Flat roofs are a cost-effective option for both residential and commercial buildings. Typically, flat roofs cost less to install compared to pitched roofs due to their simpler design. For materials like EPDM rubber or PVC membrane, you can expect to pay between $5 to $8 per square foot. While the initial installation may be cheaper, keep in mind that flat roofs may require more maintenance over time due to drainage issues. Budgeting for periodic inspections and repairs is essential to avoid costly water damage.