PABCO® shingles can be applied on slopes as low as 2:12.
For slopes between 2:12 and 4:12, specific low-slope application practices are needed. For slopes between 2:12 and 4:12, the building code calls for covering the deck with an approved underlayment applied with an overlap 1” greater than half the width of the sheet.
As an example, the most common sheet width is 36”. For a 36” sheet the overlap is 19” (half of 36”, plus 1”). In most areas, the building code allows one layer of self-adhering polymer modified bitumen sheet which complies with ASTM D1970. PABCO® recommends this self-adhering sheet wherever this is allowed by code. You should confirm that this is allowed in your area.
The double layer of underlayment complies with code but the self-adhering sheet provides a greater margin for safety. See the PABCO® Installation Instructions for additional details and related information.