Laminating Stringers for Curved Deck Stairs

Swinging a tape from a wooden stake, the author lays out the inner and outer arcs of the stair at full scale on a double layer of plywood.

Then, he swings the walk line a foot inside the inner arc. Tread locations are marked at 10-inch-minimum intervals.

Chalk lines snapped from the stake through the tread marks on the walk line define the size and shape of the treads. The author verifies that the minimum tread width is at least 6 inches.

After scribing the stair on the plywood on the ground, the author makes a mirror image of the layout from a double layer of plywood, adding 3 1/2 inches — a stud width — to both edges.

He then supports the upper template on temporary posts at deck height.

Straight, wane-free studs screwed to the plywood templates behind each riser line provide a bending form.

Once built, the form is plumbed and securely braced.

Using a story pole, the author marks the tread elevations on the bending frame.

He then installs the stringer laminations, aligning the top edges with the marks and gluing and screwing them together.

Plumb and level lines mark the treads and risers.

The author makes initial cuts with a circular saw and finishes up with a recip saw to avoid overcutting the inside corners.

The author starts installation at the bottom.

The risers are made from two layers of 3/4-inch plywood lapped so as to support the front and back edges of the 2-by structural treads.

He works up the stair as high as he can until he has to remove the bending frame.

When stringers require intermediate support, the author uses tube forms to grade,

then extends the wooden posts up through the framing to double as guardrail posts.

He uses fascia material for the finished skirtboards and decking for the treads.

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