Roofing Types & Info

Introduction & Rules of Thumb

Roofs, when pitched, should be a (4:12) slope or greater. See here for information on pitch.

• Pitched roofs generally have fewer problems than “flat” roofs.

The cost of roofing is minor compared to overall project costs, whereas problems with a roof can be some of the most expensive and damaging. Therefore it is best to design and specify quality roofing systems. A roofing system, flashing details, parapets, etc. are not the area of the project to value engineer a cheaper product or system.

‘Flat’ Roofs

All roofs, decks and other flat surfaces should have a minimum slope of ¼” per foot (1:48) to avoid standing water. All ‘flat’ roofs always have a slope… and there is no such thing as a ‘flat roof’ in reality.

Flat roofs are susceptible to Ponding. Ponding occurs when a small depression occurs on the roof surface, either through deflection/sagging or poor construction, which then gathers water. The water weight gathers more water causing it to deflect more, and the cycle continues until ultimately the roof fails in that location. Ponding is a critical problem that needs to be solved as soon as possible.

Estimation

When describing roofing material and estimating size, Squares are used. Square = 100ft2 (10’x10’)

• Squares are aligned with the surface of the roof, and therefore a satellite image cannot be used purely without adjusting for the slope. When viewing a satellite image for estimation purposes, the area from the satellite must be multiplied to account for the slope.