Maintenance Costs of Flat Roofs: Fid-Bau Portal

Maintenance Costs of Flat Roofs

R. Holmes / H. E. Marvin / W. B. Banks / M. E. Kroll / P. L. Newman

This paper describes two different but complementary studies of flat roof maintenance costs. The first study compares 360 heavyweight asphalt flat roofs with 245 traditional pitched tiled roofs on otherwise identical two-story semi-detached houses. The incidence of all repairs from age 13 to 29 years was obtained, with good estimates of costs from age 21 to 29 years. Maintenance costs depended on age and repair policy, and in the first 30 years of life the flat roofs probably cost about four times as much to maintain as the pitched roofs. Total capital and maintenance costs during a 60 year life are compared under varying assumptions about future inflation, interest rates and maintenance needs. For the flat roofs the total maintenance cost may be between 20 and 40 per cent of the total capital cost. The total cost-in-use is likely to be at least 50 per cent higher for the flat than for the pitched roofs. The second study compares the maintenance costs of 21 lightweight and 37 heavyweight flat roofs on university and school buildings. Roof areas are large, ages are mostly between 5 and 35 years, and designs are varied. Maintenance costs per roof generally increased with age but did not necessarily increase with roof area. The lightweight roofs were consistently more expensive to maintain than the heavyweight roofs.