Flat roofing systems in Seattle cost $5 to $12 per square foot installed, depending on the membrane type and roof size. TPO, PVC, and modified bitumen are the three most common flat roofing materials in the Pacific Northwest, each offering distinct advantages for commercial buildings, multi-family properties, and modern residential designs with low-slope roof sections.
Drainage is the defining challenge of flat roofing in a city that receives 150+ days of rain per year. Every flat roof we install is engineered with proper slope (minimum 1/4 inch per foot), correctly sized internal drains or scuppers, and overflow provisions in case primary drains become blocked. Ponding water, where standing water remains on the roof 48 hours after rainfall, is the leading cause of premature flat roof failure. Our drainage engineering eliminates that risk.
