Things You’ll Need

  • Installation manual

  • Level

  • Tape measure

  • T-bevel

  • Saw

  • Stud finder

  • Finishing nailer

  • Finishing nails

  • 2-by-4-inch lumber

Outdoor staircase Some prefab staircases require rudimentary assembly before installation. Image Credit: Hemera Technologies/ Images

Prefabricated staircases come complete from the manufacturer. Purchasing a prefabricated staircase saves you money on carpentry costs, and installation takes less time than installing a handmade staircase. Installing a prefabricated wooden staircase involves only a handful of relatively simple steps and requires a basic set of tools. Keep in mind, however, that you must set up a landing for the top of the staircase before beginning the installation process.

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Step 1

Lay the staircase on its side and measure the length of the unit with a tape measure. Find the midpoint of the staircase and mark it with a pencil.

Step 2

Measure the angle of the staircase using a T-bevel, a gauge that adjusts to inclinations.

Step 3

Line up the prefabricated staircase with an existing landing so the top framing elements of the stairs line up with the edge of the landing. Ask a friend or family member to help you hold the staircase in place.

Step 4

Place a level across the top of the staircase and landing at both sides of the stairs to ensure the staircase is even. If not even, manually adjust the staircase until even.

Step 5

Draw a line on the front of the landing and a line on each side of the staircase while holding the staircase in an even position. Draw lines at the same height.

Step 6

Measure the height from the floor to the midpoint of the staircase as previously marked.

Step 7

Remove the staircase from the landing and place it on the floor.

Step 8

Measure a two-by-four to the height of the midpoint of the staircase. Mark the height with a pencil and cut the two-by-four to length with a saw.

Step 9

Mark an angle equal to that of the staircase on one end of the two-by-four using a T-bevel and pencil. Cut along the angle line, using a saw, to angle the end of the two-by-four.


Step 1

Move the staircase back into place, with the help of an assistant. Check that the lines drawn on the sides of the staircase line up exactly with the lines on the landing.

Step 2

Check the flatness of the transition from the staircase to the landing once more, using the level.

Step 3

Attach the staircase to the landing by driving finishing nails through the top framing element of the staircase and into the landing. Base the number of nails used on instructions provided by the manufacturer of the prefabricated staircase.

Step 4

Place the cut two-by-four underneath the staircase so the flat end sits against the floor and the angled end fits against the staircase. Drive a nail through the two-by-four and into the staircase to provide a temporary support beam.

Step 5

Locate studs in the wall abutting the prefabricated staircase if you're installing stairs against a wall.

Step 6

Drive nails through the side of the staircase into the wall studs to anchor the staircase to the wall.

Step 7

Install any brackets provided by the manufacturer of the staircase. Brackets generally assume the form of L-shaped pieces of metal that install with one side against the staircase and one side against the floor.

Step 8

Complete any finishing touches recommended by the staircase manufacturer, such as applying a varnish or waterproof finish to the surface of the wood.


Upon finishing installation of a prefabricated staircase, you may want to build a wall beneath the stairs to give them a finished look. Install a cleat, or scrap piece of two-by-four, in front of the bottom stair and nail it to the floor to prevent the stairs from slipping during wall installation.

Always follow specific instructions provided by the manufacturer of a prefabricated staircase regarding installation.


Installing a prefabricated staircase requires exacting measurements. Always measure an area for installation before ordering a staircase so you get the right size stairs.


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