Abstract: Interference factors for the mean pressure coefficient of a whole roof, the 1st modal generalized force and the unfavorable peak pressure coefficient are proposed to respectively evaluate the interference effects on the mean wind loads, fluctuating wind loads of a whole roof and local peak pressure coefficients. Pressure measurements of a flat roof surrounded by a similar building in a wind tunnel are conducted to examine the effects of the arrangement and the wind direction on interference factors for the mean pressure coefficient, the 1st modal generalized force and the unfavorable peak pressure coefficient. The results show that: the distribution of interference factors for the mean pressure coefficient of a whole roof is similar to that for the 1st modal generalized force; the shielding induces reduction interference effects when the interfering building is in front of the interfered building; amplification interference effects are significant when the interfering building is parallel to the interfered building perpendicular to the wind direction; the interference scope at oblique wind directions is bigger than that at the wind direction of 0#x000b0;; the interference effect is significant on the unfavorable peak pressure coefficient in the roof corner, but it is very small in the center zone of the roof.