Roofing System Training

Roofing Systems

Roofing Framing

Residential Roofing

• Framing:

  • Rafters: The primary structural members that support the roof sheathing. They typically form a triangular shape with the ridge beam and the wall plates.

  • Ridge Beam: The horizontal member at the highest point of the roof, where rafters meet.

  • Wall Plates: The horizontal members that sit atop the walls and support the rafters.

  • Sheathing: The material (usually plywood or OSB) that is attached to the rafters to form the roof deck.

• Common Roof Designs:

  • Gable Roof: The most common type, featuring two sloping sides that meet at a ridge.

  • Hip Roof: Has four sloping sides that meet at a ridge, creating a pyramid-like shape.

  • Gambrel Roof: Features two slopes on each side, with a steeper lower slope and a shallower upper slope.

  • Mansard Roof: Similar to a gambrel roof, but with steeper lower slopes and a flat or nearly flat upper slope.

Commercial Roofing

• Framing:

  • Steel Trusses: Pre-engineered structures that provide strong support for larger roof spans.

  • Bar Joists: Long, narrow beams that span between supporting beams, creating a grid-like structure.

  • Metal Deck: A corrugated metal sheet used as sheathing for commercial roofs.

• Common Roof Designs:

  • Flat Roof: A horizontal or nearly horizontal roof, common in commercial buildings.

  • Low-Slope Roof: Has a slight slope to allow for drainage.

  • Curved Roof: Used in some architectural styles for aesthetic appeal.

Roofing Materials

Residential Roofing Materials:

• Asphalt Shingles: The most common type, known for their affordability and durability.

• Wood Shingles/Shakes: Natural materials that provide a rustic appearance, but require more maintenance.

• Metal Roofing: Durable and energy-efficient, available in various styles and finishes.

• Tile Roofing: Long-lasting and aesthetically pleasing, but can be more expensive.

• Slate Roofing: High-end, durable, and visually appealing, but also very expensive.

Commercial Roofing Materials:

• Built-Up Roofing (BUR): Multiple layers of asphalt and tar, often used for flat roofs.

• Modified Bitumen Roofing: Similar to BUR, but uses polymer-modified asphalt for improved performance.

• EPDM Roofing: (Ethylene Propylene Diene Monomer) A single-ply rubber membrane, known for its durability and flexibility.

• TPO (Thermoplastic Polyolefin): A single-ply membrane that is lightweight and easy to install.

• Metal Roofing: Durable and energy-efficient, often used for low-slope and flat roofs.

Roofing Installation and Maintenance

• Installation: Proper installation is crucial for the longevity and performance of a roof. It should be carried out by qualified professionals according to manufacturer's instructions and local building codes.

• Maintenance: Regular roof inspections, cleaning, and repairs can help extend the lifespan of a roof and prevent costly damage.

• Safety Considerations: Roofing work can be dangerous. Always use appropriate safety equipment, such as harnesses and fall protection systems, when working on a roof.

I. Underlayments: The Secondary Line of Defense

These are the materials laid directly on the roof deck before the final roofing material. They provide critical secondary protection against water intrusion.

1. Ice & Water Shield (Self-Adhered Underlayment)

   • What it is: A specialized, self-adhering (peel-and-stick) membrane typically composed of a rubberized asphalt adhesive surface with a tough, waterproof top film.

   • Where it's located:

     • Eaves (Ice Dam Zone): Along the bottom edge of the roof, extending from the fascia board upwards (e.g., 24 inches past the interior wall line in colder climates like Massachusetts). This is crucial for preventing leaks from ice dams (where melted snow refreezes at the eaves, backing water up under shingles).

     • Valleys: Along all roof valleys where two roof planes meet, as these are high-flow water channels.

     • Around Penetrations: Around chimneys, skylights, plumbing vents, and other roof penetrations where the roof deck is interrupted.

     • Low Slope Areas: Sometimes applied as a full coverage underlayment on roofs with very low slopes that are more prone to water penetration.

