Minor Cantalever Issue

[Ralph Brady]

Gotta love those rural properties. Homeowner, electrician, plumber, balcony builder.

This house was off-the-grid with a 10 amp 120V AC converter!

Attached with regular joist hangers!


Very nice view though.

[jkogel]

It looks like it's been there for a couple of years at least. They must be really into transcendental levitation!

John Kogel
www.allsafehome.ca

[Jeffrey R. Pope]

That kind of stuff is my worst nightmare. It's the kind of thing that kills people. . .

[Marcel R. Cyr]

Dang Jeff, the post would be in front of the door to make it right.

Recommend reversing the joist Hangers and posting the landing to two people maximum.

Marcel

[Richard A. Hetzel]

Hey, he read somewhere that you can cantliever two feet, so that's what he did.

The joist hangers would probably take what uplift there is as they are, if they are fully nailed. At least there are joist hangers.

[Marcel R. Cyr]

Richard, I guess he just remembers the two foot part and not the 2/3rd's back.

[Ralph Brady]

It might hold now, but who knows in another 5 - 10 years when the ends of the joist get soft. Also people seem to be getting a little heavier these days! I would not want to be one of three people along that outside guardrail.

[Jeffrey R. Pope]

Originally Posted by Richard A. Hetzel

At least there are joist hangers.

They'd be more effective if they were turned over, in this case. . .

[Richard A. Hetzel]

If they were turned over, what would take the normal downward load? I believe joist hanger manufacturers publish uplift resistance data for joist hangers installed normally and fully nailed. It can be easily checed, and the hangers pictured may or may not be adequate to resist the uplift...however, the uplift isn't any greater in the pictured cae than if the deck were much wider...it's the same number, There's just much less of the normal main span loading to counterbalance it.

[Marcel R. Cyr]

When one understands the affects of counterbalance on one of these, it is easy to relate to a cantelevered deck.
The uplift force is always reduced by the counterweight. The same force might be there, but distributed and counteracted.




Marcel

[Marcel R. Cyr]

I believe the last joist on the ends should have had one of these.




Marcel

[Jeffrey R. Pope]

Originally Posted by Richard A. Hetzel

If they were turned over, what would take the normal downward load?

I would never seriously suggest that the hangers be installed upside down. Marcel hit the mark.

[Richard A. Hetzel]

Even closer to the mark would be to adhere to the uplift resistance data published by the hanger manufacturer. Hangers in normal position do have some uplift capacity, and different types of hangers have different capacities.

Marcel's crane is handsome, but the problem with a deck is different. The crane has all of the counterbalancing load all of the time. It is entirely possible for a deck to have full live load or more on the cantilever, but nothing but dead load on the main span, and the ratio could approach 10 to 1, so the hangers had best be investigated for their ability to resist uplift under such conditions. If the capacity is insufficient, some other mans of resisting uplift should be devised. Unfortunately, skyhooks don't work in that direction. =)

[Jeffrey R. Pope]

Did you take that picture Marcel? Jumping towers was always the most dangerous part of crane operation, but this looks like a "self-raising" tower. Is that so?

Sorry for the drift. . .

[Marcel R. Cyr]

Originally Posted by Richard A. Hetzel

Even closer to the mark would be to adhere to the uplift resistance data published by the hanger manufacturer. Hangers in normal position do have some uplift capacity, and different types of hangers have different capacities.

Marcel's crane is handsome, but the problem with a deck is different. The crane has all of the counterbalancing load all of the time. It is entirely possible for a deck to have full live load or more on the cantilever, but nothing but dead load on the main span, and the ratio could approach 10 to 1, so the hangers had best be investigated for their ability to resist uplift under such conditions. If the capacity is insufficient, some other mans of resisting uplift should be devised. Unfortunately, skyhooks don't work in that direction. =)

Richard, for the sake of debate, you say that the crane has all of the counterbalancing load all of the time, yes, until the trolley picking up the load is transferred away from that balance. That is the cantilevered action.

So would be the deck to have a counter weight load all of the time, that is called the 2/3rd's balance. Backspan on cantilevered decks must be a minimum of twice the cantilevered distance.

This deck construction is wrong due to its span and the two foot maximum cantilever should not apply.

A concentrated load on the end of the cantilever has the effect of producing uplift on the joists at the first interior beam support or at the attachment to the house.

When a deck is cantilevered, the connection to the exterior wall of the house or other framing members such as a beam shall be designed and constructed to resist uplift resulting from the full live load acting on the cantilevered portion of the deck. One way of resisting these loads is with a steel twist strap at each end to prevent uplift.

Hangers do have a degree of uplift designed into them, but it is not a common practice to go around and install them upside down to compensate for the inadequate framing methods that were used to begin with.

Tech, notes from Simpson's Hangers for LU28
Minimum uplift for this hanger is 630 more than adequate for a 4'x5' deck.

1. Uplift loads have been increased 33% and 60% for earthquake or wind loading with no further increase allowed. Divide by 1.33 and 1.60 for
   normal loading such as in cantilever construction.

The deck picture above will most likely go no where, but would you put your Architectural license stamp on this set up is my question?

My reputation as a builder could not afford such high stakes.

Because of a door below the deck, standard deck building practices have been negated.

Call it as it is. Note what is observed and move on for most.
I would not spend to much time on a report for this one.
Although not right, collapse is not on the edge.
JMHO

Marcel