Will's books

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Monday, May 28, 2012

The history and tools of production roof cutting

*** If you like this post you will absolutely love the chapter entitled "Roof Cutters - A flash in time" in Will Holladay's new book From the Top Plates Up. That chapter provides the most detailed look at the history of production roof cutting ever written.***
   Production roof rafter cutting has a very interesting history that most rough carpenters find enthralling.  I was lucky to have lived and worked through it and still remember most of it like it was yesterday.  Roof framing has always been a joy. 
   Production framing in general was started by the US military during WW2.  So many housing units were needed in record time that the assembly line method developed in car and aircraft production industry was applied to building (see this amazing video).  After the war, home contractors used these same methodologies and processes to handle the immense pent up demand for civilian housing that had been caused by the population shift to California and other parts of the West Coast for wartime production.  Prior to these post WW2 days production home building was virtually unheard of as all houses were hand built by a the same crew of men from start to finish, one at a time. When the post WW2 building boom hit the Los Angeles in the early 1950's, this age-old house building method was discarded and carpenters became specialized in just one production assembly task.  Contractors began throwing up wholes tracts of houses in record time using the moving assembly line method.  It seemed as if one day a field stood empty and the next day it was filled with houses.  Tract carpenters were paid by the piece - a price per square foot to do a certain task.  For example: 5 cents a square foot to snap, plate and detail; 8 cents to stand walls; 4 cents a square foot to cut rafters; etc (mid-1970's prices). With pay for performance as the incentive, tract carpenters thought up new techniques, found short-cuts, modified existing tools to do something more efficiently, and invented new tools.  From these "piece work" days came most of the specialty framing tools we use today (large diameter portable circular saws, dado saws, bolt markers, layout sticks, triangular rafter squares, framing hammers, saw hangers, etc).  "Necessity is the mother of invention" as they say.
   The production roof cutting of rafters reached its peak in the late 1960's and early 1970's and died almost overnight when roof trusses gained prominence in the late 1970's.  So nowadays, for the most part, true production rafter roof cutting is only a memory and these methods are rarely seen except on the occasional stick framed roof done by the custom builder.
   Although gang-marking racked lumber dates back to the Middle Ages, rafters were still laid flat and cut one at a time up until the WW2 when the production gang-cutting of rafters began using the Delta radial arm saw.  This chore was moved from a fixed saw shack job to a job-site task in the early 1950s when the Skil 117 "Groover" was adapted to gang-cut the birdsmouth notch.  The "Groover" was a powerful (18-20amp) 2-in.wide portable wormdrive dado-saw manufactured by Skil Power Tools from the late 1940's to the mid-late 1960's (est).  It was based on the Skil 107 (10-in.wormdrive circular saw) and was originally designed to cut a square notch in beams or joists to run electrical wiring (back in the days of knob and tube type electrical wiring).  With a little modification to the blade guard, it was able to tilt sideways, making the Skil 117 the perfect tool for gang-cutting birdsmouth notches on racked lumber.

Skil 117 "Groover" with 2" wide 7.25" diameter dado set

   By the mid-late 1960s saw shops in the Los Angeles area began to modify the Skil 107 to carry a 3.5-in. dado set in order to fulfill the desires of various framing contractors who wanted a larger birdsmouth notch than the Groover could easily produce.  Nate Fletcher, formerly of Nate's Saw Shop (Anaheim, CA) was one of the principal innovators behind this and other saw modifications.  Nate modified close to 200 Skil 107s during the Los Angeles building boom days.

Skil 107 adapted with 3.5" wide 6" diameter dado set

   When the supply of 107s dwindled (these big barrel saws were never very popular on the job as they weighed over 30 lbs), several saw shops around CA began modifying the newer Skil 77 and 87 wormdrive models.  Pairis Products (Phelan, CA) made a kit for the 77, while Furber Saw (Martinez, CA) made a kit for the 87.  Both kits were available up until the early 1990s.
   Because the dado saw required quite an investment, an optional method to gang-cut birdsmouth notches arrived on scene in the early 1960s in the form of the swing-table saw base.  It was inexpensive and simple, and favored by most everyone other than the dedicated roof cutter.  A swing-table saw base installed on a standard circular saw allowed it to swing well past 45 degrees and get the shallow angle required for the seat-cut.  Both Pairis Products and Big Foot Saw (Henderson, NV) currently make models for various saws.

