How wide should my deck stairs be if my deck is 12 feet off the ground in Sussex NB?

Your stairs should be a minimum of 36 inches wide to meet New Brunswick building code, but at 12 feet of elevation, you should seriously consider building them 48 inches wide for safety and comfort. A 12-foot deck height is significant. That puts you in the range of a full-storey descent, and the stair run will be long enough that it becomes a real architectural element of your deck rather than just a quick step down to the yard.

With a total rise of 12 feet, or 144 inches, and a standard riser height of about 7.5 inches, you are looking at 19 or 20 individual steps. Each step needs a tread depth of at least 10 inches, so the total horizontal run works out to roughly 16 to 17 feet from the deck edge to where the stairs reach the ground. That is a long staircase, and if it runs in a straight line, it projects a considerable distance into your yard.

This is why most builders in Sussex would recommend incorporating at least one landing platform in a 12-foot descent. The National Building Code, which New Brunswick adopts, requires a landing for every 12 feet of vertical rise, so you are right at the threshold. Even if your local inspector does not strictly require a mid-height landing, installing one at the 6-foot mark makes the stairs dramatically safer and more comfortable. The landing should be at least as wide as the stairs and at least 36 inches deep in the direction of travel. It also gives you the opportunity to change direction, running the upper flight one way and the lower flight at 90 or 180 degrees, which reduces the total projection into the yard.

Now, back to width. The 36-inch code minimum is measured between the inside faces of the stair railings, not the outside edges of the stringers. At 12 feet up, you should think about who will use these stairs and what they will be carrying. Two people cannot comfortably pass each other on a 36-inch-wide staircase. If you are carrying a tray of food from the kitchen to a backyard gathering, or hauling patio furniture up and down at the start and end of season, that extra width is not a luxury. Going to 48 inches adds only about $500 to $1,000 in additional stringer and tread material, which is modest relative to the total cost of a staircase this size.

The stringers themselves need to be sized properly for a 12-foot descent. You will likely need four stringers for a 48-inch-wide staircase, spaced no more than 16 inches apart, cut from 2x12 lumber. After the stair notches are cut, the remaining throat depth of the stringer, meaning the uncut wood below the notch, must be at least 3.5 inches to maintain structural integrity. With 2x12 material, this is achievable with standard 7.5-inch rise and 10-inch run dimensions.

Railings on the staircase must be continuous and graspable, between 34 and 38 inches high measured vertically from the nose of the stair tread. Balusters follow the same 4-inch maximum spacing rule as the deck railing. At 12 feet of height, you absolutely want the railing to feel solid and confidence-inspiring, especially when the stairs are covered in frost or light snow during the shoulder months. Sussex gets its full share of New Brunswick's 100-plus freeze-thaw cycles, and a north-facing staircase can stay icy well into April.

For the stair treads at this height and exposure, consider composite treads with molded non-slip surfaces, or if you are building in pressure-treated lumber, apply anti-slip stair tread strips. The bottom of the staircase needs a concrete pad or compacted gravel landing that extends at least 36 inches from the last step so you are not stepping directly onto muddy ground after a long descent.

---

Find a Deck Building Contractor

New Brunswick Decks connects you with experienced contractors through the https://newbrunswickconstructionnetwork.com:

• Duguay Construction ✓
• Eastbound Homes ✓
• Hickory Dickory Decks Moncton ✓