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I have a small landing and set of stairs that need to be built in a fairly small space up to our garage pad.

I have a limited area to work with so the landing serves as the first step down in order to keep the stringer from getting too long. Unfortunately this means I cannot attach the stringer to the joist as it's lower. To resolve this, I'm thinking I'll place a second 2x8 below the joist.

How should I go about fastening/attaching this "joist extension" to the main joist above it?

I was thinking of using a 2x10 or 2x12 backer, and fastening with structural screws, but I am open to other ideas.

BONUS QUESTION: Should I attach the stringer closest to the concrete wall just like a ledger (and maybe back it off 1/8th with some galvanized washers?) Or is it better to NOT attach it to the wall and leave it free like the other stringers?

Note: If you're wondering WHY 5 stringers or 2 "extra" interior joists, they are needed because the decking is composite and recommended by the manufacturer.

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3 Answers 3

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I've used two strategies here.

  • For interior cases it's common to use doubled 3/4" plywood attached to the the rim joist with 2-1/2" screws. Here you could use pressure-treated plywood attached to the back of the rim so it's less conspicuous. Extend the stringer as needed to reach.
  • Run the stringer to the second joist, passing underneath the rim. You may need to revise your joist layout to make this work.

I would not fasten the side stringer to the concrete. If you suspend your stairs properly this doesn't accomplish anything and damages your concrete.

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  • This is very interesting - are you able to shed any light onto why I might opt for plywoood over two-by timber? Also wondering if construction adhesive rated for wet/outdoor is appropriate in addition to fasteners? Not sure what code has to say (if anything) about the use of adhesives. Thanks you!
    – Ray
    Commented Apr 22, 2022 at 16:34
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    Adhesives applied on-site are never considered structural, to my knowledge. Plywood has strength on both axes, whereas solid lumber has strength in only one.
    – isherwood
    Commented Apr 22, 2022 at 16:37
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for the added joist connect one end to the post and support the other end with a 2x4 run vertically connected with structural screws. (or use 2x8 if you have plenty of that, but 2x4 will be fat enough) cut the top end of the 2x4 to slope away the joists so that it sheds water. 10 degrees of slope is plenty.

Seeing as the left stringer is not supported by the foundation wall neither should the right stringer be connected there. support them all equally.

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  • Jasen, when you say to cut the top end of the 2x4, do you mean cut the top so it has a slight mitre? Thanks.
    – Ray
    Commented Apr 22, 2022 at 16:56
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A landing is required if the door swings outward, except for screen doors. The landing is to be the width of the door and 36” in the direction of travel. (See ICC R311.4.3.)

The maximum rise of steps is 8”. The maximum difference between risers is 3/8” from smallest to largest. (See ICC R311.5.3.1)

The minimum tread depth is 9”. The greatest difference from smallest to largest is 3/8”. (See ICC R311.5.3.2)

A handrail is required if there are 4 or more risers. The handrail is to be installed a minimum of 34” and not to exceed 38” (See ICC R311.5.6)

Handrails are required on one side only. (See ICC 1009.15) It’s customary to have it on the right side descending, but not mandatory.

Handrails are not required if there are 3 risers or less. (See ICC 1009.15.4)

Handrails are required to be a uniform height between 34” and 38” above the nosing. (See ICC 1012.2)

Make sure you have a minimum of 1 1/2” clearance between the handrail and wall. (See ICC 1012.7)

To answer you question, you’ll need to move the stair stringers up so we every tread is at a uniform height. You can fasten the stringers to the porch with Simpson U26, or something similar. Just cut a kerf in the stringers at the appropriate height.

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    You may want to move the actual answer to the top and put in a bold or header with the reason why following. I was wondering how this answered the question until I got all the way to the end.
    – FreeMan
    Commented Apr 22, 2022 at 11:23
  • @Ray A) based on your drawing (without any measurements), the top step to platform looks taller than the rest. B) Answers that are supported by "copy-paste nonsense" code are considered to be much stronger and valid than "some guy on the internet said". C) You took the time to make a note of why you have so many stringers, so not having a note about the missing handrail indicates to the cautious reader that you might not have planned to put one on. We do try to answer in the safest way possible because not everyone knows what the proper way to do things is.
    – FreeMan
    Commented Apr 22, 2022 at 16:01
  • I hear you - apologies for being overly direct to Lee. Some other stack exchanges have a strong prevalence of well-meaning people copying and pasting - and I believe its important for the community to not just give snippets from the code, but also provide context, wisdom, and to seek clarification - otherwise whats the point. But I do take your feedback seriously and I'll delete my comment and provide something more constructive. Thank you.
    – Ray
    Commented Apr 22, 2022 at 16:38
  • @Lee, thanks. Unfortunately it doesn't answer my main questions, but happy to explain why: I opted to omit certain details from the plan, including the railings and a bunch of the critical dimensions as my main question is around how to safely and correctly fasten the "lower" joist aka "joist extension" to the upper one. I sized the stringer using this (I understand its commonly accepted) method in order to shorten it and keep it from running out into our garden beds. rest assured though, I'm following the IBC (building codes) for this. You should see the old stairs!!
    – Ray
    Commented Apr 22, 2022 at 16:45
  • @FreeMan Please re-read the last paragraph. I gave the correct hanger to use and how to modify your stringers to fit into the hanger and gave you a “tip” on how to make the steps all equal. Often people are concentrating so hard on one issue (like fastening stringers to deck) that they are not seeing the big picture (uniformity of risers, handrail, etc.) BTW, your deck is now required to be fastened to the house (if not freestanding) with 2 connectors…1 at each end of the deck, but you don’t want to hear about that.
    – Lee Sam
    Commented Apr 22, 2022 at 17:09

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