What is the total allowance for a ¼" double seam?

For a ¼" double seam, the total allowance is indeed ¾". This is derived from the nature of a double seam, which involves two overlapping pieces of sheet metal. Each seam requires a ¼" allowance for proper formation and strength.

When constructing a double seam, the first ¼" is used to connect the first layer of the metal to the second, and the second ¼" is used for the other layer. This results in a total of ¼" for each side, effectively doubling the allowance to ¾" when completed. The sum of the allowances for both sides of the seam is where the total of ¾" comes from.

Understanding the dimensions and methods of seams is vital in HVAC sheet metal work, as properly calculated allowances ensure the integrity and effectiveness of the seams in practical applications.