I have a need to mount three newel posts to a 3/4" subfloor. I don’t have access from below (finished basement).
The current newel posts were mounted using a flange plate that was bolted to the bottom of the newel, then bolted to the subfloor. This works fine with carpet, but I will be putting hardwood down.
What’s the best way to anchor the newels in this situation? Home Despot has L-brackets, but it just doesn’t seem to me that they would be all that strong. The newel post is a box newel that is 5"x5" at the bottom, so fairly substantial.
Do they have a bolt system that has heavy-duty fingers that pop-out after you put it through the subfloor that can grasp and hold a bolt in, that could be used to screw a nut down on the bolt from within the newel post?
Or should I do a plate like they did before and let the hardwood floor installers work with it?
Box newels are the best! Square the end perfectly, half inch bolt, big washers, nut and a long extension to tighten it up with. Solid. If there is proper backing (like a chunk of LVL or 2x8 blocks you use a carriage bolt.
You really need some sort of access from below with a bolt, if you are not willing to do a ceiling patch in the basement (its a BASEMENT after all), then you can do a floor patch, but it has to be solid.
There next best is a system with a heavy plate with welded post. The plate bolts to the floor and the newel post fits over the steel post with with a sleeve or precisely bored hole. After that is just a heavy oversized plate that screws to the newel then to the floor.
There are other systems with brackets and little double threaded bolts but they tend to be flimsy.
3/4" sub floor by itself is pretty flimsy for this purpose. In new construction heavier backing is usually installed at the back framing stage so the balustrade contractor has something strong to sink a carriage bolt into. If there is no backing I would open up the ceiling below. Every time.
On This Old House I’ve seen them attach newel posts using what I believe are called hanger bolts. Big wood screw on one end and machine threads on the other. They bored a hole into the side of the post and another from the bottom to pass the hanger bolt. After using the access hole to tighten the washer and nut onto the hanger bolt they plugged the access hole with a matching wood plug.
Here’s a video on method. Its using the locking plate. It means the Newell , and rail , can be removed.
Maybe this is wanted for a child safey rail, or to assist when trying to move furniture up the stairs ??
If you’re working on newel posts perhaps there’s flooring work as well. If so, maybe an access could be made through the subfloor to install reinforcing members and then reinstalling the subfloor.
I don’t trust 3/4" wood or wood-like substance for a functional newel post.
The only one I ever owned was secured to a 2x10 joist - and it had a precise box built around it for additional security.
Main point:
THIS IS REAL CARPENTRY - STAY AWAY FROM BIG BOXES!!
This is especially true with steel products - the difference between the HD version of a post bracket and the ones used by the professional is a Yugo vs a real car.
Don’t mess with toys - which is what the big boxes sell (but they’re cheap! Yes, they are, aren’t they).
p.s. - green lumber is wood that has not been dried - they actually are cutting green wood to finish dimensions (and shaving 1/16" from even that). Green lumber will dry - and, as it does, it will warp, twist, and split.
Use big box lumber* for a kid’s tree house or other temporary structures.
they do sell dried 2x4’s and smaller - look for “KD” (kiln dried). Most redwood is not dried.
