INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Jobs

Balcony for upper level

Balcony for upper level

(OP)
I am designing an addition for a client and he would like a balcony on the upper level. It is a 24' wide addition so the floor joists will be spanning 12' from a wall in the middle of the addition to the exterior wall. He would like to go 8' out but the cantilever distance would be greater than half of the interior joist span.

How do you analyze the joists if he were to install a diagonal member from the exterior wall to the middle of the 8' cantilever? Similar to the diagonal piece in the attached image.

RE: Balcony for upper level

You'd treat it as a 4 ft cantilever with a 4 ft span and then a 12ft span. The problem will be getting the exterior wall to calc out for the moment you're now putting into it with the diagonal support.

RE: Balcony for upper level

Why don't you sister other joists off the 12 ft. interior joists and extend them out?

Check out Eng-Tips Forum's Policies here:
FAQ731-376: Eng-Tips.com Forum Policies

RE: Balcony for upper level

Still can't get a reasonable joist to work for an 8ft cantilever with only a 12ft backspan.

RE: Balcony for upper level

(OP)
JAE, are you saying basically installing a double joist but one ends on the exterior wall and one cantilevers out 8'?

RE: Balcony for upper level

If you must use 2x material (vs. engineered composite lumber) then perhaps an 8 ft. cantilever using a 16 ft. board lapping your interior 12 ft. joist.
You would have to work out the nailing between the interior and exterior to ensure an adequate load path.
You would also want to check, very carefully, the deflections. An 8 ft. cantilever seems quite long to me.

Or you could use double joists on the interior and double sistered cantilevered joists.

For a balcony cantilever, exposed to weathering, moisture fluctuations, and inherently non-redundant, I'd also consider doubling my safety factors.

Remember this collapse in Berkeley a little while ago? : http://www.vosizneias.com/206607/2015/06/17/berkel...

Check out Eng-Tips Forum's Policies here:
FAQ731-376: Eng-Tips.com Forum Policies

RE: Balcony for upper level

(OP)
JAE, so double 2x joists (12' long) on the inside and then double 2x joists (20' long) with 12' sistered onto interior joists?

I was thinking of using LVL's but can they be left exposed?

RE: Balcony for upper level

Quote (jimtheengineer10)

I was thinking of using LVL's but can they be left exposed?
No. There is a parallam plus product approved for exterior use but I haven't yet come across an exterior grade LVL product.

RE: Balcony for upper level

or try AYC all-heart glulam,
decay resistant,
20F-V13 AC/AC Fb=2000 E=1.5 (check me)
can normally get fabricated in any depth you want

RE: Balcony for upper level


As the image that JAE shows, I would never advocate cantilevering interior floor joists for an exterior balcony. The detailing of, and actual construction of, the building envelope requires careful attention and simply invites future problems. Far too many penetrations through the envelope and it will be prone to issues a la Berkeley.

The lifespan of an exterior wood-framed deck is far shorter than the structure, even using the best P/T products. How will the deck be repaired in the future when it is overtaken by rot?

I would rather see 2 or 3 steel members penetrate the building envelope and run the deck joists parallel with the exterior wall. This way the future repair/replacement of the exterior deck will be far easier and (hopefully) will not involve any modification of the building envelope.

JMHO

Ralph
Structures Consulting
Northeast USA

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close