Roof Structure Thickness

The structural engineer must factor in the weight of completely saturated soil since the plantings and the soil will hold a significant amount of water.

Roof structure thickness.

The nominal thickness of a green roof is the approximate total height of the soil and drainage components that constitute the green roof system excluding the roof structure insulation waterproofing and plants. The problem with metal roofing gauge is that there is a wide range of tolerances. Green roofs tend to improve the life of the membrane because it is completely covered by plantings and isn t exposed to the sun s harsh uv rays. That s considered to be the minimum.

This minimum will only work if the rafters are set 16 inches apart at most and if the roof doesn t have too much load. Unlike with plywood siding the plywood sheet to be used for sheathing should be at least 3 8 inch thick. Intensive to describe green roofs that are thick enough. It is also important to factor in the type and lifetime of the roof membrane that will be used.

Comstock comstock getty images the roof of the house must be structurally sound to support the weight of the shingles. It is common practice to use the term extensive to describe green roofs that are very thin and will only support hardy drought resistant vegetation such as sedums herbs and perennials. Sheathing should be a minimum of 19 32 inch thick. As a general rule roofs that have a high human occupancy rate should be framed with rafters every 16 structures such as sheds or barns can be frames with rafters every 24 again make sure to consult local codes.

The typical thickness range for sheathing is 3 8 to 3 4 inch. This is especially true of intensive green roofs which can have soil that is two feet deep or more. 07 60 00 flashing and sheet metal and 07 62 10 copper flashing. For example one company might sell a product as being 24 gauge but in reality the thickness of the metal could vary from 0 018 to 0 0335 based upon exactly how that company looks at things and how big of a tolerance they allow for.

If your project had a rafter length of 8 or less a safe and strong method is to use 2x8 framed 16 on center.