Today we’re talking newel posts and how they relate to Newtons, a measurement of force, and not Newton, Hercules’s centaur buddy.
Let your mind wander to thinking of English physicists.
Essentially, one Newton is the force needed to accelerate one kilogram of mass at the rate of one metre per second, squared. The KiloNewton is a unit of force where one KiloNewton is equal to one thousand Newtons.
Because the building code tosses around the term kN (KiloNewtons) like Santa’s elves do candy at a Christmas parade, familiarizing yourself with Newtons and KiloNewtons will get you well on your way to understanding how to fortify your deck in order to meet those resistance loads insisted upon us by the building code.
Conversely, if you happened to have skipped the six years required to secure a master’s degree in engineering, and perhaps lack the educational background to fully comprehend KiloNewtons, and the various other mechanical bibble-babble found in the building code, let’s put the element of KiloNewtons into layman’s terms.
Essentially, one Kilonewton equals about 225 pounds of pushing force. The building code demands your newel posts be able to withstand a vertical load of 1.5 KiloNewtons, about 338 pounds of force, which is akin to either being put in a headlock by your average professional wrestler, or surviving the tugging force of at least three members of the McCulloch dance troupe.
So, considering the push/pull power of Highland dancers – they may be slight, but they’re mighty – deck builders should give serious consideration to the proper installation of their newels. Plus, building inspectors may or may not jump up and down on your deck to test its worthiness, but they always shake the post, and on a combined diet of black coffee and the day’s roadkill, along with early morning viewings of Die Hard I and II, these people are motivated to induce movement.
No matter how secure you fasten a newel post, when vertical (push from the side) pressure is applied to the top of a post, essentially at its weakest point, it’s going to move. The degree to which your newel moves, and how quickly it rebounds back to its perpendicular state, will determine its worthiness as a post, and the resulting security level of your railing system.
All railing systems have engineered drawings which outline how exactly a newel post in their system is to be installed.
Railing systems without engineered drawings are not acceptable, will not pass code, and will have to be dismantled if ever installed. So, avoid bargain brand type rails, yard-sale junk, or bidding on some beautifully ornate rail system at an auction.
What passed code in the 1930s won’t meet today’s standards.
So, unless you plan on using such a rail to decorate the area surrounding your lawn or garden area, or you’ve secured the engineering paperwork with a 2019 re-evaluation, keep it off your deck.
The key to a solid newel post is the blocking, or basically the mass of wood product that will accept the necessary lag screws or bolts that secure the post base. PVC (vinyl) and aluminum railing systems generally have newel posts that come with their own type of steel sleeve or base, which makes the surface mounting of these posts relatively straight forward.
Now, however good or engineered a post system is, failure is certain should you simply fasten these posts into the 5/4-inch decking. Effective blocking will mean placing 2×6 (for bolts) or 2×8 lumber (for accepting six-inch lag screws) underneath your decking planks.
Be sure to laminate the blocking with the help of a PL Premium glue, and secure the blocking into the joist system.
For composite and certain PVC systems, a 4×4 treated post will form the bulk of the post, with a decorative PVC or composite sleeve sliding overtop. In cases such as these, the 4×4 post will need to be buried into the joist system, and not surface mounted. Again, 2×8 blocking will be necessary in order to firmly secure the 4×4 on all four sides.