Tips for decking?

June 8, 2010 2:01 AM

What mistakes are we likely to make when laying our new decking? What are the best practices for getting this done nicely enough that we don't regret it when we look at it a few years down the road?

The boyfriend and I are in the process of rehabbing my small (10'X10') deck; we've finished dealing with the framing under the deck and are ready to lay a full set of new decking- a bunch of pressure-treated 2x6s.

We are particularly concerned about the correct spacing; we are getting conflicting reports about whether it is best to butt pressure-treated wood straight together, or whether we should space it (and if so, how much). If it matters, we live in a moderate climate- about 16" of precipitation a year, although a big chunk of it is in the form of snow that I have historically been too lazy to shovel off the deck.

Difficultly level: neither of us are super-handy, but we are both fairly detail-oriented and are capable of following directions. Any general tips or tricks are greatly appreciated!

posted by charmedimsure to Home & Garden (18 answers total)

When we laid down our deck, I believe we spaced it using a thick nail for a spacer. Easier to clean, no worries in the winter, clean, consistent look if you make sure it's applied evenly.
posted by disillusioned at 2:24 AM on June 8, 2010

It depends on how wet the decking boards are. Wood expands when it absorbs water and shrinks when it dries out. Your decision depends on whether the wood is now drier or wetter than it will be once it arrives at its EMC (equilibrium moisture content). If it's currently rather wet then it will ultimately dry and shrink, in which case you can install them very close together so that the gaps will not get too wide as the shrinkage occurs. If the wood is already very dry, i.e. has been stored indoors or in direct sun with lots of air circulation for a long time, then you need to leave more space between the boards so they have room to expand.

There are some expensive exotic woods popular for use in upscale decks that are sold kiln-dried and which definitely need room to expand. Treated lumber is often very wet (heavy!) when purchased, so it's much more likely to be okay to space yours more closely.

Tangentially, the 2x stock is usually only used for the framing. Your lumberyard should have thinner, nominally "5/4" treated decking that is 1" thick. It tends to have fewer knots, and rounded corners which are nicer to your feet.
posted by jon1270 at 3:02 AM on June 8, 2010

If you're using wood (as opposed to composite) decking, err on the side of wider gaps than narrower. Decking must be able to breathe on all sides or it will not last, pressure treated or no. Narrow gaps can fill up with dirt or detritus, preventing drainage, giving insects a home, and allowing water to stand -- all of which accelerate failure. As jon1270 says, if the boards are wet, fresh from the treatment facility, or were stored under a tarp in a damp climate, space them closer together so they will dry. If they're really dry, space them farther apart.

In general softwood can expand/contract 3-6% across the grain from dry to damp, and can get even bigger when saturated. So if you're laying 6" boards, nominally about 5" wide, you should figure 5% of that width as how much the wood will change across the seasons unless you're in a dry climate. 5% of 5" is a quarter of an inch.

You also need to make sure the boards are at least 1/4 to 3/8" apart at all times for good drainage and shedding of debris. So if the boards will move 1/4" and need 1/4" spacing at a minimum, then depending on whether your boards are currently wet or dry dictates whether you'll use 1/4" spacing or 1/2" spacing.

Since most Pressure Treated lumber is sopping wet freshly treated (it feels cold to the touch) from the lumberyard, the nail spacing is an acceptable rule of thumb. Lay boards next to each other then jam a nail between them. (Do not do this if the boards are not almost dripping wet; you need more space if they're even somewhat dry.)

Anyway, now you know where that number comes from, and you can assess spacing based on your own lumber and climate.
posted by seanmpuckett at 4:45 AM on June 8, 2010

According to Hometime:

If the deck boards are relatively dry, use 16 penny nails to establish the proper gaps between the boards.

Proper spacing allows moisture to drain off the deck between the boards.

Wood expands when it's wet. If the boards are wet when you install them, you can probably butt them close together without any gap. They should shrink as they dry out and produce adequate gaps between the boards.

Dean Johnson is a good Minnesota boy, so I'm sure his instructions take snow into account.
posted by ob1quixote at 4:58 AM on June 8, 2010

Having built few of those, I always left a 1/4" gap. Another thing you might consider is laying the decking down at a 45 degree angle to the framing. It's stronger, and somewhat decorative.
posted by StickyCarpet at 5:27 AM on June 8, 2010

I have evolved my deckfu over the years. Now, I use stainless steel screws to fasten it, rather than nails. Also, try to lay it out, so the spacing results in not needing to rip any of the boards. And if you do need to rip one, do it closest to the house, to in the least visible place. And yes, plenty of spacing, and keep debris out of those spaces.
posted by Danf at 5:38 AM on June 8, 2010

You're getting some pretty good advice here - if you use weatherproof screws instead of nails, and predrill your holes, use pressure-treated lumber and seal off the cut ends of it (with a treatment product you can buy at any lumberyard) then your deck will last you twenty-five years.

