Figure 6-18.—Layout of upper end of cutout stringer.thickness of a tread less the thickness of the finishflooring. The first is done if the stringer rests on a finishfloor, such as a concrete basement floor. The second isdone where the stringer rests on subflooring.Figure 6-19.—Kickplate for anchoring stairs to concrete.When you have shortened AD to AE, draw EFparallel to AB. This line represents the bottom horizontalanchor edge of the stringer. Then, proceed to lay off theremaining risers and treads to the unit rise and unitrun until you have laid off 15 risers and 15 treads.Figure 6-18 shows the layout at the upper end of thestringer. The line AB represents the top, the 15th tread.BC, drawn perpendicular to AB, represents the uppervertical anchor edge of the stringer. This edge buttsagainst the stairwell header.In a given run of stairs, be sure to make all the risersthe same height and treads the same width. An unequalriser, especially one that is too high, is dangerous.STAIRWAY CONSTRUCTIONFigure 6-20.—Finish stringer.We have been dealing with a common straight-flightstairway—meaning one which follows the samedirection throughout. When floor space is not extensiveenough to permit construction of a straight-flightstairway, a change stairway is installed-meaning onewhich changes direction one or more times. The mostcommon types of these are a 90° change and a 180°change. These are usually platform stairways,successive straight-flight lengths, connecting platformsat which the direction changes 90° or doubles back 180°.Such a stairway is laid out simply as a succession ofstraight-flight stairways.The stairs in a structure are broadly divided intoprincipal stairs and service stairs. Service stairs areporch, basement, and attic stairs. Some of these maybesimple cleat stairways; others may be open-riserstairways. An open-riser stairway has treads anchoredon cutout stringers or stair-block stringers, but no risers.The lower ends of the stringers on porch, basement, andother stairs anchored on concrete are fastened with akickplate (shown in fig. 6-19).When dealing with stairs, it is vitally important toremember the allowable head room. Head room isdefined as the minimum vertical clearance requiredfrom any tread on the stairway to any part of the ceilingstructure above the stairway. In most areas, the localbuilding codes specify a height of 6 feet 8 inches formain stairs, and 6 feet 4 inches for basement stairs.A principal stairway usually has a finishedappearance. Rough cutout stringers are concealed by6-14
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