New Hydraulic Elevator: Pit Depth Does Not Match the Certified Drawing
You are installing a new two-stop hydraulic elevator in a renovated two-story building. The certified layout calls for a 48-inch pit depth, a 12-inch-diameter jack hole 84 inches deep, and a PVC casing. After the pit is poured, your laser measurement shows 45 3/4 inches from the finished pit floor to the finished lower landing sill. The jack hole is 84 inches deep and appears plumb. The general contractor says the concrete is already at cure and proposes two field fixes: cut 2 1/4 inches off the top of the plunger, or set the jack on a 2-inch steel shim plate. The elevator permit has been issued based on the original drawing. The car sling, buffer, and cylinder are on site. The building owner wants the elevator running for a tenant move-in in 10 days.
1. Evaluate the two proposed field fixes. What must happen before any modification is accepted?
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Neither field fix should be accepted on the general contractor's authority. Cutting the plunger changes the manufacturer's designed stroke and the relationship between the plunger, cylinder, and buffer. A shim under the jack changes the jack elevation and may reduce the required buffer clearance, runby, or cylinder support. Both are alterations to the certified design, not installation adjustments. The first step is to verify the measurement: confirm the datum, check that the pit floor is the finished surface, and compare the actual dimension with the certified drawing and the manufacturer's installation manual. If the pit is truly short, the manufacturer's engineering department must evaluate options in writing. Possible acceptable solutions include lowering the pit, reducing travel or changing stop locations, using a different cylinder or jack assembly, or obtaining a code variance from the authority having jurisdiction. Any change to the approved drawing requires a revised permit submittal before work proceeds. The 10-day schedule does not justify an unapproved field modification.
2. What measurements and documents should be assembled for the manufacturer and the code official?
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Assemble a measurement package that lets the manufacturer and code official evaluate the actual condition without visiting the site. Include pit depth at each corner and at the center, lower landing sill elevation, pit floor elevation, jack hole depth and plumbness, cylinder location, and the distance from the pit floor to the underside of the car sling at the lower landing. Include the certified drawing, the manufacturer's installation manual, the permit, and the approved plan set. Identify the buffer type and required stroke, because pit depth is not just a round number; it must accommodate the buffer, the car sling, and the required clearances. Photograph the pit and jack hole with a tape or laser target in view. Send the package to the manufacturer for a written recommendation, then submit any resulting change to the code official for approval before ordering parts or modifying concrete. Keep the signed and sealed response in the job file, because the inspection will ask why the installed condition differs from the permitted drawing.