Roof flashing plays a critical role in guiding water away from vulnerable areas of a roof. When you experience a leak, 95% of the time that leak is likely occurring at a roof flashing point.
Flashing points on a roof consist of anywhere that a roof plane meets a vertical surface. On a residential home, this could be where the roof connects to a dormer window or a chimney. For a commercial roof, flashing is required where the roof meets the parapet wall and around all rooftop penetrations.
Flashing roof penetrations including vent pipes, skylights, and areas where roof planes connect is critical to roof leak prevention. Understanding the role that flashing plays and how it works to keep your home or building leak free will help you make the right decisions when it comes time to repair or replace your flashing.
What Is Roof Flashing and Why Does It Matter?
Roof flashing is the unsung hero of the roof system, and it has the critical job of guiding water away from vulnerable areas so it can safely exit the roof and not infiltrate into the home or building.
Flashing is a thin material, usually galvanized steel, that is installed on the roof where it meets a vertical surface or where two roof sections come together. These intersecting areas must be flashed to prevent water from dripping into the crevice that exists where these points come together. El tapajuntas para techos ofrece un sellado eficaz en cualquier unión o penetración del techo (como una chimenea o respiradero) donde hay una intersección de dos superficies del techo o donde el techo se encuentra con una pared exterior.
El tapajuntas protege estas áreas actuando como barrera y como una forma de dirigir el agua hacia abajo y fuera del techo. Los contratistas instalan el tapajuntas cuando colocan tu sistema de techo, pero siempre puedes contratar a un profesional para agregar o mejorar el tapajuntas después de la instalación.
Roof flashing is installed underneath the shingles on a residential home but will be visible as it must extend a few inches up the side of the vertical surface to ensure the intersecting planes are adequately protected from water intrusion.
Where Roof Flashing Is Critical: The Vulnerable Points
Roof-to-wall intersections are one of the most vulnerable areas on a home or building. If not properly flashed, water will work its way into the wall and likely won’t be noticeable until extensive damage results. Metal flashing on roof-to-wall intersections is typically bent at a right angle and with one side against the wall and the other interwoven with or underneath the shingles.
Roof valleys are more common on residential homes and feature a V-shaped channel where two roof planes meet. This is an extremely critical area of the roof as the shingles will shed water to the lowest point, which is where the two planes meet to form the valley. The valley must be able to handle the water that converges there and be properly flashed in order to guide the water through the valley and off the roof. If it is not properly flashed, the water can creep under the shingles and find its way into the home, leading to wood rot, mold growth, and interior damage.
Chimneys can be a tempting place for water to try to work its way into the home. Water infiltration around the chimney is a big problem for many homeowners. It can be tricky to get the flashing right as chimneys require a waterproof barrier with flashing installed at the base of the chimney, secured to the deck, and then counter flashed to the side of the chimney using mortar. Damaged or failing chimney flashing is a common cause of leaks for homeowners.
Vent pipes are another vulnerable point on your roof. Ventilation is critical as every home needs a way to exhaust moisture that can build up inside the home. Vent pipes on the roof are typically exhausting from the bathrooms in the home, the dryer, or even the stove. Anytime there is a penetration in the roof, they must be flashed properly to prevent water intrusion. The most common flashing for vent pipes is using a rubber boot that slides over top of the pipe and seals tightly against the pipe and the shingles.
Skylights can be another easy way for water to find its way into the home if not properly flashed. Skylights can be either curb mounted or deck mounted but no matter the installation style, they require proper flashing to ensure water is directed away from the skylight and off the roof.
Roof perimeter areas including eaves, gables, and rakes should use drip edge flashing to prevent water from seeping under the edge of the shingle which can lead to wood deck rot. Drip edge helps protect the fascia and guides water into gutters so it can be carried down off the roof and away from the home.
Complete Guide to Roof Flashing Types
Step Flashing
Step flashing is most commonly used for roof-to-wall and roof-to-chimney applications. The L-shaped pieces are typically installed in a stair-step pattern that overlaps the other pieces. Each piece is bent at a 90-degree angle and is eight to ten inches long, allowing for a four-to-five-inch exposure on the wall and four to five inches installed under the shingles.
