One of the first things to decide is which way you plan to build your guardrail posts.
You can mount them to outside of the rim joist. Or you can secure them inside the perimeter joist and along or between the main floor joists. Finally, you may wish to go for a surface mounted post.
These are all important questions to understand and answer before you go further along with your building plans.
You might wish to read more about this topic in this article and then come back here.
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