The Joy of Wood: A Staircase Saga, Part 6: The First Two Curving Treads.

All this year I have have been privileged to be working on a big renovation, where I have been doing a wide range of carpentry and joinery work. An Art Deco home built in the 1930's, the house has been expanded upwards and outwards. The addition of a second storey brought about the need for a staircase. Another job for me, which I relish. Stairs are a wonderful brain challenge and have always been a great chance to push and test my skills.

Where possible, the old original jarrah roof timbers removed to make room for the top storey are being recycled back into the house by way of the staircase, window sashes, and many other uses. Most of the straight treads in the stair case are made from glued up rafters from the original roof.
Yep, it ticks all the right boxes...

Previous posts tell the story of the Staircase Saga thus far:
Part 1: Building a Staircase with Winders.
Part 2: Getting Started.
Part 3: The Big Flight.
Part 4: The Short Flight.
Part 5: The Winders.

It seems that somehow I don't have a pic of the staircase with the winders completed which shows the missing first two treads.

Winders completed... now for the first two treads.

In the pic above, the lowest tread in the foreground, is tread number 3. Completing the winders meant that treads 3 to 20 are done. There is still the handrail to do and a few bits of trim around the wall edge of the winding treads - however the priority now was to make the first two treads.

The original architect's plan, showing the first two treads poking straight into the entry hall.

In the original plan, these first two treads were going to stick straight into the entry hall. Discussing this one day, we hit on the idea of making these treads flow out into the room by both curving around to meet the walls on either side. It seemed like a really good idea! Another fantastic challenge for me, and I was looking forward to bringing the concept to reality.

Planning the curving treads.
If you have been following this saga, you won't be surprised to find I start out with a set-out board with a full scale drawing. It was important first to transfer the positions of the newel posts, walls and other key features onto this board. In this house which is 80 years old, not many of the original walls and floors are square or plumb. I needed to record all this on the set-out board, as everything would need to be scribed to fit the existing floors, walls, and staircase structure.

Part of the full scale drawing board, showing the right hand end.

Never mind the walls and floors, the staircase was all being built to be square and plumb to the planet! So allowances for scribing and fitting would need to be made to all components. All of the winders in the first set were radiating from the same theoretical point in the newel post. The curves would also be drawn from the same theoretical point and from a similar position on the other end. The use of these points and careful marking out would enable the creation of a set of very accurate templates for various components for the two treads.

Formers, riser boards, and nosings.
I needed to decide upon the method to be used to make the curved riser boards. Years ago, I used the multi-kerf method to bend jarrah sides for a couple of coffins I built. I reckon that would be the way to do this. So I did some testing.

A rough test, but it was going to be a winner.

Using my trusty radial arm saw, a series of saw cuts were made across the stick (165mm (5 1/2") wide, leaving approx 2mm of material uncut. These kerfs were cut where ever the curve would be formed, plus about an inch either side. This way one continuous stick (19mm thick) would be wrapped around the face of each former to create the riser boards.

Cutting the kerfs with the radial arm saw.

The formers were made using 16mm (5/8") plywood and bits of jarrah.

Making up the former for Tread 1's riser board.

Lining blocks were glued top and bottom between the radial ribs - just like the inside of an acoustic guitar.

Former with lining blocks ready to have the riser board attached.

You can never have too many cramps! Gluing the riser board to the former.

The riser board has a rebate running around the top edge, like a continuous barefaced tenon running full length around the top. This would be housed in a groove running full length of the nosing 15mm behind the front edge of the nosing.

Gluing a couple of layers of thick jarrah veneers to the back of the bottom edge of the riser board.

The former for Tread 1 was made 20mm short of the width of the riser board, to allow for scribing of the riser. There was a 12mm (1/2") fall in the floor from one end to the other. This 20mm protrusion was strengthened by gluing a couple of 2mm thick veneers around the curved sections.

The nosing for Tread 1 being glued up in its segments.

Each segment joint in the nosing had 6 dowels and a biscuit held with epoxy resin! Cramping it up was tricky, but worked well.

Accurate templates and the router with a long flush-cut bearinged bit would cut the sweeping curves in the nosing.

The rebate cut on the inside would hold the tread insert behind the nosing.

The groove cut on the underside of the nosing, to house the riser board.

The two tread units completed and placed in their stack - except for the inserts.

Tread inserts cut to fit. Time to do the installation!

The tread units were now complete, and ready for installation. This was going to be a tricky job, as everything would be to be scribed to size and position and fitted.

Installing the two tread units.
First I had to sand the floor in the immediate area to get the floor area ready.
Then I had to scribe the bottom unit (Tread 1) to the floor and walls.

Cutting the horns to length to achieve a snug fit to the walls.

Scribing the riser board to follow the contour of the floor.

The bottom unit was leveled using packers, and scribed to the floor contour using the old trick of a block of wood and a pencil at the lowest common denominator. It is as accurate as the cutting to the line, which was the next stage. It worked a treat, using my rusty hand saw and jack plane. With much checking of the measurements and position, Tread unit No 1 was screwed to the floor. Unit 2 was then made to fit the walls, and fixed to both Unit 1 and the wooden staircase structure in the correct position.

The inserts being fitted to the treads. These were nailed into place.

The final fixing job required me to climb in through a small hole in order to screw the top riser board to tread insert 2, from behind. It was a squeeze but a great moment. This complex and demanding task was completed!