   • Why it's essential: Its self-sealing adhesive properties create a watertight seal directly to the roof deck, preventing water penetration from ice dams, severe wind-driven rain, or water that might get past the primary roofing material due to damage or extreme weather. It is the first line of absolute waterproof defense in critical areas.

2. Felt Paper (Asphalt Felt / Roofing Felt)

   • What it is: A traditional roofing underlayment made from organic or fiberglass mat impregnated and coated with asphalt. It comes in rolls, typically 15-pound or 30-pound weight (though metric equivalents are now common).

   • Where it's located: Applied over the entire roof deck, on top of any Ice & Water Shield. It is laid in horizontal courses, overlapping each course to shed water.

   • Why it's important:

     • Secondary Water Barrier: Provides a critical layer of protection if the primary roofing material (shingles) is damaged or dislodged. It can prevent minor leaks.

     • Temporary Protection: Protects the roof deck during construction before the final roofing material is installed.

     • Shingle Separation: Prevents the roofing material from sticking to the wood deck, allows the deck to breathe, and provides a uniform surface for installation.

   • Modern Alternative: Synthetic underlayments are increasingly popular. These are lighter, stronger, less prone to wrinkling, and often have higher tear resistance than traditional felt paper, offering superior protection.

II. Flashing & Penetration Seals: 

These metal or composite components are strategically installed at roof intersections and penetrations, which are inherently vulnerable points for water intrusion.

1. Drip Edge

   • What it is: A non-corrosive metal flashing (often aluminum or galvanized steel) with an angled or "kick-out" flange.

   • Where it's located: Installed along the eaves (lower edge) and rake edges (gable ends) of the roof, underneath the underlayment at the eave and over the underlayment at the rake.

   • Why it's vital:

     • Directs Water: Directs water off the roof and into the gutters, preventing it from running down the fascia board and potentially rotting the wood.

     • Protects Roof Deck: Prevents water from wicking back underneath the roofing materials and damaging the roof deck or fascia.

     • Secures Underlayment: Helps hold the underlayment and starter course firmly in place at the roof edges.

2. Vent Boots (Pipe Collars / Pipe Flashings)

   • What it is: A pre-formed, often two-piece flashing system designed to seal around circular pipes penetrating the roof deck. It typically consists of a metal base (often galvanized steel or aluminum) with a flexible rubber or neoprene collar that fits snugly around the pipe.

   • Where it's located: Around plumbing vent pipes, furnace/water heater B-vents, and other circular penetrations through the roof.

   • Why it's critical: Pipes create an opening in the roof deck, a prime entry point for water. The vent boot provides a watertight seal around the pipe and sheds water over the surrounding roofing material. Over time, the rubber can crack, leading to leaks, making this a common failure point.

3. Chimney Flashing

   • What it is: A complex system of metal pieces designed to waterproof the intersection of a chimney and the roof.

   • Components:

     • Apron Flashing: A single piece of metal installed on the low side (downslope) of the chimney, extending under the shingles and up the chimney face.

     • Step Flashing: Individual L-shaped pieces of metal woven in with each course of shingles along the sides of the chimney, directing water onto the shingle below.

     • Counter Flashing (or Cap Flashing): Metal strips that are cut into the chimney's mortar joints (or attached to the chimney face) and bent down over the top edge of the step and apron flashing, protecting their upper edges from water intrusion.

     • Cricket (or Saddle): A small, tent-shaped diversion structure built on the high side (upslope) of wide chimneys to shed water around the chimney rather than allowing it to pool behind it. This is often flashed with separate metal pieces.

   • Where it's located: At all four sides of a chimney where it projects through the roof.

   • Why it's essential: Chimneys are significant interruptions in the roof plane and are highly susceptible to leaks if not meticulously flashed. This multi-layered system ensures water is shed away effectively.

4. Valley Flashing

   • What it is: A waterproof membrane (often Ice & Water Shield) and a continuous, typically W-shaped or flat, metal piece (galvanized steel, copper, or aluminum) installed in the "valley" where two roof planes meet and shed water towards each other.

   • Where it's located: In all roof valleys.

