From: Jeffrey Epstein <[email protected]> To: TOM MELNICK Subject: Date: Wed, 07 Mar 2012 00:02:20 +0000 >, ' Ergonomically and for safety reasons, stairs must have certain measurements so that people can comfortably use them. Building codes typically specify certain measurements so that the stairs are not too steep or narrow. American building codes specify the following parameters:MM • Minimum tread length, typically 9 inches (229 mm) excluding the nosing for private residences. Some building codes also specify a minimum riser height, often 5 inches (127 mm).[I] • Riser-Tread formula: Sometimes the stair parameters will be something like riser + tread equals 17-18 inches (432-457 mm);[i another formula is 2 times riser + tread equals 24.6 inches (625 mm), the length of a stride.M Thus a 7 inches (178 mm) rise and a 10.6 inches (269 mm) tread exactly meets this code. If only a 2 inches (51 mm) rise is used then a 20.6 inches (523 mm) tread is required. This is based on the principle that a low rise is more like walking up a gentle incline and so the natural swing of the leg will be longer. This makes low rise stairs very expensive in terms of the space consumed. Such low rise stairs were built into the Winchester Mystery House to accommodate the infirmities of the owner, Sarah Winchester, before the invention of the elevator. These stairways, called "Easy Risers" consist of five flights wrapped into a multi-turn arrangement with a total width equal to more than four times the individual flight width and a depth roughly equal to one flight's run plus this width. The flights have varying numbers of steps. • Slope: A value for the rise-to-tread ratio of 17/29 0.59 is considered optimal;[ 1 this corresponds to a pitch angle of about 30°. • Variance on riser height and tread depth between steps on the same flight should be very low. Building codes require variances no larger than 0.1875 inches (4.76 mm) between depth of adjacent treads or th