Quality Construction of Suspended Floors

Quality Construction of Suspended Floors

Posted By: Nyumba Imara Blog on 7th of November 2013

Building suspended floors that are acceptably flat and level is one of the many challenges that contractors may have to face in the course of a project construction. Whether supported by steel beams or a cast-in-place concrete frame every elevated floor deflects or sags slightly under its own weight. Structural drawings generally require that individual floor framing members have a slight camber, or hump in their profile prior to construction so as when cambered floor framing members are allowed to deflect they ideally will move to a level position. When everything works right, the floor’s finished surface will then perfectly complement structural deflection. Forms and shoring should be designed to allow safe, easy removal, while protecting the structure from excessive deflections at early stages. However buildings come in many shapes and sizes and as the available materials and floor framing are assembled together unique combinations are created thus the resulting floor systems do not always deflect to the engineer’s expectations. That's why the successful contractor must remain flexible and be ready to respond to jobsite developments. Success depends on two things—an effective preconstruction planning program and the ability to identify and adjust to unexpected conditions. Monitoring the Construction The goal in constructing any project is to meet and if possible exceed the requirements of the specifications. When evaluating construction of floors, the following standards, depending on the structural system should apply; Structural steel must be properly erected Steel connections must conform to the contract document requirements Concrete reinforcement must be placed and maintained in the proper location Concrete mix design, strength, and slump must conform to the specification Finished floor surfaces must meet the specified tolerances for levelness and flatness. The following are essential elements to be put in place so as to achieve a quality suspended floor; Preconstruction planning and meetings to minimize potential problems Gathering information during construction to allow evaluation of the work Responding to unexpected results by adjusting the design or construction Confirming that the adjustments are successful. Controlling quality Controlling the elevation of the supporting platform requires that engineering controls be established. The monitoring program for a structural steel frame provides key information about critical components such as base plate, column splice, and beam-to-column connection elevations, along with deflection of typical framing members. On a cast-in-place concrete frame, the contractor should select forming and shoring systems. Forms and shoring should be designed to allow safe, easy removal, while protecting the structure from excessive deflection at early stages. Evaluating concrete mix designs, delivery systems, and finishing techniques provides an opportunity to achieve the quality standards. Each decision will impact the flatness and levelness of the finished floor. Concrete mixes must develop adequate strength while providing good consolidation, consistent set time, and workability. The workers involved on the project must be capable of producing work that conforms to the quality standards. Concrete finishing techniques must produce the desired results. The pre-construction meeting is a good opportunity to address the team's plan for coping with isolated locations where actual deflection of the floor might be different from what is expected. Discussing job site controls for structural steel, form-work, reinforcing steel, concrete, and finished surface profiles will help ensure that backup systems are ready. Changes and substitutions in materials or admixtures should not be made without notifying and obtaining approval by the rest of the design/construction team.