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Re: Pressure Treated Decking

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As I understand it if the 2x6 is not; T&G, sheathed over with plywood or
a similar such connection of members, than a repetitive member factor is
not appropriate.

BTW, my own home's interior subfloor consists of 1955 installed flat 2x6
T&G supported at 48" OC and it performs very well even when I had the
finished floor stripped off. I'm a pretty big guy and it felt solid
hopping up and down.  I have put tile down in some areas with just 5/8
ply screwed down plus 1/4 hardiebacker and there is no cracking
whatsoever in the tile.

Andrew made some great points and I second all of them, especially the
water proofing disclaimer note.  I agree that most if not all wood floor
systems should generally have designs governed by serviceability not
stress controlled though stresses need be checked.  Personally for this
balcony I would be thinking 24" OC supports but if the 2x6 were
installed in double or triple span pieces I wouldn't be surprised to
have 48" spans performing well.  I'm no decking guru so on one of my
projects I would be sticking with 24" OC max until the architect,
contractor or owner challenged it.

If you do some calcs you will see stress can work to at least a 5-6' SS
span.  I remember a renovation I did on an older building with existing
flat 2x6 T&G subfloor spanning 6' at an upstairs corridor, surprisingly
it felt good and solid when walked/jumped on though it did have 1"
diagonal wood flooring attached directly as a finish that probably

Donny Harris, SE

From: Drew Morris <dmorris(--nospam--at)>
To: seaint(--nospam--at)
Subject: Re: Pressure Treated Decking

The 2005 NDS (4.3.8) has the following for the incising factors:
E, Emin   0.95
Fb, Ft, Fc, Fv  0.80
Fct  1.00

These values apply when the piece is incised top a maximum depth of
0.4", a maximum length of 3/8" and a density of incisions up to 1100

I think you could also apply the repetitive factor that would offset the
incising factors some.

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