What spacing between boards on a deck?

[dennis thompson]

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

[Stephen Musial]

With treated lumber, I butt them and it they'll shrink to a nice gap.

[Dan Friedrichs]

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.

[David Christopher]

+1 for butting up

[John Thompson]

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..

[Julian Nicks]

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.

[Mike McCann]

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

[Leo Voisine]

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

[Chris Padilla]

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?

[dennis thompson]

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

[charles lewis]

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.

[Loren Hedahl]

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.

[John Thompson]

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..

[Tom Wassack]

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

[dennis thompson]

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.

[Tom Wassack]

Dennis,
I visited the Wolmanized website (http://www.archchemicals.com/Fed/WOLW/Docs/Outdoor/Building_Maintenance_Tips_7-07.pdf (http://www.archchemicals.com/Fed/WOLW/Docs/Outdoor/Building_Maintenance_Tips_7-07.pdf)) and per their building tips, dry lumber should be gapped no more than 1/8 inch. That's close to my 16 penny nail diameter and after nearly a year of exposure and many wet dry cycles, my decking gap has never opened up enough to present a trip problem. So to answer your question, if using lumber dried after treatment, rather than wet dry lumber, I would leave some space between decking boards. Of course all is contingent on the dryness of the lumber at installation.

Respectfully,
Tom Wassack
Asheboro, NC

[Chris Padilla]

Overall, you want your wood ACCLIMATED to its environment. That is when it is at its most stable. Yeah, it'll still move if your climate has large swings between summer and winter but it should move less after it has acclimated....

[Steve Sawyer]

This thread really pees me off!

Not at you guys, certainly, but with the results I got after trying to things "right".

VERY CAREFULLY oriented the growth rings so the boards would cup down, and butted the very wet PT lumber so a gap would form as they shrank.

Like Charles above, the gaps are so small that everything and anything gets stuck in 'em, and the only way to get 'em clean is to use a pressure washer or go between every board with an awl or something. I'm getting ready to build a PT porch on the other side of the house, and I'll be putting at LEAST a nail-width gap between the boards.

Also, the stupid boards STILL cupped upwards!! Needless to say, the deck hasn't held up real well, but my dog loves to drink from the puddles that form on all the boards! :)

[michael osadchuk]

I butt the p.t. 5/4 decking and it's worked out find - no "stress" (buckling) and the rain still falls through.
The issue about "debris" not falling thru the cracks: I sweep off the seeds from a linden tree growing in the middle of the deck.

Remember, it's not only debris that falls thru cracks but also keys, that precious screw, etc. that will fall thru.....

good luck

michael

[Bob Aquino]

Overall, you want your wood ACCLIMATED to its environment. That is when it is at its most stable. Yeah, it'll still move if your climate has large swings between summer and winter but it should move less after it has acclimated....


I am putting a deck down (rebuilding actually) right now. The wood you get is very wet. If you wait till it acclimates, you will have nothing but bent and warped boards. It HAS to go down wet so its reasonably straight. I also agree with butting it up or going with a minimal gap.

[John Callahan]

Dennis, I think KDAT(Kiln Dried After Treatment) would be the exception to butting them up as Tom's experience indicates. KDAT is usually dried, iirc, to 19% or so- much drier than non-KDAT. Non- KDAT, you should probably be safe to butt them up. It all comes down to MC.

[Myk Rian]

We did our deck 20 years ago with 2x6 PT. I used a 1/4" drill bit to space them. They are now at 3/8". All the maple seeds go right through them.

[Chris Padilla]

I am putting a deck down (rebuilding actually) right now. The wood you get is very wet. If you wait till it acclimates, you will have nothing but bent and warped boards. It HAS to go down wet so its reasonably straight. I also agree with butting it up or going with a minimal gap.

Yes, you will have bent and warped boards if you don't sticker it PROPERLY: level and with weight on top. This is true for drying ANY lumber....

[Rick Gifford]

Using pressure treated limber that is wet you want to butt them tight. They will shrink and make their own gap. Otherwise a 16 penny nail is about the right spacing.

I have seen others leave a gap when laying pressure treated and wow, once it shrinks the gaps are huge!

I always butt them tight. 100% guaranteed advice or your money back. :D

[Ed Henderson]

Well, it's now 7 or 8 years since this thread discussion. I am preparing to redo a deck I built about 1990 or 91. I used nails and spaced the boards one nail width apart. The wood was spruce. I did stain the boards all 6 sides before putting them down. After installation I covered the deck with outdoor carpet. The carpet lasted about 5 years before it got ratty. I removed it and was astounded at how well the deck boards looked so left it at that. Since then I have replaced several boards that rotted. Now I want to remove the existing boards and replace them with pressure treated 2 x6 and 2x 4's.
I have been wondering if I should space them the same or butt them. I do not intend to cover them with outdoor carpet. Scraping our winter snow and ice off ruins the carpet.
I suspect that the boards I get will be a bit less solid than the boards I bought 27 years ago so they may absorb water more and faster. I do intend to stain them before putting them down but am apprehensive that when the top gets some use from feet and snow/ice scraping the boards may hold water and rot quickly.
I would appreciate some thoughts and recommendations.