The Asphalt Roofing Manufacturers Association (ARMA) explains sizing in its residential roofing manual, indicating that size is determined by the shingle exposure. “When used with shingles with a 5" exposure, they should be a minimum of 10" x 7". The 10" length is bent at 90 degrees to extend 5" over the roof deck and 5" up the wall assembly.”
Each step flashing piece is installed at the end of each course of shingles, working up-roof as each row of shingles is installed.
Valley Flashing
Valley flashing is W-shaped metal that is installed where two sloped roof planes meet. This type of flashing is vital for preventing leaks in high-risk areas where large volumes of water are channeled. The W style features a center rib that prevents the water from jumping over the valley and onto the other slope.
There are two styles of valley flashing: open valleys and closed valleys. With open valleys, the metal flashing is visible. This style is usually preferred when installing higher end roofing systems like slate, metal and tile. Closed valleys are more common on asphalt shingle roofs where the shingles cover the metal and it is not visible.
Base and Counter Flashing
Base and counter flashing make up a two-part system that works together to prevent water intrusion. This flashing is most used around chimneys to ensure that rain is hitting a flashing that will direct it down and away from the chimney. Base flashing, sometimes called apron flashing, is the bottom part, and the counter flashing is installed above the base flashing, completing the flashing system.
Because the chimney typically has a separate foundation that sometime is independent of the home, this two-part flashing system allows for independent movement during the expansion and contraction that normally occurs, while still keeping the roof and chimney watertight.
Drip Edge and Specialty Flashing Types
Drip edge is installed along rakes and eaves to help guide water away from the fascia and into the gutters, preventing water from seeping under the shingles. It is required by building code in most areas. An added benefit is that it can also help protect the roof from wind uplift.
ARMA explains the placement of the edge, saying “The drip edge should be made of a corrosion-resistant material that extends a minimum of 2″ (51 mm) onto the roof sheathing and extends downward at least ¼” (6mm) below the roof sheathing.”
The drip edge should have an outward bent flange at the lowest point that is also known as a kickout. This ensures that water is guided into the gutters, avoiding the fascia and the wood deck underneath the shingles.
Other specialty flashing types are available to ensure that flashing roof penetrations such as skylights and vents are leak proof and properly sealed against water intrusion.
Roof Flashing Materials: Complete Comparison Guide
These days, most roof flashing is made of metal, including galvanized steel, copper, and aluminum. Metal flashing can be preformed to fit general specifications or hand-cut to fit unique roof designs.
Acero galvanizado
Galvanized steel is the most common choice of material for roof flashings. Contractors prefer is because it has an appealing appearance, it's moldable and pliable and because it is galvanized, it resists corrosion.
This material is one of the most cost-effective options with prices ranging on average from $1.00 to $1.50 per linear foot. Cost will vary depending on thickness of the steel, the quantity that is being purchased, and the type with specialized shapes costing more than standard styles. Installation costs will also vary widely as factors like complexity and pitch of the roof will affect the price.
Most residential building codes require the use of flashing at chimneys, valleys, rakes, and roof-to-wall intersections that is corrosion resistant, minimum of 26-gauge and made of galvanized steel. Always refer to the local building codes where the home is located as requirements change from jurisdiction to jurisdiction.
Galvanized steel offers a lifespan of 20 – 30 years and shouldn’t require attention during the lifecycle of the asphalt roof when properly installed.
Aluminio
Aluminum is another very durable material that is often used for roof flashings in challenging environments including coastal applications. It is very corrosion and rust resistant, making it a popular choice in areas along the coast with salty air. It is also lightweight, which makes it easier to transport, and its flexibility lends itself well to on-site bending.
The aluminum must be coated to avoid chemical reaction when coming into contact with concrete or masonry as it can lead to degradation. Aluminum is more malleable than steel so there is a risk that it might dent easier.
Compared to steel, aluminum tends to be slightly less expensive option. Keep in mind that prices will vary based on factors including quantity purchased and negotiated pricing the contractor may have with the supplier. Installation costs will vary as well based on the factors mentioned earlier such as pitch and complexity.
Much like steel, aluminum has a comparable life span of 20 – 30 years when properly installed.
Copper and Premium Options
Copper flashing is a high-end flashing that delivers long-lasting protection for any home. It is extremely corrosion resistant and adds an aesthetic appeal to the home as it develops its signature protective patina that develops over time from a dark brown to a light green color. It is consistently chosen as a flashing around chimneys because of its beauty.