Swing-table for Skil 127
   While the dado-saw or a saw with a swing-table made quick work of gang-cutting the rafter birdsmouth notches, a fast method was needed to gang-cut the ridge-cuts.  The largest portable saw circular saw in the early 1960s was the 20 amp Skil 127 (12-in. wormdrive circular saw), which could gang-cut 2x4 rafters racked on edge (the common rafter size back in those days) but fell short of reaching through a rack of 2x6s.  The method developed for larger material was to use the 127 (or even a standard 77) to make a starter ridge-cut pass and then finish off the unreached part of the cut with a sidewinder blade mounted on a Skil 77.  While inherently dangerous because the blade was outside the guard, the sidewinder in the right hands proved to be a very efficient tool for finishing off plumb-cuts.  OSHA eventually pressured the blade out of production in the mid 1990s.

Sidewinder blades for Skil 77 (red paint to repel rust)
   In the mid 1960s Nate Fletcher began modifying the Skil 127 with 18-in.or 20-in.blades of the big Delta radial arm saws, which allowed roof cutters to gang-cut the ridge-cut in one pass.  The 20-in. blade could cut through 2x8 racked on edge up to a maximum pitch of about 5/12.  In the late 1970s Makita introduced the 16-in. beam saw (model 5402).  It was able to cut 2x6s racked on edge up to a maximum of 5/12 but lacked the power for long, continuous, rip-style cutting, as it was designed more as a beam cutoff saw.
   In the late 1980s, the Linear Link saw (Muskegon Tools, North Muskegon, MI) arrived on scene with a self-oiling 14-in. chainsaw bar attached to a Skil 77 motor body.  Because it could be tilted sideways, some carpenters used it to make the ridge-cut on racked rafter material but it was very underpowered for these type of cuts and not nearly as precise as the circular saw.  Another similar device, the Prazi Beam Cutter (Prazi USA, Plymouth, MA) came along in the mid 1990s.  It had the same drawbacks as the competition and worse yet, no provision was made for chain self-oiling.  In 1997, Big Foot Saw made available the "Headcutter", an adjustable saw table that attaches to a gas-powered chainsaw.  It instantly became the best option available (and still is) for gang-cutting the plumb-cuts on common rafters.  It combines a powerful gas motor, a self-oiling chain system, and a large saw foot for making accurate cuts.  Fitted with a chisel-tooth ripping chain, it is hard to tell the cut made using the "Headcutter" from one made with a circular saw (the "Headcutter" also works well for precutting bundled I-joists to length or the cutting of structural insulated panels).

Big Foot Saw "Headcutter" chainsaw base
   The Europeans have been gang-cutting timber frame beams since the late 1950s and early 1960s.  Mafell AG (Germany) began manufacturing a 16-in. diameter saw in the early 1950s and added a vertical cutting electric chainsaw in the early 1960s.  Today, Mafell North America (Williamsville, NY) offers many variations to these same tools, including a 25-in.circular saw (portable?? -145 lbs) and a 4.5-in. dado-saw called a skew-notch and tenon cutter.  These tools are very pricey and geared more for a factory environment versus something a common carpenter might have in his/her tool box.  I did try the single phase Mafell dado to gang-cut rafters in 2001 and was disappointed.  I found it lacking in power and the planer style blade cut poorly.  I can not comment on their recent 3 phase model but having 220 will certainly help in the power aspect..

Adapted from the JLC version of "A Roof Cutter's Secrets". Copyrighted 2002 by Will Holladay.


