Requirements for Overlay Roofing in Oklahoma

Materials

• According to Section R907.5 of the IRC Code, you may reinstall your old slate, clay or cement tiles unless they’re damaged, cracked or broken. Aggregate surfacing materials, which include crushed stone, crushed slag or water-washed gravel, must not be reinstalled because they might be contaminated with asphalt. Section R907.4 of the IRC Code states that if a flammable concealed space will be created by installing a new roof over wood shingles or shakes, then you must cover the entire area with gypsum board, mineral fiber or glass fiber and attach it firmly in place.

Loads

• According to the National Roofing Contractors Association, the components of a roof system include the roof covering, the sheathing, the rafters and trusses, and the flashing. Section R907.2 of the IRC Code states that the structural roof components must be able to support the roof covering system, material and equipment loads during construction. In addition, you will need to take snow and wind loads into consideration. The 2009 edition of the IRC code includes span tables for joists and rafters, plus tables that list the minimum allowable deflections for rafters.

Replacement

• If your existing roof covering has deteriorated or is water-soaked, or if you already have two or more types of roof covering installed, Oklahoma requires you to remove the entire old roof covering before installing a new one. You’re also not allowed to reroof over wood shake, slate, clay, cement or asbestos-cement tile. If your old roof is covered in asphalt shingles, you’ll need to remove them before installing a new roof if you live in an area where moderate or severe hailstorms occur.

Exceptions

• The IRC permits some exceptions to the regulations requiring replacement rather than reroofing. Section R907.3 states that existing roof coverings don’t have to be removed if you’re installing a complete and separate roofing system that doesn’t depend on the existing roof for support because it transmits roof loads directly to the structure of the building. You can install metal panel, metal shingle, and concrete and clay tile roof covering over wood shake as long as you are following Section R907.4, which is described under “Materials.” You also don’t need to remove your existing covering if you’re applying a new protective coating over a spray polyurethane-foam roofing system.

Flashings

• You may reuse your vent flashing, metal edgings, drain outlets, collars and metal counterflashings as long as they’re not rusted or damaged. If you’re going to apply bituminous materials to the metal flashing, you’ll need to prime it before you install it. The 2009 IRC code also requires you to follow the manufacturer’s installation instructions when you’re installing flashing.