It is very malleable, making it ideal for custom applications, plus it has natural properties that allow it to inhibit the growth of moss and algae. It is a very low maintenance solution for flashing that delivers an impressive lifespan of 80 - 100 years when properly installed.
Copper is going to be the most expensive option for flashing with costs ranging anywhere from $10 to $30 per linear foot, depending on size, gauge and amount purchased.
Stainless steel is another premium flashing material that offers similar benefits to copper in terms of corrosion resistance and longevity. Preformed pieces like drip edge are not much more expensive than standard materials; however, thicker gauges and specialized flashings will cost more.
Signs Your Roof Flashing Needs Attention
Although roof flashing is durable, it can deteriorate over time and become damaged or loose, which can lead to leaks. Es una buena idea realizar una revisión anual para identificar problemas con el tapajuntas del techo y ayudar a prevenir posibles inconvenientes.
Puedes revisar el interior de tu techo desde tu ático y realizar una revisión exterior caminando por el perímetro de tu casa con unos binoculares, ¡pero no subas a tu techo! Eso es peligroso para ti y potencialmente dañino para tu techo también.
Dentro de la casa, revisa lo siguiente:
Filtraciones en tu casa, garaje o porche.
Manchas de agua en el cielo raso
Agua visible goteando por la parte posterior de la plataforma o de una chimenea en el espacio del ático
Manchas de agua en el ático
Luz del día que se filtra alrededor de los respiraderos o las tuberías del cielo raso en tu ático.
Desde el suelo fuera de tu casa, revisa para detectar lo siguiente:
Tejas sueltas, dañadas o faltantes
Tapajuntas sueltos, dañados o faltantes
Cualquiera de estos signos podría indicar un problema en el tapajuntas, o bien señalar otros inconvenientes que podrían estar causando filtraciones. De cualquier manera, si ves alguno de estos indicios, lo mejor es que un profesional revise tu sistema de techo de inmediato.
Professional Installation vs. DIY: What Homeowners Need to Know
Installing, repairing and replacing flashing requires special knowledge that most homeowners do not have - even those that typically like to tackle home improvement projects on their own. It's wise to avoid trying to do the work yourself for many reasons, including:
Safety. Working at heights on a roof requires specialized safety training and fall protection gear. Professional contractors are knowledgeable about the dangers and they follow strict safety guidelines that the average homeowner may not be aware of.
Performance. Flashing roof on your own, you could unwittingly cause damage to other areas of your roofing system. If the components of the roofing system are not properly reinstalled or sealed after the flashing installation, materials are not going to provide proper water damage protection for your home.
Warranty implications. Many roofing manufacturers require that any work done on your roofing system be performed by a professional roofing contractor that has been qualified or certified by the roof system manufacturer. By trying to perform the work yourself, you could unknowingly void your roof warranty.
Improper installation. Flashing roof protrusions or intersecting planes requires precision and proper placement of materials. Not understanding the intricacies of the installation puts your home at risk of water intrusion and potential interior damage.
Protecting Your Home Investment Through Quality Flashing
With 95% of roof leaks occurring where penetrations, protrusions and roof planes meet, flashing roof details with the highest quality materials that are installed by a professional contractor is the best way to protect your home from water intrusion and resulting damage.
While most flashing materials do have life expectancy, that in some cases, is longer than the roof itself, the role it plays in protecting the home should not be downplayed. That means that regular roof and flashing inspections should be part of your regular home maintenance plans.
If you find yourself in a situation where you need to replace your roof, you’ll want to be sure that you replace the flashing materials at the same time to ensure the ultimate protection for your home.
¿Listo para que un profesional de confianza inspeccione tu tapajuntas o solucione una filtración? Search for GAF-factory certified* roofing contractors, ready to handle the job, in your area.
*Los contratistas inscritos en los programas de certificación de GAF no son empleados ni agentes de GAF, y GAF no controla ni supervisa de otro modo estas empresas independientes. Los contratistas pueden recibir beneficios, como puntos y descuentos de recompensa por lealtad en herramientas de comercialización de GAF por participar en el programa y ofrecer a GAF garantías mejoradas, que requieren el uso de una cantidad mínima de productos de GAF. Tus tratos con un contratista, y cualquier servicio que te preste, están sujetos a los Términos de uso para contratistas.
