to assemble the secondary gutter assembly 30 comprising pans 64 to 70 and membrane 100 in place over beams 96 and 98 and joists 76 and 78 after ascertaining the location of the downspouts 148 and 150 to which the secondary gutter 30 is coupled the secondary gutter pans 66 and 70 with previously formed drop holes are placed over joists 76 and 78 so that the drop holes are aligned with downspouts 148 and 150 thereafter the remaining secondary gutter pans 64 and 68 are assembled in place referring to fig1 a 1b and fig8 gutter pans 66 and 70 are formed with end portions 218 adapted to telescope inside adjacent end portions 220 of respective pans 64 and 68 any suitable fasteners such as screws 222 received in holes 224 may be used to secure adjacent end portions 218 and 220 if desired rather than being secured together as shown pans 64 and 68 may be lapped or butted around pans 66 and 70 respectively to minimize the need for field cutting of the gutter pans no mastic is required on the joints between pans 64 and 66 and pans 68 and 70 since the flexible membrane 100 later to be installed provides the water tight gutter function gutter pans 66 and 68 are terminated a suitable distance from beams 96 and 98 while gutter pans 64 and 70 are similarly terminated a suitable spacing from parapet walls 18 and 20 to avoid any possibility of contact with these structural members in the course of expansion or contraction relative thereto after gutter pans 64 66 68 and 70 have been positioned on joists 76 and 78 and assembled relative to one another in the manner described above they.