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-   -   Building roof over a deck (http://www.diychatroom.com/f19/building-roof-over-deck-121739/)

accan3 10-29-2011 05:07 PM

Building roof over a deck
 
I have an existing deck that is 12'w x 42' l. The deck has the cross beam under the floor joists at 10', then the 2' overhang.(to make up the 12') So my question is how could I build the post supports for the roof so that the posts are not 2' into the deck(in order to be on the beam underneath?) but rather out on the cantilever in line with the railings. The deck is 9' off the ground and do NOT want to add attitional posts to support the cantilevers.

Just to avoid those asking if posts are adeqate to support the roof, The posts are to engineer's specs to handle a roof. Original engineered design was for a 10x42 deck with a roof. Unfortunately the 2 foot cantilevers is now causing me a design issue.

Thanks for your suggestions

rossfingal 10-29-2011 05:17 PM

Pictures would help.
Size of posts and joists - size of beams?
Spacing of joists?

RF

accan3 10-29-2011 05:22 PM

Sorry dark outside right now can't take pic's. The joists are 2x10 (16 on center), beam is 3 2x10's and the posts are 6x6's.
Thanks

rossfingal 10-29-2011 05:36 PM

You should probably consult your local "Code Enforcement Entity" -
Building Dept.
Tell them what you've got - maybe have them look at it.
Tell them what you want to do.

rossfingal

Daniel Holzman 10-29-2011 05:46 PM

If I understand you correctly, the original design called for posts near the end of the joists (approximately 12 feet from the house). The posts were designed to carry through the deck in line and extended (8 feet?) above the deck to support the roof. Apparently the deck was built slightly differently than the plans, where you now have a two foot cantilever, and you want to install the roof support posts approximately in the same location as originally.

If this is correct, you will now be imposing a point load on the cantilever side of whichever joist you attach to. This type of load certainly was not anticipated in the original design. Not to say that it won't work, but it needs to be engineered. If your building inspector is unwilling to sign off on this modification, as I suspect is likely to happen, you are probably going to have to go back to the original designer to get your deck redesigned.

accan3 10-29-2011 05:59 PM

The deck was designed to be 10' wide and the beam was at 10' as well, lumber yard only had 12' joists so I decided to keep the extra 2'. In any case I do agree with you that having the roof posts out on the cantilever just seems like a bad idea but wanted to get some thoughts/opinions before I moved forward with getting an engineer involved.

Thanks

Joe Carola 10-29-2011 07:29 PM

Quote:

Originally Posted by accan3
The deck was designed to be 10' wide and the beam was at 10' as well, lumber yard only had 12' joists so I decided to keep the extra 2'. In any case I do agree with you that having the roof posts out on the cantilever just seems like a bad idea but wanted to get some thoughts/opinions before I moved forward with getting an engineer involved.

Thanks

The simple answer is no because it wasn't built at 10'. Posts cannot be out on the cantilever. Posts were designed to be above the bottom posts at 10'.

woodworkbykirk 10-29-2011 09:03 PM

the only way to effectively have the posts at the edge of the deck is to a) install another beam at the edge of the deck which is sitting on piers or cut back the deck eliminating the cantilever

robertcdf 10-29-2011 10:22 PM

I can't say much that hasn't already been said just another vote of no.
Last year we tore down a double decker that had been built similar, the lower deck was 12' out from the house with a beam and posts at 10' out, the upper deck was 12' out with a beam and posts at 12'... The weight of the upper deck was pushing the rim right off the lower deck horribly. We had to support the upper deck with a temp beam to even tear it down.

accan3 10-30-2011 07:45 PM

Thanks to everyone who replied. I knew it wasn't likely feasible, you saved me from having my engineer charge me to tell me the same thing.

Joe Carola 10-30-2011 11:27 PM

Quote:

Originally Posted by accan3 (Post 760424)
Thanks to everyone who replied. I knew it wasn't likely feasible, you saved me from having my engineer charge me to tell me the same thing.

You can ask an engineer if you can use 3-1/2' or 5.5" x 9-1/2" high x 12' length treated Glulams, or whatever size your joists are. You can have them set above each post underneath your 2x10 beam. On the outside at the 12' point(cantilever) you can have new posts out there to support the roof. I've framed houses this way in certain situations, but all designed by an Architect.

This will transfer the load on top of the Glulam outside which can support the posts and roof and itself with the 2' overhang. Again, this is an option that I have done framing. You have to see if it can be done in your area.

http://www.rosboro.com/index.php?act...oducts.treated

Marvel 11-02-2011 12:51 PM

Have to agree with Joe. Adding knee braces on a 45 back to the posts will help. Also suggest you install upside down beam saddles ( alike to joist hangers) at the house end of the new beams. The cantilever will create uplift at the house end.

accan3 11-03-2011 07:34 PM

I'm not sure I understand your suggestions? are you just saying to add a new beam and new posts under the 12' point of the floor joists instead of the current 10' point + (2 foot cantilever) ?

Marvel 11-04-2011 08:56 AM

Not sure to whom your question is directed.

orange 11-04-2011 11:15 PM

Quote:

Originally Posted by Marvel (Post 763632)
Not sure to whom your question is directed.

I think he is asking Joe to describe the configuration he mentioned.
Perhaps a drawing would clarify this

Quote:

You can have them set above each post underneath your 2x10 beam. On the outside at the 12' point(cantilever) you can have new posts out there to support the roof.


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