What is general contractorin construction?

A CMAR is hired during design, gives preconstruction pricing input, and then converts to a guaranteed maximum price (GMP) and holds the trade contracts, so during construction it looks and acts much like a GC. The practical differences are procurement and openness: a GC is usually selected on a lump sum bid against finished drawings, while a CMAR is selected on qualifications and fee, with open-book costs and savings typically returned to the owner. From an estimator's seat, GC bid work rewards aggressive buyout, while CMAR work rewards accurate early budgets.

Many commercial GCs self-perform a few trades where they own crews and equipment, most commonly concrete, demolition, rough carpentry, and general labor, and subcontract everything else. Others are pure brokers and subcontract 100 percent of the field work. On bid day the estimator makes that call trade by trade, comparing a self-perform estimate built from production rates against incoming sub quotes.

On a lump sum job the GC earns its fee plus whatever it saves in buyout, when subcontracts are bought below the numbers carried in the estimate, minus anything it loses to scope gaps or general conditions overruns. Fees on competitively bid commercial work are typically thin, often low single digits as a percentage of cost, so a few months of schedule slip on the superintendent and trailer line can erase the planned profit. That is why GC estimators obsess over schedule duration as much as quantities.