I have an existing third floor deck (10'x40'). It is supported by a
6"x12" beam resting on 18' tall 8"x8" posts.
My question: I want to install a second floor deck, underneath the
existing deck, by tying into the existing posts. Which is the best
way? One contractor recommended notching into the existing posts and
inserting 4x12 beams. This seems like more work and also means
cutting halfway into the post and weakening it. Another contractor
said to tie into the post with custom made hardware or maybe a Simpson
connector. This method seems simpler, but will the ties support the
weight of a deck and people?
I haven't seen either method in any of the how-to books. They always
show the beam resting on top of the post.
Simpson makes several connectors that might do the job. You could also
add a bearing block bolted to the post that the new beam will rest on. If
you use this method be sure to add some straps or other ties to keep the
beam on the bearing block.
Bob Morrison, PE, SE
R L Morrison Engineering Co
Easy to answer. The best way is the one that will be approved by the
building inspector. I cannot imagine the problems if you were to notch the
post and the building inspector refused to approve the deck.
I agree that notching the post may not be best, at least cutting them half
way. There is a lot of different deck hardware at www.mcfeeleys.com They
may have what you need.
You'll will probably need a building permit for this project. Check with
your local building inspection department. To get the permit, you will need
detailed drawings with structural calculations. Existing posts might need
reinforcing, depending on the additional load of the new deck. You may need
additional bracing members for the posts, since they are very tall. In
other words, you should have it designed by a structural engineer. You are
dealing with heavy loads and tall posts and don't want to see it collapse
the next time you have a rowdy party.
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