Deck Stairs

Why stairs are where deck jobs fail

Most of a deck is repetition. You get the framing right once and then you do it forty more times. Stairs don't work that way. Every dimension on a staircase is checked against a number, and the numbers are tight.

The one that fails jobs most often is uniformity. The tallest riser in a flight can't exceed the shortest by more than 3/8 of an inch. That sounds generous until you remember the top riser changes when the decking goes down, and the bottom riser changes if the landing gets poured a half inch thick. Stairs have to be laid out against finished surfaces, not against framing.

The numbers that get measured

Riser height tops out at 7 3/4 inches. Tread depth starts at 10 inches. Those are CRC R311.7.5.1 and R311.7.5.2, and both carry that same 3/8 inch uniformity limit across the whole flight.

The stairway needs 36 inches of clear width above the handrail, 6 feet 8 inches of headroom, and no more than 151 inches of vertical rise between landings. On a tall hillside deck that last number is what forces an intermediate landing whether you wanted one or not.

Landings decide where stairs can go

A landing is required at the top and at the bottom, and a straight run needs at least 36 inches of depth in the direction of travel. On a sloped lot that's the detail that settles the whole layout, because you need flat ground at the bottom before the stairs are allowed to end. Plenty of hillside stair runs get redrawn once somebody measures for the landing instead of the stairs. More on hillside and elevated decks.

A handrail and a guard are two different parts

People use the words interchangeably, then build one thing that does neither job.

A handrail is required on any flight with four or more risers, set 34 to 38 inches above the nosing line. It also has to be graspable, and graspable is a measurement, not an opinion. Round stock passes between 1 1/4 and 2 inches. A non-circular profile passes if its perimeter falls between 4 and 6 1/4 inches with no cross-section over 2 1/4 inches. A 2x4 laid flat across the posts is not a handrail. It's the most common thing we get called out to replace.

A guard is the barrier that keeps you from going over the edge. It's required wherever the walking surface sits more than 30 inches above what's below it, measured within 36 inches horizontally of the edge. In California that guard is 42 inches, not the 36 the national model code allows. On the stairs themselves it's measured from the nosing line and comes down to 34 inches.

Three different spheres on one staircase

Guard openings get tested with a sphere, and a set of stairs has three rules running at once.

Nothing larger than a 4 inch sphere passes through the guard. The triangle formed by the tread, the riser and the bottom rail gets 6 inches. The open side of the flight gets 4 3/8. And if the risers are open and the total rise is more than 30 inches, a 4 inch sphere can't pass between the treads either.

None of those numbers are arbitrary. Every one of them came out of the same question about a small child.

In a fire hazard severity zone, treads count as decking

The California wildfire rules treat stair treads as part of the deck walking surface, which means the same listed-material requirement applies to them as to the deck boards. A deck built with a compliant board and stairs built out of whatever was left in the yard will not pass. Which products carry a State Fire Marshal listing is covered here: fire-zone decking.

What we build

Straight runs and switchbacks with intermediate landings. Hardwood and composite treads. Steel stringers where the span or the look calls for it. Closed risers, open risers where the code allows them, and lighting set into the risers so nobody misses a step coming back from the spa at night.

We lay stairs out on site against finished surfaces rather than off the plan, because that's where the 3/8 of an inch lives.

Permits

In the City of Los Angeles a deck needs a permit once any single point on it sits more than 30 inches above grade, and grade means the lowest natural grade underneath, not the highest. Stairs come along with the deck. If the deck is permitted, the stairs get inspected.

Call (818) 345-2866.