balconies/cantilevers is "one unit of overhang is cantilevered by two units of support". (Exceptions can be designed.) So your 6 ft of balcony would require 12 ft of counter balance for a total lenght of joist at 18 ft.
I am assuming the existing structure will allow you to slide these joist into it in a correct manner with supportting posts to affect the design!?? More details would be helpful.
Keep in mind that these 18 ft joist are continuous from the outside to the inside and can provide a natural pathway for water migration into your houses structure. Attention to detail at this point is critical using this plan.
Piffin's idea is more watertight, but its downside is the control of the horizontal forces generated by the knees.
More info please!...........................................Iron Helix
Iron Helix,
A rule of thumb only works until the thumb turns black and blue. The tag end of yours is up to a limit of twice the depth of the joist. ergo
a set of 2x12 joists could cantilever out two feet, woefully short of the six required here. It won't suddenly fail, for sure, but ten years hence that six feet would have a low hanging tail end, I'm guessing about two inches or so, depending on snow, etc.
That particulat handrail was 4x4 PT posts, top and bottom milled out of two by clear fir with Port Orford Cedar balisters. I often use a rail premilled of PO Cedar but this customer wanted a wide rail and the fir is strong and rot resistent. It got painted the same Essex green colour as the rest of the building. The post caps were from Island Post Cap. The deck surface is Pau Lope`
Let's see if I've got a better shot of it...
Excellence is its own reward!
I thought the "rule of thumb" for twice the depth equals the inches of cantilever refered to cantilevers that had a bearing wall at the unsupporting end........yes/no?
With a plain balcony there is to point load at the unsupported end.................hence my "rule of thumb"........................
Guess maybe an engineer could enlighten...........................Iron Helix
Iron Helix,
You're correct.
For cantilevered joists, the joist can be cantilevered one-third of it's length. A 12' joist? 8' inside the structure, 4' outside the structure.
You seem to be assuming that the deck will bear no more load than the air surronding it. Decks need to be designed for a sixty pound load. Living space is only fourty. Some roofs are only fifteen while others arre seventy. It depends on the area of the country. In the north, you get quite a snow load. In Florida or San Diego, you get quite a party load of human flesh. The latter is why the newspapers have an account of deaths due to deck failure every year.
So you need to design for the load.
Excellence is its own reward!
a nice set of breaktime blueprints sure would take out the guesswork.......
but ditto for design by specific loading.............................Iron Helix
Piffin,
That garage/hideout is exactly what I want to live in when my wife divorces me. Add a couple more bays. Throw in a few Harleys, a toaster oven, fridge and beer tap. Honey... I'm home!.... I have a Yellow Lab named Honey.
We once added a 4 ft cant. addition to a lake house. This project was engineered but still had me wondering about whether it would work or not. It did. Water intrusion wasn't as much of a concern as the exterior wall was moved out to the end of the cant. I'm not going to list all the methods used as I'd hate to forget one. Get it engineered, be concerned with proper (good luck) flashing techniques and best of luck.
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Remodeling Contractor just outside the Glass City.