You may have to install double 45 degree corner posts on the
outside of the rim joist. This is tricky, no question about it. So if
you are a do it yourselfer, you might want to leave this to someone with
strong building knowledge and carpentry skills.
The reason is that the actual 45 degree corner here is inherently
weaker than a 90 degree corner. As such, it is very important that the
custom cut blocking pieces shown below are fitted properly.
Also you must use the structural metal framing connectors and the
custom cut threaded rod to get the tension right among the various
components to make this kind of deck railing corner construction detail
Click Image For Larger View
Required Hardware And Cost
There is some tricky blocking and framing going on here so take your
time and get it right. Also the hardware connections are critical.
This kind of wood deck railing design does not have a high end
finished look as the doubling up of corner posts just is not a clean
looking detail. But this will be strong for you.
Anytime you secure wood posts directly to joists you should consider
your local environment. If you live in a moist area, these posts may
rot prematurely given the large surface are contact points and exposure to the weather.
Some people however don't have the ability to build a deck rail this way or desire to install all this hardware, or notch the decking boards around each post.
If you fall into this group, there are simpler and better looking ways to install a strong long lasting deck railing post other than having to double 45 degree corner posts like this.
What you may wish to consider is to build deck railing with posts
that are connected to the deck boards by a low profile surface mount
Take for example this low profile internal wood railing post anchor shown here.
At less than twenty bucks, it can be
used in code compliant residential rail applications when installed
according to the manufacuturer's engineering guidelines.
A Simple And Cost Effective Option
This is a potential solution for building new wood deck railings,
replacing rotted railing posts, or as support posts for pergolas,
gazebos, decks, etc.
Then watch this video of a surface mount wood post anchor that has been tested for use with wood deck railings and costs less than $20 with all the hardware you will ever need and it covers all the possible situations described above.
So there you have it.
A detailed explanation of installing double 45 degree corner posts with traditional joist framing and hardware and an alternative solution for great looking railing. You decide which is right for your specific project.