Length Of Deck Screws
I want to attach flooring boards (2 X 6)
to deck frame (also 2 X 6). What length deck screws should I use?
Should I use fine or coarse threaded screws?
One more question -- is it necessary to drill a hole all the way thru the
flooring board? Does that make the screw hold the floor to the frame
thread screws are used for attaching to wood. Fine thread screws are
primarily used for attaching things to metal studs.
The general rule of thumb I've heard is ONE INCH of penetration into the
framing material, though some builders prefer 1¼" or 1½" of penetration.
Since your 2x6 decking is 1-1/2" thick, you can
use 2-1/2" or 3" deck screws. There is not much benefit to
using much longer screws, because the screws will usually break before they
pull out of the wood. But sometimes when a deck board is warped, that
extra length helps to pull it down because the screw grabs earlier.
I use a lot of 3" Deck Mate screws because they are stronger than
most other deck screws, and their square-Phillips drive works pretty
good. I find 3" to be the size I use the most because I use them in
framing a lot. That fact alone would cause me to use 3" screws, but
if you don't have a lot of other projects to use up the extra screws,
2-1/2" will work fine. These screws are a lot cheaper per pound
when purchased by the 25 pound box, but not many people need that many.
The main benefit of pre-drilling holes for deck screws, or any screws,
is simply preventing the wood from splitting. Often this is the only
way to prevent splitting when driving screws (or nails) close to the end
of a board.
It's also easier to drive the screws when the holes are pre-drilled,
especially in harder woods like oak and maple. But for the average
yellow pine deck board, pre-drilling won't make any difference because
the wood is so soft it will yield to most power-driven fasteners.
Just don't drill too far into the underlying framing lumber, or the
screw might not have enough wood to bite into.
Bruce W. Maki, Editor.