   • Why it's critical: Valleys concentrate a large volume of water flow during rain or snowmelt. The metal flashing creates a smooth, durable channel for water to drain efficiently without penetrating the roof deck. The underlying Ice & Water Shield provides a secondary barrier.

5. Wall Flashing (Step Flashing, Headwall Flashing)

   • What it is: Metal flashing used to waterproof intersections where a roof plane meets a vertical wall (e.g., dormer walls, side walls of an addition, parapet walls).

   • Types:

     • Step Flashing: Similar to chimney step flashing, individual L-shaped pieces are woven in with each shingle course along the sides of a wall, directing water over the shingle below. These are typically covered by siding or a separate counter flashing cut into the wall.

     • Headwall Flashing: A single, continuous piece of metal installed where the roof meets a vertical wall at the top (upslope) of a roof plane, often against a dormer. It extends under the shingles above and up the wall.

   • Where it's located: At any point where a roof meets a vertical wall.

   • Why it's vital: These intersections are common areas for leaks. The flashing ensures that water running down the wall or roof is directed away from the vulnerable seam and onto the roofing surface.

The Problem: The "Snow Avalanche" on Metal Roofs

Unlike asphalt shingles or other textured roofing materials that hold snow in place, metal roofs are inherently smooth and have a low coefficient of friction. As the sun warms the metal, even slightly, the snowpack can lose its adhesion to the roof surface. This often leads to large, heavy sheets of snow and ice rapidly sliding off the roof in a sudden, uncontrolled "avalanche."

This phenomenon poses significant risks:

• Personal Injury: People walking beneath eaves, near entryways, or in driveways can be struck by falling snow and ice, leading to serious injuries or even fatalities.

• Property Damage: Gutters can be torn off, landscaping can be crushed, vehicles parked near the building can be dented or destroyed, and lower roof sections or attached structures (like porches or awnings) can be severely damaged.

• Liability: Property owners can face considerable liability and legal action if injuries or damage occur due to uncontrolled snow and ice shedding.

The Solution: Snow and Ice Brakes

Snow and ice brakes are specialized devices designed to retain snow and ice on the roof, allowing it to melt gradually and safely, rather than sliding off in a dangerous mass. They distribute the load of the snow across the roof surface, effectively holding it in place until it thaws or dissipates.

How They Work:

These systems work by creating friction and physical barriers on the otherwise slick metal roof surface. They are installed in strategic patterns to create a grid or fence-like structure that prevents the large, cohesive sheets of snow from gaining momentum and sliding off.

Types of Snow Retention Systems

There are several common types of snow and ice brakes, each suited to different roof profiles and snow loads:

1. Bar-Style Systems (Snow Rails or Fences):

   • Description: These are typically continuous or sectioned metal bars, often 1-2 inches in diameter, mounted horizontally along the roof parallel to the eaves. They are usually supported by brackets that attach to the roof seams (for standing seam roofs) or directly to the roof deck (for exposed fastener roofs).

   • Function: They create a robust, linear barrier that spans the width of the roof, effectively acting as a "snow fence." They are excellent for high-snow load areas and areas requiring maximum protection.

   • Application: Common on commercial buildings, industrial facilities, and residential homes with steep pitches and significant snow accumulation.

2. Pad-Style Systems (Individual Snow Guards or Cleats):

   • Description: These are individual, small, often clear or colored plastic, polycarbonate, or metal "pads" or "cleats" that are installed in a staggered pattern across the roof surface. They may have a small "foot" or "blade" that protrudes upwards.

   • Function: They work by "pinning" the snow in place. The individual guards create a distributed network of points that prevent the entire snow mass from sliding. They allow for some gradual trickling of melted snow beneath the snowpack.

   • Application: Widely used on residential metal roofs where aesthetics are a concern, as they can be less visually intrusive than bar systems. They are typically installed in multiple rows depending on roof pitch and length.

3. Hybrid Systems: Some systems combine elements of both bar and pad styles, or offer more decorative options that blend with the roof's aesthetic.

Installation and Placement Considerations

Proper installation is critical for the effectiveness and longevity of snow retention systems.

