Background: I have a 6yr old new construction home. A small deck (roughly 9x9 if you exclude the stair cut out) was built just to come out from the kitchen. The house has a garden view basement, because the house is built on a slope.

Objective: I'd like to extend the width of this deck about 16-17ft, and basically keep the old deck, minus the railing at the side I will be extending.

Currently the deck is connected to the house by a ledger board, and then the front uses slotted 6x6 posts to support the rim joist.

What would be the best way to extend the rim joist into the new deck? I haven't built a deck before, but I would like to tackle the job myself. I do plan on submitting a permit and plans next week to my city's building department.

I was tossing around some ideas: Should I put another 6x6 as close as possible and have the extending rim joist cantilever a foot or so to the old deck? Should I try and cut back the old rim joist to where I can seat the two (new and old) together on the original 6x6 post and extending from there? Or can I just somehow attach the extending rim joist to the end of the original deck (the band joist)?

Here is a picture of the original deck when it was first built to get an idea of what I'm working with.

Picture of current deck

  • do you want to extend away from the house or parallel to the house?
    – Jasen
    Jun 25, 2022 at 23:13
  • Parallel. I want to extend off that right side (right side when coming out from the sliding glass door) in the picture.
    – eaglei22
    Jun 25, 2022 at 23:24
  • A rough sketch - a birds eye view looking down - would be useful. Sometimes it's not clear what is meant by "width", or "length".
    – SteveSh
    Jun 25, 2022 at 23:24

1 Answer 1


It should be acceptable to cut back the existing rim joist and ledger to allow supporting one corner of the extension on the same post. assuming the post and footing are sufficient for the added load.

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    chicago.gov/content/dam/city/depts/bldgs/general/EZPERMIT/… - page 80 shows two ledgers abutting, with two bolts each, sitting above a bracket bolted to a 6" column. +1. You could use a bracket and not have to cut anything, but notched is better. assuming the post and footing are sufficient (+2) if it's the same size as the one in the middle, it's prob fine.
    – Mazura
    Jun 26, 2022 at 1:38
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    @eaglei22 - I was thinking you could use a bracket attacked to the face of the 6x6 we're looking at (but it's never that way in any of the pictures; you wouldn't be able to put bolts into the new edge beam). However I see very few bolts anywhere. :\ the only place screws belong is in the decking. The only place notches ever belong is this instance. Use a Fein saw to cut the 2 edge beams down the middle of the 6x6. DO NOT over cut into the 6x6. Put through bolts or at least giant lag screws x2 (not 1) into every railing post, and beam-to-post connection. Options yes; none that meet my code tho
    – Mazura
    Jun 26, 2022 at 19:07
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    @eaglei22 - bracket (but you shouldn't use it; do notches like they did, to match). - The rim joist will just become a normal joist, now somewhere in the middle (it doesn't have anything to rest on; should be bolts, not screws). - The upper edge beam rests on a x2 edge beam, where the inner one has the joists resting on it with screws into the face of the x1 edge beam. That lets you get away w/o metal hangers. - The only thing keeping it from being able to lift is those 6 (x2) screws in the rim joists. Which, again, should be bolts. Chk top link ^
    – Mazura
    Jun 28, 2022 at 1:57
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    @eaglei22 - Depends on if you have to pass inspection. If you didn't do all that, you've got a joist in the middle of the deck w/o a hanger (permissible only on rim joists). - I'd be fine with galvanized angle brackets with SS lag screws on both sides. lowes.com/pd/…
    – Mazura
    Jun 28, 2022 at 3:32
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    @eaglei22 - Okay then, the only thing holding it down is gravity ;). You can either ask if brackets for the old rim joist are okay instead of a joist hanger. Or just do it (lot of work). Or just try to get away with it. I'd call and ask.
    – Mazura
    Jun 28, 2022 at 3:38

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