Attach Newel Post To Floor Joist
The 2x s would act like a giant toggle bolt.
Attach newel post to floor joist. This will let the stair skirt board die into it the box newel will extend to the floor and the nosings will butt into either face of the bow newel. If there happens to be a joist where the newel will install you might be able to use lj 3005 or lj 3006 mounting plates. In new construction be sure floor joists are installed at the correct spacing. Or you can make your own mounting plates if the newel is larger than lj s are made for.
Smith 3008 10 to secure the newel. You will need a box newel with a long enough bottom section to notch over the joists and attach it to the sides of the joist through the face of the box newel. I used to use plastic shims to level my post but since i started using the 4 js system no more shims and i. It was kind of tricky to get the post perfectly flush with the floor while still being perfectly lined up because of a nearby post i had to tighten it by driving it perpendicular to the rail sure was stiff though but could be my memory chips are failing.
Another way to install newel posts is the angle bracket newel post fastener installation method. If i were attaching that newel post i would still try to figure out a way to gain access to a floor joist for attaching the replacement. The 4 js is the mount i use also very easy to level the post with the 4 js system i fasten the j brackets a little shy of being flush with the bottom of the newel post and then snug the screws down into the floor and check for level then tighten the direction i need to move the post. On center which won t properly support some composite decking products when installed on an angle.
You just need 4 six inch long rail bolts. Then attach one angle bracket to each side taking care that the angle bracket does not extend below the bottom of the post. Agree that nothing beats going to the joists but i have used a newel plate once needs good framing flooring and it blew me away. Then use a suretite newel bolt l j.
Anchoring is superb this way. Bolting a newel post down to the top of the floor is easy. In existing decks adding more floor joists is the only remedy.