Thanks
Ed

[Eric Anderson]

As one of the posters stated 8 years ago. think about your deck's location. I get a huge drop of cedar elm leaves each fall (which in Texas means August through December). They are small, and if you don't leave a sufficient gap to push them through, they will get stuck and rot the boards (I used redwood for decking material). So I leave a good 1/4" gap. If I wasn't fighting leaves, I would use a smaller gap, but I had to replace most of my decking after about 15 years due to rot from having wet leaves stuck between the boards and the elm leaves are hard to remove.

[Mike Henderson]

As one of the posters stated 8 years ago. think about your deck's location. I get a huge drop of cedar elm leaves each fall (which in Texas means August through December). They are small, and if you don't leave a sufficient gap to push them through, they will get stuck and rot the boards (I used redwood for decking material). So I leave a good 1/4" gap. If I wasn't fighting leaves, I would use a smaller gap, but I had to replace most of my decking after about 15 years due to rot from having wet leaves stuck between the boards and the elm leaves are hard to remove.
That's the same problem I ran into with composite decking. If you space them too close, the space fills up with stuff that falls off the trees. It's almost impossible to clean.

Mike

[Mel Fulks]

Plywood sloped at least 1/8 per foot and covered with glued canvas ,then painted. Lasts a very long time ,like the same treatment with boards used to. Has a long proven history.

[Phillip Mitchell]

I'm of the mind that you make the call based on the moisture content of your decking combined
with the deck's location in relation to sun, wind and rain exposure as well as any falling leaves / organic material that will inevitably get stuck in between deck boards.

I built a deck at my house nearly 2 years ago and used 2x6 western red cedar decking that was in the 20-30% moisture range at install. I spaced it with a jig using a 16d nail (light 1/8") and still have very consistent gaps that don't exceed 3/16". To me, that is the perfect spacing visually and not very much debris clogs in there. My deck has full sun, rain, wind exposure but doesn't have any trees above it close by.

Most PT decking that I've laid elsewhere has been sopping wet (water sprays out when you drive deck screws into it) that I would not space it 1/8", but the problem I've found is that when installed butted tight under those circumstances, the decking does not shrink at the same rate from board to board. Different moisture contents and grain patterns cause inconsistency, and can lead to a sloppy looking deck.

If I was using PT and cared about a consistent deck board spacing (for looks, drainage, etc) then I would use KDAT and space it 1/16-1/8" at install, expecting it to shrink a bit if exposed to direct sun.

[Andrew Hughes]

My deck is also spaced with a 16d nail.5/4 port orford cedar.The gap is a little big in the summer but perfect in the winter.The wood was dry installed in the fall.

[julian abram]

Butt them tight if you are using wet PT pine decking.

[Bill Dufour]

I think there may be some thought about snow and ice getting in and wedging boards apart if your climate freezes.

[Brad Barnhart]

we use a carpenters triangle out here in the middle of nowhere KS. It's hotter'n a scorched cat in the summer, & dry enough to burn up wheat. The winters are cold & damn little snow, but ya still got debris build up on the deck. Just drop your triangle between each board & use deck screws to hold it in place.

[Ed Henderson]

Thanks to all who have replied.
I should have given more info. I have an upper and lower deck attached together by three steps on the south side of my house. There are no tree's nearby. I live in Alberta, Canada so we do get cold weather and snow. The upper deck is 8 x 12 and I refinished it 9 years ago with cedar 1 x 6. It has a polycarbonate smoked semi-transparent cover and metal and glass railing. I used hidden fasteners and placed the deck boards in a diamond pattern. I'm quite happy with it and it is standing up very well.
I wanted to cover the area over the lower deck as well but wife says no, the kitchen would be too dark in the winter.
I also thought about using 1 x 6 cedar on the lower deck but decided not to because that would require a lot of frame restructuring. The joists are 18 inches apart. It is 12 x 12. Tomorrow I will take down the wooden rails. I want to rim the deck with one 2 x 10 and one 2 x 6. The new metal rail will sit on the 2 x 10. Then I will fill in with 2 x 4's. I should use cedar but that's expensive, but we will see.
I will space with a nail or perhaps a square( that sounds like a good method). I will check the moisture content first.
Thanks again for the suggestions. I figure this will be my last deck in this house. I am in my mid 70's. Possibly one more deck at the cottage in BC. My sons want to add a circular deck out there later this year.
Please feel free to add recommendations anytime as I will keep checking here.