The inspector that inspected my house wrote the following in my inspection
"The decking is installed with no voids between the planks for drainage and
most of the planks are upside-down (with the grain crown down). The
builder stated that the planks will shrink to provide the gaps, and that
the "good" side of the planks is facing up."
I know that a few cycles of thermal and moisture expansion and contraction
may leave a gap between the planks over time, but will it be sufficient for
drainage? Also, the builder does not want to reinstall planks with the
grain crown up. However, I believe this should be done on a new house. I
have read that incorrect installation of these planks increases the chances
of splintering since one side of the wood is more susceptible to this.
However, I need some firm ground to stand on. Does anyone know of any ASTM
standard or equivalent that might address this, or any web sites?
On Fri, 07 Nov 2003 00:46:21 -0500, Matt Oliverius
No standards, and no general consensus anymore as to which is best.
If this is PT lumber, it may not shrink enough to provide gaps, but
cypress and redwood usually do fine. The theory is that boards will
warp away from the crown, and if the crown is down the edges will warp
up and the board can retain water. In reality, boards will warp
toward the crown on occasion, and if the boards are fastened well they
don't warp appreciably enough anyway.
If you're concerned, switch to a non-wood decking. I'm assuming this
is a home inspector, not a building inspector, and he's covering his
butt in case the boards warp and you blame him for not telling you.
My inspector was very good, but I got notations about a fence latch
that was slightly crooked, roofing that "looked" old but didn't show
any physical aging signs and touch-up paint that didn't exactly match
the wall color.
What type of wood, what size, how far away are your joists, and how
are they fastened, nail or screw. PT shrinks if its 2x4, crown down
will cup and hold water, 2x4 not much though, are all boards reversed,
or did he just not check them. Screws are best
Thanks for the info everyone. I had heard about the cupping of wood planks
if they are installed with the grain crown down, and the potential for
I found a website last night that explained it very well. "Flat grain
lumber tends to exhibit grain raising. When the grain separates on the
face of flat grain lumber, it occurs on the pith side or "heart" face of
the board. To prevent grain raising problems, the most important
consideration is to orient boards so that the bark side will be exposed to
the weather. Deck boards should always be installed "bark-side-up" and
siding should be installed "bark-side-out" whenever possible."
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