Space your boards about a quarter inch for drainage and expansion's sake, I say, and make sure that the underside of the deck has a way to drain water properly so that rainwater won't stagnate anywhere, and you should be fine.
posted by mhoye at 5:54 AM on June 8, 2010

I should add - if you're building a railing yourself, or anything that requires evenly-spaced boards, don't eyeball it or measure it. Build yourself a jig of some kind instead, so you can get consistent results without having to measure or guesstimate every time.
posted by mhoye at 5:57 AM on June 8, 2010

When we resurfaced our deck, we had the builder do the usually thing, which is to screw the deck boards through the surface. I kinda regret that, as it looks a little bit rough, though typical for a deck.

I wish we had used one of the undermount systems where you screw from the underneath or from the side, which leaves the board surface looking nice and clean. This is the one I think I'd try to use, if doing it again : Kreg Deck Jig. ( no affiliation with Kreg.) I know thatLee Valley Tools carries it, among other places.

Also, nthing the concern about moisture content. The boards we got were pretty damp, and the gap between planks opened up noticeably after 3 months or so. Not so much we had to do anything about it, but enough to notice.

We did manage to wait long enough to put a penetrating oil stain on, which was about 3 months for us ( ask your dealer/read the can). If the boards have too high a moisture content, then that type of finish may not penetrate well, and form a skin on the surface instead.
posted by toddje at 6:08 AM on June 8, 2010

Use a chalk line to lay out where your screws should go. It really makes a normal deck look "pro" when it all lines up nice. Pre drilling (and dumping some sealer into the holes) will also add to longevity.

Another nice thing would be to chamfer the cut ends of the boards.

And yeah, seal up the ends real good. End grain absorbs moisture a ton, and you should keep putting coats of sealer onto the ends until it stops absorbing it.

If you are going to stain it, use *stain* and not that crap that looks like paint. I forget the name of it- it's the kind without solids in it. Then use a purpose-built sealer afterwords. And stain/seal the boards before you install them so the undersides get treated too.
posted by gjc at 6:10 AM on June 8, 2010

Another thought might be to grab a plane and plane off any splinters that come off after screwing it down. If I was really nuts, I'd run a belt sander over the boards to get them nice and flat.
posted by gjc at 6:13 AM on June 8, 2010

Convex side up, concave down. (I know you know that, but you might oversee it in the doing.)
posted by IndigoJones at 6:45 AM on June 8, 2010

Definitely use screws, not nails. Definitely put a coat of sealant on it, and reapply about every other year or so.
posted by kjs3 at 6:48 AM on June 8, 2010

While using a nail is cheap and handy it's also a pain in the ass (ever tried to hold a nail while pushing a board against it and then driving a screw/nail? you are short about two hands). A strip of hardboard/plywood the right thickness will lay across several joists and hold itself in place. And it can be used as a guide for fasteners.
posted by Mitheral at 7:41 AM on June 8, 2010

Make certain you have a big enough gap between the boards. Our gaps were not made big enough so they quickly get clogged with dirt, dog hair, tree debris, snow and ice. The debris is hard to clean out and it holds water, which can damage your wood and stain.

I'm sure they used nails as spacers when they built our deck, but either they weren't big enough or the boards swelled up a lot afterwards.

Also, use screws that will never ever rust or corrode. They're expensive but worth it. After about 15 years we're suddenly having a lot of problems with boards popping up because the old-style metal deck screws are rusting through.
posted by 14580 at 9:14 AM on June 8, 2010

Use masks when cutting pressure treated lumber. Sweep up all sawdust and dispose of it properly. Do not ever burn pressure treated lumber. Using a preservative for wet lumber will help it dry more slowly, helping to prevent splitting and cracking. The EPA suggests using a penetrating oil finish to lessen human and animal exposure to CCA.
posted by oneirodynia at 10:02 AM on June 8, 2010

I've built a lot of decks with pressure treated lumber. Using 2x6 as decking will make it very strong. Seconding convex side up. Just look at the end of the board for the frown- as opposed to the smile. A round-over bit on a router works nicely for the edges of the boards and the ends. If you do use screws on the surface it may help to pre-drill the holes with a 1/8" bit.

Seconding do not burn scraps, repeat, do not burn scraps!
posted by mareli at 11:15 AM on June 8, 2010

Thanks, everyone! I feel like we have a good idea of the direction to go now.
posted by charmedimsure at 1:27 PM on June 8, 2010