Build a Better Home: Roofs

Roof installation stepsA home's roof provides the first line of defense against the greatest source of unwanted moisture in and around a building: rain. Both the overall design of the roof and the finishing materials are important factors in designing a building to withstand moisture penetration.

Roofing systems fall into two categories: near-flat or low-slope and steeply pitched. The roofing system, whether pitched or low-slope, is made up of a number of different components:

  • Roof sheathing
  • Underlayment
  • Roofing material
  • Roof intersections
  • Flashing details
  • Ventilation

Steeply pitched roof systems rely on the force of gravity and the surface friction of the roofing materials to direct the flow of water downward and outward. These systems rely on a series of overlapping elements to redirect rainfall:

  • Roofing felts
  • Shingles
  • Tiles
  • Flashing details

The pitch of the roof provides the gravity and the detailing provides the redirection.

In low-slope roofing systems, water is kept outside of the building envelope by providing a perfect waterproofing barrier over the entire roof system and around every penetration in the roof. Instead of providing the redirecting force to channel water away from the inside of the building envelope, the force of gravity drives the water into every imperfection in the waterproofing system. Moderately high winds can force water to collect in areas that would normally drain adequately. Once standing water is present, even minor defects can cause major water leaks.


Get the Brochure

Build a Better Home: Designing Roofs to Prevent Moisture Infiltration

 

APA's Designing Roofs to Prevent Moisture Infiltration brochure, available for free download in PDF format from the APA Resource Library, describes the various weatherproofing methods used to keep water away from the interior.


Watch the Videos

 

These video segments are excerpted from the Build A Better Home: Moisture Control in Residential Construction video produced by APA. You can purchase the complete 25-minute video from the APA Ressource Library. Please refer to current APA literature and consult your local jurisdiction or design professional to assure proper compliance with code, construction and performance requirements.

Roof

Shingling & Venting

Installing a Cricket

Ice Dams


Download Construction Details

Click on "JPG" to download the associated detail.

Roofs JPG
Roof Sheathing  
Roof system components jpg download
APA structural panel roof sheathing jpg download
Underlayment  
Single-layer underlayment for steep slope  
Underlayment centered in valley jpg download
Wood Shake Application jpg download
Ridge Intersections  
Shingle roof ridge details jpg download
Slate roof ridge details jpg download
Pan and cover tile roof ridge details jpg download
Wood ridge detail for shake- or shingle-type roofs jpg download
Valley Intersections  
Typical metal open valley flashing jpg download
Closed mitered valley with interwoven valley flashing jpg download
Rolled roofing material for open valley construction jpg download
Woven valley jpg download
Hip Intersections  
Mitered hip with slate roofing and interwoven hip flashing jpg download
Asphalt roof hip detail jpg download
Hip detail for clay or concrete tile jpg download
Flashing  
Drip-edge metal flashing at roof eaves and rakes jpg download
Plumbing vent stack with pan-and-cover tile jpg download
Chimney flashing step 1 jpg download
Chimney flashing step 2 jpg download
Chimney flashing step 3 jpg download
Chimney flashing step 4 jpg download
Chimney flashing step 5 jpg download
Chimney flashing step 6 jpg download
Chimney flashing step 7 jpg download
Counter flashing details jpg download
Counter flashing installation on slope jpg download
Skylight flashing with shingle-type flat roof jpg download
Skylight flashing with cover and pan concrete/clay tile jpg download
Shingle-type roof at sloped wall-to-roof intersection jpg download
Shingle-type roof at horizontal wall-to-roof intersection jpg download
Ventilation  
Cathedral ceiling with continuous ridge vents jpg download
Ice Dams  
Sealed asphalt saturated felt underlayment jpg download
Asphalt saturated felt underlayment jpg download