INTRODUCTION
    Many new homes have high entrance ways and other areas that require really tall ladders or a SCAFFOLD.  Recently, I decided to paint and add some crown molding to areas of my home that have  high ceilings. I don't like working from ladders, and I generally work alone,  so I  researched renting scaffolds.  After looking at rental fees, I decided to build my own out of easy to get lumber.  I used the scaffold  to paint walls that are 19 feet 8 inches high, and installed  crown molding with only a little help from my wife. It has a platform 12 feet high, and a 4 foot high safety railing around the top.
    The scaffold described here was easy to build, under $100 in parts,  but was actually cheaper, because I can use most of the lumber  for other projects, when I no longer need a scaffold. I made it for residential temporary use, but it could be reinforced with gussets, bolts instead of screws, and/or thicker wood to lengthen its life. This guide is only intended to show you how I did it. If you decide to build one yourself, you assume all responsibility and liability for its design, construction, use, and anything else.
CONSTRUCTION
Material List
Quantity    Size    Length
4    2x4    16'    legs (no cuts needed, but pick out carefully)
3    2x4    8'    platform support (cut to give (2) 66" and (2) 32" pieces)
16  1x3    8'    cross braces (no cuts)
3    2x3    8'    for stairs (cut to make (9) 32" pieces)
2    2x3    8'    for railing (cut to give (2)  66" and (2) 30" pieces)
1    5/8" plywood, approx 32.75x62.75 platform (thicker could be used)
4    felt-type self stick  floor sliders/protectors for bottom of  4 2x4's legs (for wood floors)
    1-5/8" sheet rock type screws for wood
    2-1/2" deck screws for wood

    This scaffold could probably be built from the picture alone, but I documented my efforts to help myself the next time.    There is a minimum of cutting and waste.  The three 2x3's for stairs, each require two cuts to give three (just a saw cut shy of)  32" pieces,  for a total of 9 steps. The steps are spaced one foot apart, and end one foot below the platform. This leaves a gap near the bottom that requires the use of  a stool, making the scaffold less inviting to little climbers.
    I  put self-stick heavy-duty furniture-type felt protectors on the bottom of the four 16'  2x4 legs to protect my wood floors and make moving the finished scaffold easy. I would probably leave them off for a rug or tile floor. I laid two legs flat on the floor, parallel,  32" apart. I marked a point 4' down from what would be the top of each. Starting 1' below the 4' marks, I made nine more marks on each, all 1' apart,  for the stairs. A 32" 2x3 stair joins the legs at each of the nine marks (but not at the first 4' mark).  I predrilled two holes on each side of the 2x3 steps, and using a total of  (4) 2.5" deck screws per step, screwed them to the legs to make a ladder. I did sink these screws in at least 1/4", to get more bite into the legs. 3" screws might have been better, but would have stuck out a bit.  Similarly, I added a 30" 2x3 for a  railing centered at the very top of the two legs.  I flipped over the ladder, and screwed the 32" 2x4 platform support, at the 4' mark  using (4) 2.5" screws.
    After turning and balancing the ladder on its side, I screwed first one 2x4 66" platform support perpendicular to the ladder, on  the front at the  4' mark, with just one screw temporarily, but I predrilled the support for a second screw . I did not snug the screw,  to allow the long platform supports to swing, without coming loose. I swung the long support so it was parallel to the ladder.  I turned the ladder and put another long platform support on the other side, the same way.
    I raised the ladder (with the supports hanging down parallel to the ladder), and rested it high on a wall.   Using a step ladder, and a partner to  hold up one of the two remaining 16 footer legs, I swung out the long platform support from the ladder, and screwed it to this leg, again four feet down from the top, two screws, and then another screw for the first side that was swinging.  Similarly, I screwed the last leg to the other long platform support. Then I added the last short platform support, using two screws on each end, predrilling only the support. Note that the long supports are on the outside of the legs, while the short supports are on the inside of the legs. At this point I had  a very wobbly frame.
    Using (8) eight-foot long 1x3's, I added  one cross brace "X", on each of the four sides of the scaffold,  starting about inch up from the bottom of each leg. The 1x3's are perfect because I simply bent  them around each other at their intersection. I used two 1-5/8 sheetrock type screws at each end, and one 1-1/2" screws in the intersection, all predrilled  to prevent splitting. Then using another eight 1x3's, I added a second row of  X's.   For the sides, you can cut the 1x3's or overlap them, since the X's will be longer than required, unlike the front and back. At the end of this step, the scaffold is rock solid, with little or no wobble.  
    I then measured the final platform width and length, and cut the piece of plywood to fit snugly. I screwed it down using sheetrock screws. I double checked all screws on the entire scaffold for tightness.