I have and existing deck about ten feet off the ground. The joists are all doubled up 2×6 S. Pine 11' 7" in length. There is a double 2 x 10 beam running across the middle. I need to remove this beam. I need to install some corrugated roofing to create a dry space but I can't do it with the beam in the way. I have seen several tables that say 2×6 can be used but only for a 9 foot span. My joists are all double runs of 2×6's. Can I get rid of the beam?
Thanks,
Mike
Span 11 feet 7 inches with doubled 2×6 deck joists
deck
Related Solutions
This is quickly going to become too complicated to tell you for sure if your deck will be able to support a structure like a pergola, but if it is even half the weight of your typical hot tub then your deck will very likely not support it.
To accurately determine this you need to figure out the additional #'s/sq ft of load that a structure as large as a pergola will place on top of the deck. Doing this is simple with something like a spa where you have a clear square footage area and a relatively even weight distribution when filled with water and people. This is not so easy to determine with a structure where certain points of the structure are going to carry the weight of the structure differently. The weight is not as evenly disbursed.
Right off the bat there I would advise you to consult an engineer with your structure plans to determine if this is feasible and safe. This is completely disregarding the fact that your deck is only as strong as its weakest point. If your house is brick and your ledger board is attached with carriage bolts then even if the joists were on 12" centers then you are still likely putting entirely too much stress on the ledger board. You also could have a lot of problems if any part of your structure is going to sit over that 2' overhang.
In the end, an experienced engineer will probably be able to confirm pretty easily if this will be feasible or not.
How to interpret the American Wood Council’s Design for Code Acceptance table of cantilevered joists
Directly from the document that you linked the following figure shows that the Lj and Lj/4 dimensions are additive.
Related Topic
- 2×6 deck joists: salvageable or need replacing
- Frame over an existing deck with a new deck to raise the level
- Will 2×10 13’6″ span support outdoor bbq
- How to straighten a twisted 2×6 deck board
- Is using a single hanger plus a framing angle on a double member sufficient
- How to hang joists that are supposed to be doubled, but that will sit over the joining of two boards
Best Answer
Doubled 2x6 joists are probably strong enough, but they're not going to be rigid enough to prevent significant bounce. That's why joists spanning 12 feet are usually 2x10 or 2x12. You need to upgrade your joists and possibly the single remaining beam to eliminate the intermediate beam.
Alternatively, consider cutting the intermediate beam into the joists to be flush on top, and add joist hangers. This would raise it by 5-1/2".