Birds eye view of spraying polyurethane foam
This is what it looks like from a polyurethane foam applicators perspective when spraying foam.
Polyurethane foam should be sprayed at 1″ lifts for best results but never less than 1/2″.
How do can you tell if you are spray a 1″ lift? while it is true that you cannot see a 1″ lift you can hear it. That’s correct you listen for the tone. There is a sound it makes when you are spraying 1″. Once you hear the one by trial and error you will be able to lock it in to your brain. You will learn both the sound and the rhythm required to spray consistent foam roofs.