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79 PhotoOne of the most costly home maintenance tasks that a homeowner may face is the replacement of the roof of their home. The installation of roofs and the reroofing of buildings are governed by the provisions of the California Building Code and the Manufacture’s written installation instructions. It is important that the procedures for reroofing, as stipulated by the California Building Code and the Manufacturer‘s specifications, are followed by the homeowner or contractor to realize the maximum number of years of roof protection and safety to the home. These pages will answer many reroofing questions that are frequently asked by homeowners.

How is the need for a new roof determined?

The most obvious indication for the need of a new roof is the leaking of water in several locations, or if the roof is 20 years old or older. Many times a roof’s life can be extended temporarily through repairs of the leaking area; however, the final decision to replace the roof should be made with the assistance and opinion of one or more local licensed roofing contractors who are experienced in this field. Licensed roofing contractors are listed in the local phone directory. The contractor should inspect for blocked gutters that can cause water to back up under the shingles and cause rot, and should look for worn out roof covering and broken shingles and shakes. At the same time the contractor should check for rusted or loose flashing, which can cause water leaks and fungus/moss growth, which can cause decay and deterioration.

Why is a building permit required to reroof a structure?

Building permits and the procedure for applying new roofs and reroofing is covered in the California Building Code. Before a reroofing permit is issued, the roof specification is reviewed by the Building Division to ensure the roofing material and application complies with the Building Code Standards and the Manufacturer’s installation requirements. Inspections of the roof are made as work progresses. This checking and inspection verifies that the work is completed in a satisfactory manner and the project complies with State Building Codes.

Is it necessary to hire a roofing contractor or can the homeowner replace a roof?

Many homeowners choose to reroof their home to save the cost of labor. There are provisions in the Building Code that allow this practice. The procedures for reroofing remain the same whether a homeowner applies the roof or if a roofing contractor is hired to do the work. The building inspector through the inspection process, will the roof for proper application in accordance with the Building Code Standards and Manufacturer’s recommendations regardless of the installer.

Can a new roof covering be applied over an existing roof?

The building official may permit the recovering of existing roofing based on the condition of the roof and type of roof to be applied if the following general rules are applied:

  • Built up roofs: Built up roof covering shall be completely removed before applying the new roof covering.


The Building Official may allow existing roof coverings to remain when inspection reveals all of the following conditions:

  • That the roof structure is sufficient to sustain the weight of the additional dead load of the roof covering.
  • Fire retardant requirements are maintained.
  • The existing roof covering is securely attached to the deck.
  • The roof is structurally sound.
  • The existing insulation (if installed) is not water soaked
  • Roof drains and drainage are sufficient to prevent extensive accumulation of water.

  • Asphalt shingles: No more than two overlays of asphalt shingles shall be applied over one existing asphalt shingle roof or wood shingles.

  • Wood shakes: New roof coverings shall not be applied over an existing shake roof unless the new roof covering has a special fire retardant listing approved by the International Conference of Building Officials. One overlay of wood shingles can be applied over existing asphalt or wood shingle roof with a slope of 4 and 12 or greater.

  • Wood shingles: One overlay of wood shingles may be applied over existing asphalt or wood shingles.

  • Tile roofs: Tile roof may be applied over existing roof coverings when approved by the building official and substantiated by structural data indicating that the existing roof framing system is adequate to support the additional weight of the tile covering, and the roof slope is 4 and 12 or greater.

How can a reputable roofing contractor be located?

There are many local reputable roofing contractors. Roofing contractors are licensed by the Contractor’s State License Board, are bonded and carry workman’s compensation insurance for their employees. Ask to see a copy of the Contractor’s Warranty which lists the name of the company, State contractors License number, and the expiration date. Check with the Contractors State License Board and the Better Business Bureau for any complaints against the company.

Who is responsible for obtaining the building permit?

Reroof permits can be obtained by the homeowner or a licensed contractor. It is unlawful to commence work on a reroof project without first obtaining a permit. The homeowner can take out the permit for the contractor; however this practice is not recommended. The owner of the property is the person who is ultimately responsible for insuring that a reroof permit is issued.

Is a permit required to replace some missing or broken shingles or shakes?

Minor roof repairs are considered roof maintenance and do not require a permit. However, when a roof covering exceeds 100 sq. ft., by ordinance, it is considered a reroof and a permit is required.

Does the new roof need to be inspected by the Hercules Building Division?

The City of Hercules Building Division inspects all reroof projects for which a building permit is issued. Built up roofs are inspected after the roofing is torn off and all rotten or damaged roof has been removed and replaced. Shake and shingle roofs are inspected after the existing roof has been removed and the new sheathing has been nailed. Metal roofs are inspected after installation of the nailing battens and required fire stopping.

All of the roofs require a final inspection upon completion of the work. It is the responsibility of the homeowner or the contractor to insure that all inspections have been made including the final inspection.

If the roof is replaced with shakes or shingles must they be fire retardant?

Fire Department regulations require the use of Class B treated fire retardant shakes or shingles.

Do the flashings, gutters, and roof jacks need to be replaced?

On a built up roof, vent flashings, metal edging, drain outlets and metal counter flashing shall be removed and cleaned. Rusted or damaged metal shall be replaced. The metal shall be painted with primer prior to installation. On a shingle or shake roof, rusted or damaged flashings, vent caps and metal edgings shall be replaced with new materials as necessary.

What about restoring the shakes instead of replacing them?

The restoring of shakes consists of power washing the roof to remove loose dirt and fungus from the roof and then applying oxalic acid to enhance the wood color. Shakes that are deteriorated or broken shall be replaced, and then wood preservative and fire retardant chemicals are applied. Most companies guarantee the work for five years and offer a longer maintenance contract for an additional cost which extends the guarantee period on a pro rated basis.

Can shingles replace tar and gravel on a roof that is flat or with a slight slope?

The building code states that asphalt shingles are not allowed on slopes less than 2 inches of vertical rise for every horizontal foot of run on the rafter. For asphalt shingles installed on slopes of 2:12 to less than 4:12 the shingles must be self sealed and installed with 2 layers of type15 felt underlayment. Wood shingles are not permitted on slopes less than 3:12 and wood shakes are not permitted below 4:12

What maintenance is required for the roof?

Inspect the roof at least once a year. Clean the roof drains of leaves and debris which could plug roof drains. Notify a roofing contractor if a leak occurs. Do not allow foot traffic on the roof in very cold or hot weather. Concrete tiles should be inspected periodically by a qualified roofing contractor for replacement of broken tiles or leaking metal flashing.

If a problem occurs with the new roof, who does the homeowner contact?

If a licensed contractor installed the roof, the roof should be covered by a warranty. If the contractor refuses to make good on the corrections or repairs to the roof, then the Contractor’s State License Board should be contacted.

Can a shake, shingled or concrete tile roof be applied over spaced sheathing?

Class B treated shingles and shakes can be placed over existing spaced sheathing if the home is located less than 100 feet in elevation. Concrete tile roofs must be applied over continuous sheathing.