asphalt shingles

Roof Replacement/Installation

Building permits are required for all roofing projects. Submit your application to the Inspections Department at City Hall. Building permits for roofing are generally issued at the time of application.

All contractors engaged in roofing work must have a state contractors license and show proof of the license to obtain a permit. Specific questions regarding contractor licenses should be directed to the Minnesota Department of Commerce.

Code requirements and roofing information

Download "Roofing: An Overview of Permit and Code Requirements" or read information below.

The scope of this page is limited to the installation of four types of roofing materials: asphalt shingles, mineral-surfaced roll roofing, wood shingles, and wood shakes. For information on other roof coverings such as metal paneled roofs, metal shingles, clay and concrete tile, slate shingles, built-up roofs, modified bitumen roofing, single ply membrane roofs, sprayed polyurethane foam roofing, or liquid applied coatings, please contact the Inspections Department.

General Information

All roof covering materials must be delivered in packages bearing the manufacturers identifying marks and approved testing agency labels when required.

All asphalt shingles must be either self-sealing or interlocking.

The code requires that roof decks be solidly sheathed for asphalt shingles or mineral-surfaced roll roofing. Solid sheathing may be plywood, OSB, or 1-inch nominal boards.

Wood shingles and shakes may be applied over solid or spaced sheathing.

Re Roofing (R907)

New roofing may be installed over an existing roof but is limited to a total of two layers.

Existing flashing in good condition can be reinstalled. Any sheathing that is replaced must be installed per code.

In all cases, the roof structure must be capable of supporting the roof covering system and any loads that will be encountered during the installation of the new roof.

Fastener Schedule for Roofing

Asphalt Shingles

Fasteners for asphalt shingles must be galvanized steel, stainless steel, aluminum, or copper roofing nails, minimum 12 gauge shank with a minimum 3/8" diameter head. They must be long enough to penetrate through the roofing materials and a minimum of ¾" into roof sheathing. When roof sheathing is less than ¾" thick, the fastener must penetrate through the sheathing.

nailing

Mineral-Surfaced Roll Roofing

Roll roofing must be installed in accordance with the manufacturer's installation instructions.

Wood Shingles

Fasteners for wood shingles must be corrosion-resistant with a minimum penetration of ½" into the sheathing. For sheathing less than ½" thickness, the fastener must extend through the sheathing. A minimum of two fasteners per shingle are required.

Wood Shakes

Fasteners for wood shakes must be corrosion-resistant with a minimum penetration of ½" into the sheathing. For sheathing less than ½" thickness, the fastener must extend through the sheathing. A minimum of two fasteners per shake are required.

Ice & Water Barriers

Ice and water barrier location diagram

An ice and water barrier is required on all roofs.* The barrier may be at least two layers of underlayment cemented together or a self-adhering polymer modified bitumen sheet. There are several manufacturers who make materials specifically for this requirement that are marketed under differing trade names. The ice and water barrier must extend from the edge of the eaves to a point 24 inches inside the warm side of exterior wall line of the building. Existing ice barrier membrane may remain if it is adhered to the roof deck. Ice and water barrier is not required in valleys.

*Exception: Detached accessory buildings (garages)

Roof Edging

Roof edging is not required by the code. Some manufacturers may require it.

Ventilation

Enclosed attics should be provided with ventilation as follows:

  • For attics without ceiling vapor barriers, 1 square foot of net free ventilating area should be provided for each 150 square feet of attic area.
  • For attics with vapor barriers or without ceiling vapor barriers and having at least 50% but not more than 80% of the ventilating area provided by ventilators located in the upper portion of the space to be ventilated and at least 3 feet above the eave vents and the balance of the ventilation provided in the eave vents, ventilation may be 1 square foot of net free ventilating area for each 300 square feet of attic area.
  • Ventilation openings must be provided with corrosion resistant mesh with openings of 1/8" to 1/4".

Asphalt Shingles (R905.2)

Asphalt shingles may only be used on roof slopes of 2 units vertical in 12 units horizontal (2:12) or greater. 

For roof slopes from 2:12 to 4:12, double underlayment is required. Underlayment must conform to ASTM D 226 Type I, ASTM D 4869 Type I, or ASTM 6757. 

For roof slopes of less than 4:12, two layers of underlayment are required and must be applied in the following manner. 

For slopes of 4:12 and greater, underlayment must be applied shingle fashion. Laps must be a minimum of 2-inches.  End laps must be offset by at least 6 feet.

For normal application, strip shingles must be fastened with a minimum of four nails.  For interlocking shingles, two nails are required.

Flashing

Flashing is required at all wall and roof intersections, wherever there is a change in roof slope or direction, and around roof openings. When flashing is metal, it must be corrosion resistant metal with a thickness of not less than 0.019 inch (No. 26 galvanized sheet). (R903.2.) 

Valleys must be lined in accordance with the shingle manufacturers written instructions. In addition, valleys may be of any of the following:                                  

  • For open valleys lined with metal, the valley lining must be at least 24 inches wide and of galvanized steel of at least 26 gage or other approved materials.
  • For open valleys, two plies of roll roofing may be permitted. The bottom layer must be at least 18 inches wide and the top layer at least 36 inches wide.
  • For closed valleys (valleys covered with shingles), valley lining of one ply of smooth roll roofing complying with ASTM D 6380 Class S Type III, Class M Type II, or ASTM D 3909 and at least 36 inches wide or one of the two methods previously listed may be used.

Crickets or saddles are required on the ridge side of any chimney or penetration greater than 30 inches wide. Cricket or saddle coverings must be of sheet metal or of the same material as the roof covering.

