Pier installation details (C) Daniel Friedman Deck Stair Planning
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Start here to plan for the construction of deck or porch stairs. This article defines basic stair terms: rise, run, stringer, tread and othe rcomponents. We describe options for different types of stair supporting stringers and we give advice about choosing lumber to build deck stair stringers, treads and risers.

This three-part deck stair article series describes how to build exterior stairs used at decks & porches. We include critical safe-construction details for stairs used to access decks and porches, including avoiding unsafe deck stairs and railings.

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How to Plan for the Construction of Deck or Porch Stairs

Stair gauge in position on a wood scrap (C) Daniel Friedman

Stairs are primarily functional elements, but they can also have a large impact on the visual appeal of a deck. They can be prominent and grand, or minimal and understated.

Sometimes the site and deck style dictate the type of stairs you need; at other times you have a great deal of latitude in the design. Either way, stairs can be a major component of your deck’s appearance, so take some time to find a style that suits you.

One of the most visible parts of a stairway is the railing. Whether you are required to include a railing or just want to have one, be sure to include the railing in your overall design.

Likewise, lighting the stairs and the landing is an important safety consideration and may be required by your local building codes.

Stairs with three or more steps should have a railing on at least one side. The railing must be located 30 to 38 inches above the nosing on each tread. Railing posts must be spaced no more than 5 feet apart, and balusters must be spaced no more than 4 inches apart. Deck stairs are frequently built without risers, but codes often require them, and many people think stairs also look much better with risers.

To help keep children or pets from falling through, the triangular area formed by the tread, riser, and railing must not be large enough to permit a 6-inch ball to pass through. The stringers should be attached to a concrete pad, and the stairs and landing may have to be illuminated.

Stair Support Components: definition of Stair Stringer

The basic framing components of stairs are stringers, also called carriages. Typically made out of 2 X 10s or 2 X 12s, stringers are often cut to create level surfaces for treads and plumb surfaces for risers. Stringers can also be solid boards with brackets attached for the treads. Stringers can be attached to the deck framing and the landing pad with angle brackets.

The treads and the risers are related components. Treads are the part you walk on. Risers, if any, fill the vertical gaps between treads.

How to Determine the Stair Dimensions: definition of stair rise, stair run, stair tread dimensions

Stair rise and run sketch (C) Daniel FriedmanRegardless of how you plan to build your stairs, you must first calculate the overall dimensions. In the terminology of stair building,

  • Stair rise is the vertical distance or height that the stairs will ascend from the lower walking level to the upper level.

    The total rise is the vertical distance the stairs must travel from the landing to the deck surface. The measurement should be taken directly over the landing pad, not off the end of the deck. Use a level or 2 X 4 to extend the deck surface over the pad, then measure the total rise from the pad.

    The next step is to calculate the unit rise (the vertical distance from one tread to the next). Let’s assume that the total rise is 32 inches. Divide that figure by 7, which is an ideal unit rise. The result, rounded to the nearest whole number, is the ideal number of risers (5 in this example).

    Now divide the total rise (32") by the number of risers (5), to determine the actual unit rise (6.4 inches). You might find a rise of less than 6 1/2 inches to be too short, in which case you could reduce the number of risers to 4, resulting in a unit rise of 8 inches but that step would be a bit tall and not ideal.
  • Stair run is the horizontal distance over which the stairs will traverse in the course of the ascent or descent. When building deck stairs, unlike interior stairs, you are usually not pressed for space, so you can plan for a convenient and comfortable tread depth.
  • Stair treads are the walking surface of the stair. Stair tread width is the long-dimension of that walking surface and will be close to the stairwell width. A good stair width is 36". Stair tread depth is the distance from the front or nose of the stair tread to the back edge of the stair tread. Typical stair tread depth is around 10".

    Framing tip: when planning stair tread dimensions keep in mind that if your ideal tread depth is a dimension that is just slightly more than available lumber you may have to purchase and waste much of larger sized boards. Using treated 2x lumber for exterior deck stairs remember that a 2x12 is not a full 12 inches in width - more like 11 1/4 to 11 1/2. Measure the actual lumber width available.

    We explain more sources of variation in stair tread width at DECK STAIR BUILDING DETAILS.
  • Stair risers are vertical boards that enclose the openings between stair treads in a "closed riser" design. In open riser stairs there are no riser boards installed.

Details about how to calculate the stair rise and run are given at STAIR RISE & RUN CALCULATIONS.

Stair Stringer Options

Stair stringer options (C) InspectApedia Carson Dunlop AssociatesMuch of the variation in stair styles boils down to how you handle the stringers. The easiest stairs to construct use solid stringers with metal brackets supporting the treads, and no risers. This style is best used on short, narrow stairs or where risers are not required.

Cut stringers involve more effort, but they result in stronger, more attractive stairs.

They also provide a solid vertical surface for attaching risers. If you want to build stairs with cut stringers, but prefer the profile of solid stringers, you can add a decorative trim board.

Illustration at left provided courtesy Carson Dunlop Associates.

Deck Stair Landing Choices

The landing is a very important consideration for any stairway, since it provides a firm surface for the first step up or the last one down. On decks, the landing also serves as support for the stringers. The best type of landing is a concrete pad. With careful planning it is possible to pour the pad while you are working on the footings and piers, but it i% safer to wait until the decking is installed.

The bottoms of the stringers are usually attached to the landing pad with angle brackets. Alternatively, the stringers can be cut to fit over a 2 X 4 kickboard fastened to the pad. For short stairs, you may be satisfied with a landing of compacted gravel; attach two 2 X 4s across the bottoms of the stringers to distribute the load.

Choose the lumber size

 Short deck stairs can often be made with 2 X 10 stringers, although many builders routinely use 2 X 12s. The critical determination is the minimal width left in the board after the notches have been cut. If this width would be less than 4 inches you should use wider boards for the stringers.

To determine the length of boards you will need for the stringers, use your framing square and a tape measure, and assume that 1 inch on either represents 1 foot. On many squares, one edge of the square is graduated in twelfths of an inch to facilitate this calculation.

Figure the total rise and total run in terms of feet and inches, then mark the total run on the long side of the square and the total rise on the short side.

Determine the distance between the marks with a tape measure to determine the minimum length of the boards you will need.

 

Continue reading at DECK STAIR BUILDING START or select a topic from the More Reading links shown below.

Or see DECK STAIR BUILDING DETAILS

Or see DECK & PORCH CONSTRUCTION - home

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