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Prefabricated Exterior Stairs

A single unit of stair treads, risers and stringers prefabricated of concrete, wood, metal and/or polymers for access to entrances

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Want to benefit from the same efficiencies, precision, and affordability gained by buying your interior stair(s) from a prefabricator? Well, prefabricated exterior stairways are becoming increasingly available in a broad range of materials, configurations, and designs. Prefabricated stairs.Units feature easy setup and can include features like integral rails, landing platforms, and various entry configurations. Treads can be ordered in lengths from 24" to 48".

Materials available range from fiberglass reinforced plastic over a treated lumber frame to pre-cast concrete to wrought iron. One manufacturer of outside entrance doors for inground basements has teamed with pre-casters who make a prefabricated concrete stairway with integral foundation walls to use with door system.


The opportunity to cast or assemble a unit in a controlled factory environment presents economies that allow pre-manufactured stairs to compete handily with the costs of custom built stairs. Because a prefabricated unit can be used as soon as it is secured in place, unlike site built concrete stairs, installation can be scheduled over a wider time interval and concurrently with other activities.

Quality and Durability

Prefabricated stairs benefit from the ability to build them to close tolerances in a factory environment and install them in just about any weather.

Safety and Disaster Mitigation

Pre-assembled stairways can be installed as soon as the structure is framed, the foundation excavation has been backfilled, and the final grade in proximity to the entrance has been established. Once stairs are in place, workers have a permanent, safe egress to and from the house.


Most entrances that can be accessed with site built stairways can also accommodate prefabricated units. Many of the manufacturers deliver with a vehicle capable of moving the unit into place, so driving access to the location is all that is needed. The manufacturer will recommend the method of securing the unit in place and whether a footing, excavation, or stoop ledge at the foundation wall is required.

Prefabricated stairs can be priced as low as $170 for a three tread (32”), 4 riser, and handrail one side version to $850 for a precast concrete unit with a 48” deep landing to $1,500 or more for a metal 8’ metal spiral staircase with handrail.

Not Applicable

Prefab units must meet the general geometric provisions of model building codes. Stairs used for primary egress to a home must comply with provisions of the IRC that require a minimum width of 3’ and a landing on each side of the door if it used as the primary entrance. The landing on one side can be located no more than 7 ¾” from the top of the door threshold, so long as the door itself does not swing over the landing, otherwise, the distance from threshold to landing shall not exceed 1 ½”. Maximum riser height is 7 ¾” and minimum tread depth is 10”. A handrail must be provided if the stairs contain four or more risers.

Not Applicable

Some units will weigh enough to require a crane for placement in an excavation or on top of a footing. Others may only require a hard surface, such as a 4” slab. Either way, planning that is not required for built-in-place stairs is required.

Warranties vary widely because of the outdoor setting of the units where they are subjected to all types of weather extremes. Consult the manufacturer about product warranty.

Prefabricated stairs require adherence to planned topography and foundation elevation(s) in order to provide satisfactory egress. On sites where this degree of precision is possible, builders can benefit from the affordability and flexibility that prefabricated units provide.

Disclaimer: The information on the system, product or material presented herein is provided for informational purposes only. The technical descriptions, details, requirements, and limitations expressed do not constitute an endorsement, approval, or acceptance of the subject matter by the NAHB Research Center. There are no warranties, either expressed or implied, regarding the accuracy or completeness of this information. Full reproduction, without modification, is permissible.