Flashing against a vertical sidewall must be by the step-flashing method. Flashing against vertical front walls, soil stacks, vent pipes, and chimney flashing must be in accordance with the asphalt shingle manufacturer’s printed instructions

flashing

Kick Out Flashing (R903.2.1)

Locations

Flashings must be installed at wall and roof intersections, wherever there is a change in roof lope or direction and around roof openings. Kick-out flashing/diverters must be installed to divert the water away from where the eve of a sloped roof intersects a vertical sidewall. The kick-out flashing must be a minimum of 2 ½” long.  Where flashing is of metal, the metal shall be corrosion resistant with a thickness of not less than 0.019 inch (No. 26 galvanized sheet).

kick out flashing

Existing buildings and structures

Kick-out flashing is required in accordance with section R903.2.1 when simultaneously re-siding and re-roofing existing buildings and structures.

Kick-out flashings are not required when only re-roofing existing buildings and structures.

Mineral Surface Roll Roofing (R905.5)

Mineral surfaced roll roofing may only be applied on roofs with a slope of 1:12 or greater. Mineral surface roll roofing must conform to ASTM D 3909 or ASTM D 6380, Class M. Mineral surface roll roofing must be installed in accordance with the manufacturers installation instructions.

mineral surfaced roll roofing

Wood Shingles (R905.7)

Wood shingles must be installed on slopes that are at least 3:12 or greater. They must be made of a naturally durable wood of grades 1, 2, or 3 approved by the Cedar Shake and Shingle Bureau. wood shingle gradeA label of an approved grading or inspection bureau or agency must identify each bundle of shingles.

Wood shingles must be installed in accordance with the manufacturers instructions and the following. Wood shingles must be laid with a side lap of not less than 1 ½" between joints in courses and no two joints in any three adjacent courses shall be in direct alignment. Spacing between shingles may not be less than ¼" nor more than 3/8". Weather exposure may not exceed what is specified in the accompanying table.

Wood shingles must be attached to the roof with two fasteners per shingle. Fasteners should be not more than ¾" from the edge of the shingle and not more than 1" above the exposure line.

Wood Shingle Weather Exposure and Roof Slope

Roofing Material Length (inches) Grade Exposure (inches)
3:12 pitch to < 4:12 4:12 pitch or steeper
Shingles of naturally durable wood 16 No. 1 3 ¾ 5
No. 2 3 ½ 4
No. 3 3 3 ½
18 No. 1 4 ¼ 5 ½
No. 2 4 4 ½
No. 3 3 ½ 4
24 No. 1 5 ¾ 7 ½
No. 2 5 ½ 6 ½
No. 3 5 5 ½

wood shingles


wood shingles


Wood Shakes (R905.8)

Wood shakes must be installed on roof slopes of 3:12 or greater and must be installed in accordance with the manufacturers installation instructions and the code.

Wood shakes must be laid with a side lap of not less than 1½ inches between joints in adjacent courses.

Spacing between shakes in the same course must be between 1/8 inch and 5/8 inch for shakes and taper sawn shakes of naturally durable wood and ¼ inch and 3/8 inch for preservative taper sawn shakes.

Fasteners for wood shakes must be corrosion resistant. Shakes must be attached with two fasteners per shake. Fasteners must be positioned not more than 1 inch from each edge and not more than 2 inches above the exposure line.

The starter course at the eaves must be doubled and the bottom layer may be 15-inch, 18-inch, or 24-inch wood shakes or shingles. Fifteen-inch or 18-inch wood shakes may be used for the final course at the ridge. Shakes must be interlaid with 18-inch-wide strips of No. 30 felt shingled between each course in such a manner that no felt is exposed to the weather by positioning the lower edge of each felt strip above the butt end of the shake it covers a distance equal to twice the weather exposure. Underlayment must comply with ASTM D 226, Type I.

Wood Shakes Weather Exposure & Roof Slope

Roofing Material Length (inches) Grade Exposure (inches)
4:12 pitch or steeper

Shakes of naturally durable wood
18 No. 1 7 ½
24 No. 1 10
Preservative-treated taper sawn shakes of naturally durable wood
18 No. 1 7 ½
24 No. 1 10
18 No. 2 5 ½
24 No. 2 7 ½
Taper-sawn shakes of naturally durable southern yellow pine 18 No. 1 7 ½
24 No. 1 10
18 No. 2 5 ½
24 No. 2 7 ½

Wood Shake Application

wood shake application

Gutters & Drainage

Gutters are not required by the code. Gutters may be useful in directing water away from buildings reducing erosion, settlement, and wet basements. Lead-outs on downspouts should extend far enough from the building to effect positive drainage.

Disposal of Debris

The removal of existing roofing materials often results in debris moving about the neighborhood on windy days. Shingle wrappers and other construction debris also end up in neighbors' yards. As you install a new roof on your dwelling, regularly police your yard and adjoining areas for debris that may blow around.

Dumpsters must be kept on private property unless a dumpster permit is obtained from the Public Works Department to place them on the street. Proper positioning of warning signs and markers are important to insure the safety of motorists.

 

NOTICE: This information is intended as a guide to the subject matter and is based in part on the 2015 Minnesota State Building Code and Hopkins City Ordinances. While every attempt has been made to insure the correctness of this information, no guarantees are made to its accuracy or completeness. Responsibility for compliance with applicable codes and ordinances falls on the owner or contractor. For specific questions regarding code requirements, refer to the Minnesota Building Code.

Contacts

  • Administrative Assistant

    952-548-6320

Inspections

Two inspections are generally required for typical roof installations. You will be given an inspection record card with your permit that includes the type of inspections you need to call for and a phone number.

  • The first inspection is the roof deck and ice and water barrier inspection. Your inspector will determine that the condition and type of deck is appropriate for the roofing material you are using and that the ice and water barrier is being installed.
  • The second inspection is a final inspection when all work is complete.