In general, people who understand the strength and function of beams would be reluctant to introduce openings of any significant size without making a special study and providing strong compensating measures. Answers to questions that would be asked are provided in recent experimental research done at the Porland Cement Association Laboratories. The effects of openings in beams of commonly used floor systems are now well defined. Also, measures that must be taken when openings are included in beam design have been determined. Placement of openings in the webs offers advantages to contractors: they can accommodate the requirements of mechanical subcontractors and possibly reduce the bid prices they receive from them; openings created in beams during construction provide them with insurance against subcontractors who might otherwise cut unauthorized holes in the webs that would jeopardize the strength of the structure. Advantages to the designer and owner include improved versatility in the design which can contribute to lower costs. Openings can be produced in beams by providing blockouts, made of lumber if necessary, in the forms at the time of casting. However, they can usually be formed more conveniently by welding job-make polystyrene foam blocks into the web form. Such block of foam can be knocked out of the concrete without great difficulty after the forms are stripped, although removing the blockout does consume a measurable amount of time. The time can be reduced by using a patented polystyrene foam shape that is commercially available which is faster to remove. Openings can be sawed or drilled into hardened concrete if necessary but this costs quite a bit more.