Final answer:
The minimum horizontal overlap for building paper should be 2 inches to create an effective moisture barrier, offering protection against environmental elements.
Step-by-step explanation:
The minimum horizontal overlap for building paper is typically recommended to be 2 inches. This overlap ensures that moisture is properly kept out, providing an effective water-resistant barrier. The building paper's horizontal overlap is essential for shielding the structure from environmental elements such as rain, which could otherwise seep through the seams and cause damage. When working with building paper, always follow the manufacturer's guidelines and local building codes, which may vary slightly in their recommendations but generally adhere to this standard minimum overlap.