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Thread: What spacing between boards on a deck?

  1. #1
    Join Date
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    Question What spacing between boards on a deck?

    I am going to build a deck out of pressure treated lumber. I've read various opinions on the spacing between boards....some say to butt them because they will shrink....others say to leave the space of a nail between the boards. What do you do?
    Thanks
    Dennis

  2. #2
    Join Date
    Oct 2008
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    Webster Groves, MO
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    With treated lumber, I butt them and it they'll shrink to a nice gap.

  3. #3
    I've built 3 decks with cedar - the first two, I left a small gap between the board (I built a small jig to space them and align the screws on each board). The third deck I butted them together. The ones with the spaces now have clearly larger gaps from the boards shrinking. The one that I butted together now has reasonable spaces for water drainage, etc. This was with cedar, not PT, but my mind is made up: Butt them together and let them make their own spaces!

    I suppose the success of this depends highly on how wet the wood is when you use it.

  4. #4
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    +1 for butting up
    Dave

    IN GOD WE TRUST
    USN Retired

  5. #5
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    Butt em.. the first deck I built with PT I didn't and I replaced it a few years latter the gap was so wide. Women rarely wear high heels anymore but back then that was outright dangerous to have a large gap. The PT will definitely shrink in the sun.

    Sarge..

  6. #6
    I find it funny that when pt lumber was introduced they said to space it with a carpenters pencil. Those decks were toe breakers once the boards shrunk, and the spaces ended up over 1/2" wide!

    Never space cedar or pt lumber, since it will shrink more than expand. You only space engineered decking, and even their specs are too much IMO.

  7. #7
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    I vote for butting them together they will shrink. If going with composite i would space them

  8. #8
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    East Freetown, Ma.
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    My first deck I used a nail space - now - the spaces are so large that acorns can fall through.

    Every deck after that I butted - and the spacing is OK

  9. #9
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    Get 'em nice and tight to each other...as if you were gluing up a large panel from several smaller boards....

    If you have the time and space, sticker the lumber to let it dry a bit and shrink before installing....

    What kind of deck system are you using...if any?
    Crown Molding: cut, cope, cuss, caulk, chill....

    Did you know SMC is user supported? Please help.

  10. #10
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    Thanks for the info....I'll definitely butt them. I'm not using any system just wood, hangers & screws.
    Dennis

  11. #11

    For the gap

    I guess I will have to disagree , its a matter of preference my first deck I butted them together living on the Oregon coast amongst pine trees needles , maple seeds, leaves etc. would plug the gap when the rains came the gap would shrink and not allow the water to drain off.
    If you don`t have debris problems it would probably be fine, three decks since at least everything falls thru and much easier staining etc.
    Charles Lewis

  12. #12
    Join Date
    May 2006
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    Puget Sound area in Washington
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    Taking into account that I live in Western Washington when I built my deck of redwood the advice was to space them 1/4 inch. I made a jig of 1/4 inch plywood to do this.

    I suppose the spacing is a little larger by the end of our dry summers, but I am happy with the results. Because we have fir and hemlock trees nearby as well as a white birch overhanging the deck, by spring the gaps are quite clogged with debris. The 1/4 inch gap makes for easy cleaning with a garden hose and small scraper tool. It also allows for good air circulation to promote drying.

    Decks I see locally that were built with butted planking are difficult, if impossible, to clean well and seem to succumb to rot before their time.

    So to gap or not to gap -- the location may be the deciding factor.

  13. #13
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    Quote Originally Posted by Loren Hedahl View Post
    So to gap or not to gap -- the location may be the deciding factor.
    I can't speak for the use of cedar Loren but.. I can speak for the use of PT which is often dripping wet. It's going to shrink and especially in an area as here in Atlanta where you get droughts in the summer along with a very hot sun. Your area has the monsoons so... you are correct in that location may play a role.

    But... moisture content of the wood used off the shelf is going to play a large role also and wet PT shrinks big time. The first deck I built with it I gapped with a 1/8" piece of stock. 6 months latter the boards side by side had shrunk enough to leave almost a 3/4" gap. If you do any formal entertaining where women might have heels or people wear flip flots... you can have a heel drop through and break an ankle or a toe drop and break it. Ask my son about that theory.

    I totally agree that is harder to clean debri from a larger gap but.. on the other hand you raise the risk of injury and a liability suit file against you. I butt mine.. use a leaf blower often and just clean what is left. So.. location is just one factor IMO that has to be considered I believe.

    Regards...

    Sarge..
    Last edited by Chris Padilla; 06-18-2009 at 4:21 PM.

  14. #14
    Join Date
    Jun 2007
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    Randolph County (Asheboro, NC)
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    PT Decking

    Greetings from NC!
    Having just a built a deck last summer, I started out butting the edges of Wolmanized SYP that had been dried after treatment. During the decking installation (20 or so boards already installed), we had several days of afternoon thunderstorms. The installed boards were under a lot of stress from taking on moisture from the rains. So much so, that a length of decking between two adjacent pieces had to be pried up after removing all screws. I readjusted the already installed boards to remove the stress and gapped my still dry and uninstalled boards the thickness of a 16 penny nail. Therefore, I think the decision to gap also can be influenced by the moisture content of the decking.

    Respectfully,
    Tom Wassack
    Asheboro, NC
    Last edited by Tom Wassack; 06-18-2009 at 3:32 PM.

  15. #15
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    Tom
    Your comment about the thunderstorm causing the boards to expand as they absorbed moisture makes me wonder if I actually should wet the boards before I install them butted up, what do you think?
    Dennis
    PS I called the Wolmanized wood people & the technician was very helpful & said to butt them up.

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