In the WFCM, Mean Roof Height is defined as “the distance from the average grade to the average roof elevation.” See WFCM Figure 1.2.

The WFCM is limited to a Mean Roof Height (MRH) of 33′ or less, but the envelope method in ASCE 7-10 that is used in the WFCM has a limit of 60′.