2 X 12 or 3 X 12 Stair Treads
By Greg Vanden Berge
If you've built as many stairways as I have, this is a
very simple question to answer. Should I use 2 x 12 or 3 x 12 for my
stair treads? Without a doubt I would use the 3 x 12 for a couple of
reasons.
The thickness of the three by material gives it some additional strength
and that strength could prevent someone from falling through the
stairway and getting injured. Visually looking at the 3 x 12 it gives
you the illusion that the stairway is safe. Once you start walking up
the stairway and the stairs seem solid and well constructed, it takes
the illusion and makes it a reality.
If you're walking up a poorly constructed stairway every day, not only
is it a safety problem but it takes a little bit of effort as you walk
up the stairway, holding on to the hand rail with a death grip, this can
easily wear someone out physically and mentally, over time. Stairways
should be constructed and maintained with safety as the main priority.
If you've ever walked up and older stairway that was built using 2 x 12
for the stair treads, you probably know what I'm talking about. Walking
up and down the stairway, while the stair treads are moving, does not
give you a strong sense that the stairway is safe. And of course
sometimes the stairway isn't.
For example if you have a 3 inch knot in a 2 x 12 stair tread, over time
as the wood expands and contracts, the knot can loosen up and fall out
of the stair tread, often creating a weak spot in the step. With a
thicker stair tread, it will take a little more expanding and
contracting to create a weak spot in the stair step.
If you're building a stairway wider than 36 inches, with no center stair
stringers to support the stairway, I would suggest using a 3 x 12 or 4 x
12 for your stair treads. 2 x 12 should not be used for stair treads on
any staircase wider than 36 inches.
If you choose to use 2 x 12 for your stair treads, select premium grade
lumber for safety. Try to avoid using center cut building materials and
2 x 12 with knots larger than an inch and a half. Large knots are one of
the biggest problems in construction safety.