I'm getting close to letting a contract to build the new shop, some builders choose to use  8' spacing on the post and trusses with the 2*4 purlins on their edge and others choose to put post on 8' centers with a truss and run a 2*10 or 12 on the outside and inside of the post and set a truss in bewteen the post on top of the 2* 10's or 12's ending up with trusses on 4' centers and then putting the purlins flat,,,I just wondered what opinons you guys had on one method or the other, we will most likely have 1/2" insulation board under the roof panels.

Also, how far north, "as far as snow load in concerned" is the 4' truss and flat purlin considered acceptable?.....thanks.....John