How many columns must receive thickness testing when 200 columns are installed on a floor?

The correct answer aligns with the established guidelines for thickness testing in construction practices, particularly when dealing with fireproofing materials applied to columns. Typically, the industry standard dictates that when a certain quantity of elements, such as columns, is installed, a representative sample should undergo testing to ensure the application meets the required fire resistance standards.

For 200 columns, the specified sample size for thickness testing is often a percentage that provides a balance between ensuring quality control and not overburdening resources. In many instances, this percentage is set at 25%. Therefore, to determine how many columns need to be tested, calculating 25% of 200 results in 50 columns. This number of columns is sufficient for assessing the overall thickness applied while ensuring that the fireproofing application complies with safety regulations and specifications.

This principle of testing a smaller percentage from a larger group helps to maintain efficiency in building practices while ensuring safety standards are upheld throughout the installation process.