Here's how to buildan outdoor room that will weather the weather.

By Michael Haigley
September 03, 2002
 Terry Pommett

Decks make more sense in coastal locations than just aboutanywhere else. Spending time outside is the whole idea, isn't it?You want the views, the salt air, those sunset breezes.

Decks can be a bargain, too, since they expand your living spaceat a fraction of the cost of adding rooms. But plan and build themright. You know our mantra: Coastal weather, with its wind-drivenrain and withering sun, will make you pay dearly for sloppyconstruction.

You'll learn specifics from your local building codes, whichdetermine joist placement, rail height and spacing, and more. Youshould tailor the design to your needs and to the site: Is it goingto be just you and your chaise out there, or do you need it for bigparties? Are you considering the sun and prevailing winds on thedeck side of your house?

Here are deck dos and don'ts:

If you get winter snows, resist the temptation to make your deckflush with the door opening. You might save a step down to thedeck, but you'll invite built-up snow to melt and seep beneath thedoor. I like a drop of at least 3 inches.

Keep supporting posts off the ground, and anchor them securely.Even if you use pressure-treated wood, you want to minimize thechances for moisture buildup and rot. So use the pier system, whichmeans pouring a concrete pier into a hole dug deep enough topenetrate the frost line. The top of the pier sticks up 4 to 6inches above the surface.

Secure support posts with a stirrup of galvanized or zinc-platedstraps tied together, both for stability in high winds and toprevent moisture buildup. The stirrup, embedded in the pier topwhile the cement is still wet, forms a shelf that secures the postto the pier yet allows air circulation and moisture-draining spacebetween wood and concrete.

Create a drain system between siding and deck. Attach your deckso no water can penetrate through the house's outer skin. The keyis the ledger board, which is the horizontal support for the deckon the house side. Ideally, it's bolted or lag screwed straightthrough the siding to the sill structure of the house. At the veryleast, you need flashing that extends up the side of the housebehind the siding and folds over the ledger board to direct waterdownward and away from the house. But here's a simpler and betterway: I use spacer blocks of sill seal to create 3/8-inch drain gapsbetween the siding and the back of the ledger board. Sill seal is acompressible, oil-impregnated product used to seal the connectionbetween a concrete foundation and the frame the floor joists siton. I cut enough sections to tack blocks 8 inches wide by theheight of the ledger board every 24 inches or so along the back ofthe board. Then, I lag screw through the ledger board, sill seal,and siding into the structure of the house. As the board is snuggedup to the siding, the sill seal compresses and bonds to both thesiding and the board. The gaps between the blocks allow water todrain beneath the deck.