A roof mounting system for attaching at least one PV module (170, 172, 174) to a roof, the system comprising: (a.) a roof having a roof surface; (b.) a plurality of base mount assemblies, each of the plurality of base mount assemblies comprising: (i.) a base member having a first surface adjacent the roof surface and a second surface opposite the first surface, wherein an upstanding projection is connected to and extends away from the base member, the upstanding projection comprising a distal end having a distal end aperture; (ii.) a block member comprising a substantially horizontal portion and a vertical engaging portion, wherein the substantially horizontal portion has a borehole formed therethroughconfigured to receive the upstanding projection; (iii.) a tightening means inserted through said borehole and distal end aperture, the tightening means attaching the block member and base member to the roof, the tightening means having a long portion and a head portion; and (iv.) a sealing washer between the head portion and the upstanding projection distal end, the sealing washer comprising a steel disk contacting the head portion and a deformable part contacting the distal end thereby forming a waterproof seal; and (c.) at least one PV module (170, 172, 174) coupled to at least one of said plurality of base mount assemblies, the at least one PV module (170, 172, 174) having a mounting height; and (d.) a sliding member having a sliding groove mating with the vertical engaging portion to adjust the at least one PV module mounting height. (a.) a roof having a roof surface; (b.) a plurality of base mount assemblies, each of the plurality of base mount assemblies comprising: (i.) a base member having a first surface adjacent the roof surface and a second surface opposite the first surface, wherein an upstanding projection is connected to and extends away from the base member, the upstanding projection comprising a distal end having a distal end aperture; (ii.) a block member comprising a substantially horizontal portion and a vertical engaging portion, wherein the substantially horizontal portion has a borehole formed therethroughconfigured to receive the upstanding projection; (iii.) a tightening means inserted through said borehole and distal end aperture, the tightening means attaching the block member and base member to the roof, the tightening means having a long portion and a head portion; and (iv.) a sealing washer between the head portion and the upstanding projection distal end, the sealing washer comprising a steel disk contacting the head portion and a deformable part contacting the distal end thereby forming a waterproof seal; and (i.) a base member having a first surface adjacent the roof surface and a second surface opposite the first surface, wherein an upstanding projection is connected to and extends away from the base member, the upstanding projection comprising a distal end having a distal end aperture; (ii.) a block member comprising a substantially horizontal portion and a vertical engaging portion, wherein the substantially horizontal portion has a borehole formed therethroughconfigured to receive the upstanding projection; (iii.) a tightening means inserted through said borehole and distal end aperture, the tightening means attaching the block member and base member to the roof, the tightening means having a long portion and a head portion; and (iv.) a sealing washer between the head portion and the upstanding projection distal end, the sealing washer comprising a steel disk contacting the head portion and a deformable part contacting the distal end thereby forming a waterproof seal; and (c.) at least one PV module (170, 172, 174) coupled to at least one of said plurality of base mount assemblies, the at least one PV module (170, 172, 174) having a mounting height; and (d.) a sliding member having a sliding groove mating with the vertical engaging portion to adjust the at least one PV module mounting height.