How to Lay Out Deck Stair Stringers

After talking to many deck builders over the years, we have found that stair construction is considered the most difficult part of building a deck. In order to find the right stair stringer layout for your stairs, you first need to measure the exact height of the deck from the top of the decking to the location where the stairs are going to land on the ground. You can input this number into our Stairs Calculator on Decks.com. The calculator will provide you with the number of stairs, riser height and tread depth to cut your stringers. You will need to remove the thickness of the riser board from the top stair and remove the thickness of the tread board from the bottom stair. You can now draw the notches for the stairs onto your 2×12 stair stringers. The difference between the stair rises and tread depths cannot vary by more than 3/8″ from the largest to the smallest.

How to Anchor Deck Stairs to Concrete

Stair stringers should always land on a level and well-drained surface. If you are landing on a concrete pad or a patio, this should not be a problem. However, if you are landing on the yard, you may want to install paver blocks or fill the area with compacted gravel to promote drainage. Make sure you are using .60 retention pressure-treated wood that is rated for ground contact. You should install footings at the bases of the stringers to prevent frost heave. This is not always required, but we seriously recommend it. With frost footings in place, you can use a concrete anchor, base plate and short post in order to create a solid ground connection. A 3′ x 3′ level landing area is required at the base of all staircases. The ground may qualify if it meets the requirements. 

Extra Support For Long Stair Stringers

If your stringers are more than 10’ long, we recommend installing a rigid beam at mid-span to add support to the structure. The strength of stair stringers is considerably weakened by the cuts made to create the stair surfaces, and stairs must be strong enough to withstand heavy foot traffic and very stressful conditions. Both visually and structurally, it is preferable to break long stair runs with intermediate landings. In some cases, however, you may need to use one long run.

Stair Stringer Attachment

How you attach the stair stringers to the top of the deck and to any landings will be critical. You should reinforce the rim behind the stairs to provide a solid base for attachment. Use positive connections to install stair stringers using stair stringer connectors to the front face of the rim to provide adequate support. If your first tread steps down from the deck, you must extend the rim joist to create a solid surface below the deck rim to attach it to. You should attach 2×6 or 2×8 support framing under the rim flush to the bottom of the stringer. 

Closed Stair Risers

Most high-end deck projects use closed risers to finish the stairs. Open risers sometimes appear cheap and unfinished. They also are often in violation of IRC code for decks over 30″, which maintains that they meet the same requirements as guardrail infill. Stair risers may not have openings present that would allow a 4” diameter sphere to pass through. Most risers are made from deck boards or fascia material. Make sure the material is heavy duty enough to resist feet kicking the risers. If you are using 1x material, you may want to install blocking behind the riser board for added strength. Low-voltage lights can be installed into the riser boards in order to meet the IRC code for stair illumination. Most deck stairs use a nosed tread that extends beyond the riser board, which looks attractive and protects it from being kicked loose from above.

How to Cut Deck Stair Stringers

The stair stringers are essentially the backbone of your staircase. Always use straight, high-quality, pressure-treated 2x12s for stair stringers. If you are planning on resting the stringer on the ground, make sure the wood has .60 RET level. You want the crown side of the board to be on the cut side.In order to prepare the stringers, you will want to lay out one of your 2x12s on saw horses and use a framing square and clamps to trace the outline of the stair using the information from the Decks.com Stair Calculator. If you line up the riser height and tread depth on the framing square and align it to the stringer, you will be able to find the exact angle to cut your stairs. Repeat this process along the stringer. Because the bottom step will be the ground, you will find that it will be too short by the height of one tread. After the stringers have been marked, you must make an adjustment. Drop the stringer by cutting off the thickness of one tread to adjust for landing on the ground. Depending on how you are attaching the top step, you may need to make an additional adjustment to maintain a uniform stair design.

How to Lead Deck Stairs to a Patio

Decks are often built before patios in order to allow frost footings to be placed without disrupting the concrete slab. It is best not to attempt building both projects at the same time so you can focus your attention on the job at-hand. If you are planning on installing a concrete patio below the position of your stair landing, you will need to adjust your stair design to properly land on it once it is completed. You may need to postpone your final deck inspection until the patio is installed for the stairs to meet the uniform riser and tread requirements. In the meantime, you should brace the bottoms of the stairs. 

Building Cascading or Wrap Around Stairs

Cascading stairs are a popular style of staircase that wraps around the corner of a low deck. This is an attractive and extremely functional approach to deck design and stair construction. However, tall cascading steps can begin to look awkward and present a tripping hazard. If the drop requires more than about five steps, you may want to use a conventional staircase.

Stair Tread Nosing

When building your stairs, it usually works well to use two deck boards to build the stair tread. The tread is the part of the stair that you walk on and is held in place by fasteners mounted to the horizontal surface of the stair stringers. When installing the tread, many builders project the front end of the deck boards over the stringer by the thickness of the riser as well as about an inch as a nose. This projected step helps protect the riser from becoming loosened over time. It is a nice detail that adds definition to the stairs. It is usually most attractive to use a radius edge or bull nose face for the stair nosing. Most 5/4 wood decking is sold as radius edge. If you are using 2×6 that has a square corner, you can use a router to round over the edge.

Deck Stair Lighting

Believe it or not, IRC code requires that you provide lighting for your deck stairs. It is rare that stair lighting is ever inspected because deck inspections take place during the day. In most cases, your exterior light beside your patio door will be sufficient. However, there are a number of easy lighting solutions that can add a unique design element.