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.
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.
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.
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.
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.
Roll roofing must be installed in accordance with the manufacturer's installation instructions.
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.
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.
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 is not required by the code. Some manufacturers may require it.
Enclosed attics should be provided with ventilation as follows:
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 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:
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
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 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.
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. A 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.
|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 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.
|Roofing Material||Length (inches)||Grade||Exposure (inches)
4:12 pitch or steeper
Shakes of naturally durable wood
|18||No. 1||7 ½|
|Preservative-treated taper sawn shakes of naturally durable wood
||18||No. 1||7 ½|
|18||No. 2||5 ½|
|24||No. 2||7 ½|
|Taper-sawn shakes of naturally durable southern yellow pine||18||No. 1||7 ½|
|18||No. 2||5 ½|
|24||No. 2||7 ½|
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.
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.
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.