Decks, Patios, Porches and Docks - second story cantilevered balcony support questions

Hello all,

Buddy of mine just had an addition put on. Builder put on a 6' wide by 4' deep cantilevered balcony on second story. Buddy now wants the balcony 6' deep and the width of the house which I'm guessing is somewhere around 25'. Questions...

Is this even possible from a safety standpoint?

What does code say?

Buddy will be pulling the permits and doing everything legit, but first wants to get an idea of what the job will involve. He doesn't want the supports as he has a walkout basement and its obviously pretty high up to the second story balcony which sits directly over the walkout basement.

any help would be appreciated...

Thanks,
ron

Are you talking about a cantilevered deck with no posts at all or a deck with a ledger at the house and posts out further?

If it is a true cantilever, it will be a very big project the the possiblity of leakage/rot back into the house. The catilever (if legal) will involve removing the existing 4' cantilever (unless it was double over-built) and sistering new 2xs (if you are lucky) to your existing interior joists. You can expect some problems with deflections - heavy furniture and loads inside can tip the cantiver up causing water to drain back toward the house. Movement of the deck can give you vibrations inside.

Cantilevers look great but there are a problems. Going from 4' to 6', will be surprised how much light a second floor deck will cut off - good or bad depending on the exposure direction.

Dick

He wants a true cantilever that extends out 6' from the house with no support posts.

Seems like a big project to me. It just seems that there is so much to consider. One thing I just thought of is the load that will be added to the existing wall(the wall supporting the lumber of the cantilever). I'm not sure if that wall is 2x6 or 2x4 but either way thats a lot of weight added.

ron

In our county you can have a maximum 2 ft cantilever - if you want more you have to have engineered drawings and it's still subject to approval. I have heard issues like those described by the others, but instead of heavy furniture pushing the deck "up", the deck was so heavy it sagged and caused a big bump at the end of the sistered joists inside the house. A huge section of the floor had to be cut away to make the repair.

FWIW we have a small 5 ft cantilevered deck on our house and have never had any issues. It was an original installation when the house was built about 18 years ago. However I think the deck joists are actually the floor joists (no sistering) and solid log walls prevent shifting. On the other hand, we don't use it much - it wiggles a little more than I'd like too.

Logcabincook brings up my primary objection to cantilevers. They are cute, but the havoc they can create if not properly done costs a bundle to correct. The last one I had experience with, the builder put out an 8' cantilever with only 6' sistered in the main floor joists, and then only nailed at that point rather than bolted. Tile in kitchen erupted. I was so glad the owner was just asking for advice rather than asking me to correct it. I won't touch them.

This project may just not happen.

Off the top of my head I was thinking about sistering TWO 18' 2xwhatever matches the floor joists, one on each side of the floor joist. That would give him 6' out from the house and 12' inside. We would then have to take a look at beefing up the support wall maybe adding studs or redoing the wall to make the studs every 12". Remember this is would be on a newly built addition so everything is still accessible.

These are just ideas tho. Would never attempt anything like this without having the go ahead from the city and the proper engineering.

Maybe support posts are the way to go....

ron

If your buddy is smart, the project WON'T happen!!

As has already been posted, it would have to be engineered. That's one expense.

ALL of the interior floors would have to be torn out to get the proper size beams tied in properly to support a 6' cantilever. The expense of that will dwarf the engineereing costs.

When all is said and done, those beams hanging out there in the weather are an extension of the floor joists. Once they start to rot (and wood, exposed to weather WILL ROT!!), he'll be tearing everything out, including the interior floors again. If he's lucky, that'll be 20 years down the road!!

(And now you are beginning to understand why I HATE cantilevered decks and simply WILL NOT build them!)