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How to Build a Spiral Staircase

Learn how to build an outdoor spiral staircase that allows people to go from upper to lower deck without going inside the house.

More in Outdoors

  • Time

    Several Weekends

  • Price Range

    $2,500 - $5,000

  • Difficulty

    Hard

Highlights:

Step 1: Decide Where the Staircase Will Go

Start by placing a pre-poured concrete slab where the base of the stairs will be (Image 1). (This will not be necessary in all cases.) Since this spiral staircase is coming off of the existing deck, we need to build a wooden template of the metal upper deck platform. Since the center support pole will be on the edge of the pad, we have to determine where it will land at the bottom. A plumb line ensures us an accurate calculation of where the pole's base plate will go (Image 2). If necessary, remove some of the railing around the porch to make access to the staircase (Image 3). (This will not be necessary in all cases.) Use a drill and a hammer to remove the spindles of the railing, but leave the handrails for support.

Step 2: Install the Pole

Once the plumb line has determined where the base plate will go, trace a circle around the base plate on the concrete slab. Also be sure to mark where the holes for the lag bolts will be. Drill pilot holes into the concrete where the lag bolts will go. Insert plastic anchors into the holes and ratchet the lag bolts into place, securing the base plate. Slide the pole into place on the base plate. The pole may need to be hammered into place to ensure that it is securely attached to the base plate.

Step 3: Insert the Risers

Slide each riser onto the pole, alternating each step from side to side to maintain balance and weight distribution. Once all the stairs are on the pole, slide the upper deck platform into place (Images 1 and 2). Level the platform in all directions and then bolt it to the joists under the deck. Next determine the rise measurement, first measure the length of the pole from the floor to the upper landing. Then divide the distance by the number of steps. That determines where each riser will be installed. Then bolt each riser into place and tighten with an Allen wrench. Make sure each riser is level. Once the last riser is bolted into place, drill pilot holes into the concrete pad to secure the poles plate. Use lag bolts to secure the plate firmly into place.

Step 4: Attach the Handrail

Unfurl the metal handrail into the diameter of the staircase (Images 1 and 2). Once the diameter is reached, pull the handrail the distance of the staircase. It doesn't have to be exact, slight adjustments can be made later. Three spindles are added to each step and wrenched into place. The handrail is screwed to the top of each spindle. Use a hacksaw to cut the guard rail to the appropriate size. Secure the guard rail into place on the existing railing of the upper deck. Remove the original handrail from the entrance of the staircase.

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