Frequently Asked Questions - Application

Roof slope is generally expressed in the form of vertical rise:horizontal run.  As an example, a roof could rise 5 inches for each 12 inches of horizontal distance.  This would be a roof with a slope of 5:12.  Roof slope is important because the slope dictates how the roof is applied.  The standard application practices detailed in the PABCO® Directions For Application are intended for roofs with a slope between 4:12 and 20:12.  Special application practices (also found in the PABCO® Directions For Application) are used if the slope is lower or steeper.

Do not use PABCO® shingles if the slope is less than 2:12.

See the PABCO® Directions For Application for additional details and related information.

What does roof slope mean and why is it important?

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® Directions For Application for additional details and related information.

Can I use PABCO® shingles on a low sloped roof?

Visit our Library page to view all out documents, or go to the Directions for Application section to get our product specific directions for application.