Fastening Newel Posts to Floors

Without tearing things apart, how do you attach a newel post to a floor framed with floor trusses and subflooring, with laminate flooring installed over that? July 3, 2006

Question
I have two box newel posts to install on a straight run on the main floor. The ceiling below is all finished.The floor that the railing goes on is a laminate wood floor. The floor framing consists of clear span floor trusses with 1-1/2 inch top cord - not enough to fasten anything to. Short of tearing up the floor or ceiling below, does anyone have any ideas on fastening these and making them solid?

Forum Responses
(Cabinet and Millwork Installation Forum)
From contributor A:
I guess if the box newels are hollow, I would take a solid block of wood that fits tightly inside the box at least 4 inches up and screw the heck out of it to whatever I could find under the floor. Then fasten the box newel to the block - assuming you could screw that block to the top cords of the truss. If you only hit subfloor you may get too much flex in the subfloor. The other idea that comes to mind is to use a giant Molly bolt - those butterfly bolts that you typically stick thru the drywall and the wings pop open - usually used for hanging lightweight things in drywall but the same principle. If you could find a big enough one you would have to fill in the bottom of the posts and drill a brass insert to thread the Molly bolt into. Then drill a hole in the floor to insert the Molly and turn the post until it's snug enough. But you will still get flex from the subfloor. If this is a railing it supposes that it is near an opening in the floor. Usually the joists are doubled around openings to reduce sag and flex. If that's the case you may be able to hit two joists (trusses) and then you'll be solid. Do you have any old prints from the house? If it's laminate and you're near the edge you might better just take up a few strips of the laminate. Just whose idea was it to lay the laminate before figuring out the newel posts?

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From contributor B:
Since you will be installing over a laminate (floating) floor, you will have to cut the flooring out anyway. You could then cut a hole in the underlayment, slightly smaller than the size of the newel, and insert a couple of 2x's glued and screwed together, about a foot or so long, and fasten to the underside of the underlayment with construction adhesive and a couple of angled screws. Then use a Suretite newel bolt (L.J. Smith #3008-10) to secure the newel. The 2x's would act like a giant toggle bolt. 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. Or you can make your own mounting plates if the newel is larger than LJ's are made for.

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From contributor C:
We use threaded rods in this situation. The rod is secured through a centre hole in a steel plate at the floor. The plate is lag screwed into the floor (alternatively, you can fashion an angle iron to sit on top of the stringer depending on the particular situation.) The rod runs up through the hollow post and through a hole in the cap. It gets tightened down from there. Your newel design needs a cap that will hide the bolt and nuts at the top. Usually boxed newels have some sort of stepped cap detail (more than one level) so this is often a good way to go.