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    George W's Avatar
    George W Posts: 1, Reputation: 1
    New Member

    May 29, 2008, 10:21 AM
    Adding A Cantilever Extension To An Existing Deck
    I think I made a mistake when I tried to post this the first time so I apologize in advance for any duplicate.

    I would like to add a 2' cantilevered extension to an existing deck which is 9 1/2' wide, 45' long and 4' ~ 10' of the ground.

    The builder attached a 2" x 10" ledger to the cottage, placed 4" x 4" posts 9 1/2' from the ledger on 8' centres, nailed a 2" x 8" rim joist to the posts level with the ledger and ran 2" x 8" joists on 2' centres between the rim joist and the ledger. It was inspected and approved (which surprizes me) and has been there for 18 years. I have since bolted a 2" x 10" beams to each side of the post to support the joists.

    My plan is to remove a 24' section of the rim joist (the joists are now sitting on a 2 x 2" x 10" beam), attach a new longer joist to each existing joist then reattach the rim joist. I have a couple of questions and would appreciate any input:

    * Does this plan make sense?
    * If I extend the new joists by 2' do I need to install 11 1/2' joists going back to the ledger or would new 6' joists be just as good?
    * How many screws per foot do you think are required to secure the new joist to the old joist?

    Thanks in advance for your comments.
    wildandblue's Avatar
    wildandblue Posts: 663, Reputation: 57
    Senior Member

    May 30, 2008, 11:44 AM
    The 4x4 posts are adequate but I would have gone with 4x6 or 6x6 posts on such a tall two story structure to give a visually more massive and solid look instead of tall and skinny. Is there a roof of some kind over this or is everything completely out in the weather? Is the space underneath the 10 foot high deck considered part of your living area? Is this pressure treated wood? I'm thinking those existing joists are 18 years old and could need replacement fairly soon. Also that they still have some useful life left in them. I would hedge my bet and install new joists full length toward the center of the structure where they carry the most weight and the shorter lookout joists toward the ends. Spike them together using at least a 10p nail every foot driving them in from both sides of the joist so they don't pull out. Or use a couple of carriage bolts with big washers and nuts. I like to use a 16p galvanized spiral deck nail and bend the ends over after driving them completely through.

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