Commercial roofing requires more skill and properties to construct a roof that is durable and up to code. The installation process differs from residential in that it takes much longer and requires more people. The roofer installing a commercial roof must be knowledgeable about obstacles such as external piping, smoke stacks and airflow systems. The process of repairing a commercial roof is more complex than a residential one. A leak in a commercial roof may result in the entire roof needing replacement.