One "very cool" unique stairway - Part 1: design

One "very cool" unique stairway

   While doing a skills training course overseas, a local businessman approached me about designing and building a staircase for his mountainside office retreat.  His only requirement was that it must be an original "never seen before" design.  How could I pass up a chance like that - of course I accepted.
  The building being constructed as his mountainside office was a two-story concrete block hexagon with approx 15' sides (everything was in metric, of course).  The front side of the hexagon faced out over the hillside and took in an incredible 270 degree view.  The lower level had a set of French double doors that opened onto to a large patio with a deck that overhung a steep fall-off grade.  Located inside along the back wall (opposite the doorway and patio) was a long, thin, single story bathroom with a flat shelf type ceiling when viewed from the loft above.  The upstairs level was nothing more than a gently curving loft style floor having a small "standing room only" balcony extending out a set of French double doors over the patio below.  The loft covered slightly more than half of the lower floor's footprint and was located just under 9' above the first floor.  The floor joists defining the loft hung off the front wall (or the wall with the double patio doors) and cantilevered over a steel beam run down the middle of the building from side to side.   There were no interior walls, no stairs yet (of course) and the building was open two stories to the roof rafters.  It had a very nice airy feeling inside and a view from just about any position inside except the bathroom.  The downstairs was to have a centrally located pool table with a small entertainment/living room area off to one side and the stairs set off to the other side.  The upstairs loft was the office.  The placement of the bathroom door on the back wall limited the placement of the stairs so there was only about 8' of horizontal space available to ascend 9' vertically.  I could definitely see the challenge of building a normal staircase within the space available given the need to keep the center clear for the pool table.  The architect had figured only  a ladder-type or spiral staircase would work.  Neither was acceptable to the owner
  After a little brainstorming, I suggested we convert the dead space over the bathroom to a separate library space with built-in shelves and connect it to the office loft by means of a centrally located front to back "step-up" bridge (versus a bridge built to be flush with the loft floor).  From the loft end of this bridge, the staircase would descend towards the side wall which was opposite the fireplace (where the architect had originally planned his ladder or spiral design staircase) and then hook around to the right to terminate at the bathroom door (door would swing in).  The staircase would be shaped like a reverse question mark (?).  In keeping with the radius type theme of the loft, the bridge would have a gentle hourglass shape and the stairs would follow/match the curving front edge of the loft until near the outside wall were they would reverse and begin an ever tightening nautilus type curve to the the right.

Design sketch

  Not only would the stairs be irregularly curving in structure but I also designed the treads and risers themselves to be curved and progressively changing from a gentle curve with a long radius at the bridge to a much tighter curve with a short radius at the very bottom step.  Compounding this, I would support more than half the stairs by straight-run stringers to keep the the center of the lower floor area free of obstacles for the pool table.  Having the bridge as a "step-up" design helped increase the headroom below the straight run section of the stairs until they were much closer to the side wall  The first 7 risers in the lightly wound bottom section located against the buildings exterior walls would be built using a combination of short 2x4 walls and 2x12/2x4 riser assemblies as shown on pgs 276-277 in the 2002 version of "A Roof Cutter's Secrets" (RCS).  The more gently curving upper 9 treads would be supported by three regular 2x12 stringers.  A half arch would serve as the transition from wall style stair construction to the notched stringer style construction.  I would frame the structure using straight lines for the treads and risers, while a cabinet shop would build the finished treads and risers and apply them as an overlay.  The curved lower support walls, the arch and the stringer assembly would be finished with plaster to create a contrast to show off the magnificent tropical hardwood top surface.

Continued in Part 2: layout and construction

Copyright 2008 by Will Holladay

One "very cool" unique stairway - Part 2: layout and construction

  Since the stairs didn't follow any singular geometric shape, I would need to freehand draw the finished design on the floor in its exact position where directly above would be located the staircase.  I began by calculating the number of risers that would produce a +/-7" riser height, then I drew a "shadow" outline of the stairway on the ground and marked out a line-of-travel (12" in from the inside edge of the staircase).  Following this line, I marked layout of my desired treads (11") starting at the side of the bathroom door.  The last tread on this line located where to set the near edge of the bridge.  I bent a 20' piece of 1/2" plastic PVC pipe to draw the curved edges of the bridge and the first tread at the bottom.  Then, using the geometric solution shown on RCS pgs 285-6 I found the radius of the first curved tread at the bottom and the radius at the last tread at the bridge.  With those two numbers in hand, I divided their difference by the total number of stair treads to find the amount needed to progressively enlarge the radius of each subsequently higher tread to make a smooth little noticed transition from the tight curve at the first step to the gentle curve at the bridge edge.  Using these constantly changing radii, I drew in the intermediate treads.  When I was pleased with the stairway floor design drawing, I superimposed layout lines for the actual sides of the framing substructure which would be inset 2" from the tread width.  After 3/4" plaster was installed it would leave about 1" reveal from the sides of the finished treads.
  Next, since the curved tread lines on the floor drawing signified the nose of the finished treads I placed a parallel curving line "uphill" 2" from each of the tread nosing lines.  This setback dimension would allow space (with play) for the curved 3/4" finished risers and a 1" nosing reveal.  Now, because I would be building the framed tread/riser substructure using straight lines (only the finished risers would be curved) I snapped straight lines from side-to-side where the curved 2" nose setback line intercepted the 2" inset framing lines along the side of the stair width.  These straight riser lines would be my actual guide for the riser part of the stair's substructure framing.  The finished tread overlay assemblies would butt against the straight riser sub framing at each level.

