Building a Cantilevered Stairway

The first complicated job I did after setting out on my own was a set of cantilevered stairs.

Here’s a CAD model of what needs to happen. A C channel gets attached to the wall, tread supports get bolted to the channel, and railing gets fastened to the tread supports. There’s also a separate landing assembly that bridges over the stairwell to the basement.

First the C channel was lagged to the beams in the wall.

Then the tread supports were bolted to the channel. These were shimmed as needed so they were all perpendicular to the wall.

Then the railing was attached. I built the stair section in one piece based off measurements and thankfully it fit perfectly. The vertical posts attach to the tread supports with a half lap and countersunk bolts for a completely flush joint.

Later I installed the landing handrail and the basement stairwell rail.

A view from downstairs.