• Strategic Placement: Snow and ice brakes are most crucial over high-traffic areas such as:

  • Building entrances and exits.

  • Walkways and sidewalks.

  • Driveways and parking areas.

  • Lower roof sections or attached structures (porches, awnings, dormers).

  • Around chimneys, skylights, or other penetrations where ice can build up.

• Roof Type-Specific Attachment:

  • Standing Seam Metal Roofs: Most systems use non-penetrating clamps that attach directly to the vertical seams of the roof panels. This is ideal as it maintains the integrity of the roof and doesn't create new points of potential leakage.

  • Exposed Fastener Metal Roofs: Systems for these roofs often require screwing through the metal panels into the roof purlins or decking below. Proper sealing (e.g., using EPDM washers or sealant) is paramount to prevent leaks.

• Engineered Design: The number of rows, spacing between guards, and type of system selected should be determined based on:

  • Roof Pitch: Steeper roofs require more retention.

  • Roof Length: Longer roof runs accumulate more snow.

  • Anticipated Snow Load: Local snow load data (like that for Leominster, MA) is crucial.

  • Roofing Material/Panel Type: Compatibility with the specific metal roofing product.

  • Climatic Conditions: Regions with freeze-thaw cycles (like the Northeast) can lead to heavier, denser ice formations, requiring more robust systems.

Benefits Beyond Immediate Safety

Beyond the critical prevention of injury and direct property damage, snow and ice brakes offer additional advantages:

• Protection of Gutters: Prevents heavy, sliding snow and ice from ripping off or damaging gutters.

• Protection of Landscaping: Prevents plants, shrubs, and outdoor features from being crushed.

• Even Snow Melt: By holding snow on the roof, it allows for more even melting and reduced thermal shock to the roof system.

• Reduced Liability: Significantly lowers the risk of lawsuits and insurance claims related to falling snow and ice.

• Enhanced Curb Appeal: While functional, many modern systems are designed to be aesthetically pleasing or nearly invisible, blending with the roof.

Parapet Walls: Defining Roof Edges and Enhancing Safety

Functions of Parapet Walls:

• Safety:

  • Parapets act as safety barriers, preventing falls from the roof edge.  

  • They are particularly important on flat or low-slope roofs, where access for maintenance or other purposes is common.

• Weather Protection:

  • Parapets help protect the roof membrane and edge from wind, rain, and snow.  

  • They can also serve as a windbreak, reducing wind uplift on the roof.  

• Fire Resistance:

  • Parapets can act as fire barriers, slowing the spread of fire from one building to another.  

  • This is especially important in densely populated areas.

• Aesthetics:

  • Parapets can add architectural interest and define the building's profile.

  • They can be designed in various styles to complement the building's overall design.

  • They can also be used to hide roof top mechanical equipment from view.  

• Structural Integrity:

  • They can add to the overall structural integrity of the roof system.

Construction of Parapet Walls:

• Materials:

  • Parapets can be constructed from various materials, including:

    • Concrete masonry units (CMU)

    • Brick masonry

    • Reinforced concrete

    • Steel framing with appropriate cladding

    • Wood framing with weather-resistant finishes (less common in commercial due to fire ratings)

• Waterproofing:

  • Proper waterproofing is important to prevent water infiltration.  

  • Flashing, counterflashing, and coping stones are essential components.  

  • The roof membrane must be properly integrated with the parapet wall.  

• Coping:

  • Coping stones or metal caps are used to protect the top of the parapet wall from water damage.  

  • They are typically sloped to shed water away from the wall.  

• Drainage:

  • Proper drainage is essential to prevent water from pooling on the roof and around the parapet.  

  • Roof drains and scuppers are used to direct water away from the roof.  

• Structural Considerations:

  • Parapet walls must be designed to withstand wind loads and other structural forces.  

  • Proper reinforcement and anchoring are essential.

  • In seismic zones, proper engineering is very important.

Key Considerations:

• Building Codes:

  • Parapet walls must comply with local building codes and regulations.  

  • These codes often specify minimum height requirements and structural requirements.