Stairway floor drawing
  For the straight run stringer section of the stairs I snapped three 2x stringers inside of that portion of the stairway which paralleled the gently curving loft edge from the bridge to the last 2x12 riser assembly supported by a little 2x4 wall.

Framing substructure sketch
  Satisfied with my now completed floor layout I sprayed all my penciled and snapped lines with aerosol varnish to protect them from foot traffic.
  I then used the floor drawing to make cardboard patterns of each finished tread and passed them along to the cabinet shop.  They would copy these patterns to fabricate the curved 3/4" thick treads/risers.

Cardboard patterns for fabricating finished treads
  Next, using the floor drawing I cut the curved bottom plates, the bottom section's 2x12/2x4 riser assembles, the finger joists interconnecting the riser assemblies, and all the plywood treads/risers.  I pre-assembled as much as possible.

Pre-cutting all the 3/4" plywood treads
  Then I faced the challenge of cutting the straight run stringers for the gentle curving section.  This was a bit difficult because none of the stringers would be uniform and there would be variations in tread width and riser angle at each step.  Only the riser height would be consistent.  Working off the floor drawing I laid out each stringer with the shortest tread length found along its run together with the given rise.  Then I backtracked and modified each tread for the actual tread dimension found on the floor drawing.  Angles for the riser-cuts where taken off the floor drawing using a protractor and the circular saw adjusted accordingly to make each riser-cut on the stringer.

Stringer layout technique
  Now with all the pieces cut, I began assembly.  The bridge framework went up first.  I placed two 6x6 hardwood beams to span the gap from the former bathroom ceiling (now a converted library floor) to the loft section.  I added several extra joists in the loft floor structure to handle the new loading.  The library end of the bridge flared out wide so I installed two jack beams to support the cantilevered 2x6 T&G decking (which would be added as the last step).
  I began stair assembly at the bottom working upward one step at a time, constantly checking with a level and laser to keep everything aligned perfectly with the floor drawing below.   I had a story pole tacked up on the adjoining wall so I could direct the laser horizontally at it and verify that I was staying exactly on each step's rise measurement.
Attaching the plates for the bottom 7 steps
Using the laser directed to the story pole at side of doorway



  When I had completed building the bottom 7 steps, I hung the stringers from the last 2x12 riser assembly to the bridge's nearside 6x6 beam.  I used the laser to position them so they matched exactly with the floor drawing below.  The stringers were cut to flush with the top of this beam (my standard stringer framing method as seen on pg 271 of RCS).  I used the same laser technique to positioned the plywood treads/risers side-to-side.
  Once the plywood treads/risers were fastened in place on the open stringers, I furred both outside stringers to the shape of the floor drawing below by placing nailing strips of varying thicknesses behind each riser.  The I overlaid the sides with 1/2" plywood sheathing to create the curved form.  The plywood reached back to the wall supported stair section and served as the basis for the transitional half arch.

Furring the outside stringers to match the floor drawing

Overlaying with 1/2" plywood to form the curved sides

The side plywood also served as the basis for the transitional arch

  The final part of framing these stairs was to install the 2x6 T&G decking on the bridge framework.  During application, I ran each board long at both ends and cut them all together using a jigsaw.  To transfer the curved hour glass bridge shape from the floor drawing to the top surface of the deck I used the laser shot upwards from the floor to mark outline points along the underside of the decking every 16" +/-.  At each of these "underside of deck" points I drilled a small pinhole up through to the top surface of the deck.  Then using the 20' piece of 1/2" plastic PVC pipe again, I bent it around nails that were partially driven into each of the pinhole locations and drew out the curve.

Cutting the bridge decking.  The left side near edge served as the last curved tread.
   After tile was laid on the lower floor, the cabinet shop installed the curved Mahogany treads/risers to finish up this true "one and only" staircase.
  Several years after I completed the job the owner did unfortunately modify the design slightly by fabricating special curving steel beams which allowed the removal of the structural 2x4 wall section at the bottom 7 risers.  This gave the staircase a more open look but the stairway did end up springy which my original method of construction had avoided.

Finished stairway

Finished bridge

Copyright 2008 by Will Holladay