Did you know there is a EIFS minimum requirement for EPS Foam thickness?
You may be under the EIFS minimum requirement for EPS Foam thickness because of an industry shift from 1 1/2″ foam to a 1″ foam standard. With the rising cost of material we have found that many Synthetic Stucco contractors are pushing 1″ foam. In years past the norm was an 1 1/2″ of foam. The problem with using one inch foam is that the minimum requirement for the EPS Foam is 3/4″ which one inch would seem fine then, but after sanding the foam it is getting close to the 3/4″ in troubled areas that need a little extra sanding, but that is not the real problem. The problem is that in many cases the design calls for aesthetic reveals or v-grooves, which are cut into the foam with a hot knife. These aesthetic reveals are anywhere from a 1/2″ to 3/4″ deep when using one inch foam. If you use one inch foam you are limited on your design because you cannot use the aesthetic reveals. The use of aesthetic reveals are great for stopping points when applying the EIFS finish coat so the entire area does not have to be done at once. Also, the aesthetic reveals allow for easy and cheaper repairs if the Synthetic Stucco becomes damaged down the road. Exterior Insulation and Finish System needs to re-finished from coast-to-coast to look brand new, otherwise you will be looking at a patch in the middle of a huge wall. Aesthetic reveals can add to the beautiful design of Synthetic Stucco, help the applicator when applying the finish coat, save costs on repairs. The cost savings of using 1″ foam is not worth the disadvantages and usually these savings are not passed down to the customer. Another disadvantage of using the thinner foam is the r-value you are losing. Your EPS Foam will be a 1/3 thinner so you will be decreasing your r-value of the Exterior Insulation and Finish System by that much. You will still be virtually eliminating thermal bridging but for my buck I want to keep my r-value as high as possible. The technical term for what I have been calling ‘foam’ or ‘EPS Foam’ is expanded polystyrene (EPS).
There are places where you would use one inch Styrofoam. Window returns come to mind off the top of my head. Typically, the clearance around the window is much lower than the field wall. Door clearances have the same clearance issues. Also, one inch Styrofoam can be used in decorative trim applications