Sunday, June 16, 2013

A Staircase Saga, Part 2. Getting Started.

This a bit like the Star Wars movies saga. The first post I did on this Staircase Saga came midway through the story, and now we have gone back to the beginning with this, the second post!

Getting started.
First you need somewhere requiring a set of stairs. My customer has been doing a renovation on her lovely Art Deco double brick and tile home from the 1930s. This has involved extending out the back and going up - putting on a second storey. Hence the need for a staircase!  I have the plans, but plans are always theoretical. There is never the level of accuracy that you need for building a staircase in a defined and confined space. The architect has the basic idea on the plan, but my task is to convert the concept to reality, in conjunction with the customer's ideas and preferences.
A photo of part of the architects' building plan.
The concept. 
These stairs would start in the hallway with treads 1 & 2 leading to a set of winders (Winding treads go around a corner, radiating out from the corner newel posts, making them wedge shaped). Treads 3,4 & 5 would be winders taking the stairs around a 90 degree turn. Treads 6 and 7 would be straight, linking this first set of winders to a second set of winders. Winding treads 8, 9 & 10 would then take us through another 90 degree turn, with treads 7 and 8 taking us through an opening in the wall into the kitchen/dining room. At this point the second set of winders would connect to a long flight consisting of treads 11 through to 20 (where tread 20 is the top floor level). A compact laundry would be built  under the long flight, concealed behind doors, and a wall built above alongside the long flight. Thus there was no connection between the stairs and the kitchen/dining/laundry area. The whole staircase is therefore U-shaped, with one leg longer than the other. It would also be a challenge to build... and I love these kind of challenges.
The top and bottom floor plans in the pics above give further info about the proposed layout.

The stairs were to be built using Jarrah, using as much of the original materials as possible. As was the norm in Western Australia for over 150 years, all the construction timbers in the house were jarrah, with a little bit of Karri. Modern carpenters & builders do not like using old jarrah. They love treated pine and LVL as it is light, easy to work, consistent in dimensions, and nail guns offer little resistance. So while the original roof timbers were removed to make room for the second storey, they were not re-used. Treated (CCA) pine was used for wall and roof framing upstairs. The old jarrah rafters and other roof timbers, which had been seasoning in the original roof for over 80 years, would be used where possible for building the staircase and for other joinery tasks around the house. The old house being recycled into the new parts of the house. Nice.
Sections of the rafters (4"x2") and ridge pieces (7"x1") docked oversize ready to be dressed.
The 4"x2" rafters would be docked, dressed, glued up and machined to size to make the stair treads. Any wider boards,  like hanger beams, would be used to make riser boards. Great to be recycling the removed original roof timbers back into the house as part of the staircase.

Planning the staircase build.
Walls were being rearranged, but there was enough detail available to take some initial measurements.

1. The overall TOTAL RISE has to be established. That is, the total height of the staircase. The vertical distance from the lower floor level and the top floor level. This was measured as 3650mm. Divide this by 20 treads, and you get 182.5mm. This is known as the RISE. This will be the measurement from the top of every tread to the top of the next tread. At many times during the building of the stairs, it will be helpful to have a Riser Story Stick - a straight narrow stick long enough on which to accurately mark off and number the position of every tread along it's height. A very handy tool!

2. The GOING has to be established. The Going is the distance from the face of one riser to the face of the next. Add all these together and you have the Total Going. By measuring the space available, we want to see that the total distance divided by number of treads will fit into the space within certain geometric parameters. Somebody once worked out that it takes twice as much energy to step up than it does to step forward, and this is used in establishing the relationship between the rise and the going.
Under the Building Code of Australia, staircases are required to comply with the parameters and formula in the table below. Working all this out is more complex when there are winders, but I calculated that the Going on the straight treads would be 265mm. This fits within the Code. If it didn't fit the formula range, then the Going or the number of treads (the Rise) would need to be changed until the formula complies. Adding a 15mm nosing to each tread, the stair tread depth (front to back) on the straight treads would be 280mm.

The Building Code of Australia says:

Riser (R)Going (G)        Slope relationship
Stairs (other than spiral)190115355240          700550

3. As accurately as possible, I transferred the measurements of the space available onto a  2.4 x 1.2m (8'x4') sheet of MDF, to create a full scale drawing (birds eye view) of the bast of the stairs. The treads, nosings, newel post and stringer dimensions, etc, would all be drawn onto this sheet, to ensure that it all fits. By doing this very accurately, this drawing could be used in order to measure and cut component parts as the build was taking place. An important reference item, this drawing would be, throughout the build.
One of the drawing boards, planning the winder and newel post positions.
4. Another sheet of MDF was used as a drawing board to do a full scale drawing (side view) of the top section of the long straight flight. This would be used to resolve the matter of the top of the stairs and the way they would connect to the top floor joists and or the wall. Using a full scale drawing would allow the planning and construction matters to be resolved and the components to be cut ready for installation. The final top tread's nose position also needed  to be resolved, to ensure the staircase would not terminate too close to the bathroom wall/door on the top floor. Sorry, I don't have a good pic of this drawing.
Not the accurate drawing... this one I did roughly on the wall! Resolving the top dimensions... 
The top tread would be made 130mm wide, as this matches the width of the jarrah floorboards to be used on the top floor. The rough wall sketch above was part of my thinking in pictures. I often do that... The big drawing was where I planned the way the top of the bight flight would be supported and connected. Sorry, no pic.

5. Another drawing! Yes, another full scale drawing was done on another sheet of MDF, showing the relationship of the three lower newel posts to the wall through which the staircase would pass, and where the treads would come in relation to the two short stringers supporting treads 6, 7 & the nose of 8. This was all going to be very tricky, so careful planning would be required. A full scale drawing is sometimes the only way to figure this out and create components with housings and tenons which will fit together perfectly.
You can't beat an accurate full scale drawing to work things out.
With all that planning, involving lots of mathematics, drawing, head scratching, and general cogitating there shouldn't be anything which could get in the way of it all coming together perfectly, should there?

Interestingly, step 5 would not be able to happen until a whole lot of other building work took place first - including the hole being cut in the wall through which the staircase would pass. Only then would those critical measurements be checked and confirmed. Like many of these older houses, things are not normally square, plumb or level. Oh well, that's all part of the fun with these gigs...

OK. Time to stop talking and start building!  The first task would be to build and install the long top flight.

The build begins!
The stringers for the long top flight would have to be bought new, as there was none available or suitable in the salvage yards I'd checked out. I dug through the limited pile of pre-dressed 10"x 2" jarrah sticks at the timber yard, and fortunately was able to find two which were long enough and straight enough. The longest one of these was 4.5m (15 ft) long - only just long enough for the outer stringer. Gee they were heavy!
Serious money in these two boards. Now I'm committed!
With the sticks loaded on the ute, I drove straight to someone else's workshop with the machinery big enough for me to flatten, straighten and thickness the big stringers to the required dimensions. They wouldn't fit in my little workshop or over my 6" buzzer! It was also a two people job. Once the basic machining was done, the sticks were loaded back onto the ute and I took them home to start setting out the housings for the treads and risers.
The building of the staircase had begun...