what software are you using? if you use altium designer, after routing finished, place polygon(s) then you can change prefered clearance to whatever you want and rebuild your polygon(s).
1.Design
2.Rules....
3.PCB Rules and Constraints Editor
4.Design Rules
5.Electrical
6.Clearance
7.click Right
8.New Clearance
9.You Can Control
9.1Full Quency
InPolygon
9.2Full Quency
IsTrack and IsPad and IsVia
9.3Different Nets Only
30 mil or 50 mil or 10 mil
10.you can select many size Clearance.