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St Louis Roofing: Article About Flashing and Roof Penetrations

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Roof penetrations, including chimneys and skylights, pose leak threats to structures when not sealed properly. St Louis roofing professionals take their time around penetrations to install the right flashing configurations. Contractors can't rely too heavily on sealants because these adhesives tend to shrink and crack over time. Homeowners should know how a proper flashing installation works around penetrations to be confident about contractors' workmanship.

Homeowners are often familiar with step flashing because it's one of the most common metal pieces on a rooftop. Contractors apply step flashing against a penetration, displaying an L shape at the transition point. Both sides of the step flashing are fastened to the different materials, such as the rooftop and chimney surface. This metal protects the penetration transition from any moisture damage. However, step flashing cannot stand alone and still be effective through the years.

Another metal piece functions to cap the step flashing on the penetration's surface. Counter flashing has a rough L shape, and it is installed upside down. The main L length covers the step flashing's top section, creating a protective surface for water to flow away from the transition. The short L section attaches to a crevice, such as chimney brick seams. The step flashing cannot be compromised with leaks because the counter flashing covers its top half almost entirely.

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Reputable contractors take great care to make this transition as protected as possible.

The counter flashing's connection point with the penetration must be sealed from any moisture infiltration. Contractors use specialized sealants to fill these spaces so that counter flashing and penetrations appear to have a seamless look when sealed properly. There shouldn't be any large sealant lumps or uneven surfaces, given that a poor installation will only encourage weathering and possible cracking over time.

Homeowners and contractors can decide if shingles should be added across these flashing sections for aesthetic reasons only. Shingles don't have the protective power at transition points to be effective during rains. However, flashing's metal appearance might be unsightly for some homeowners. Contractors can add some shingles to the metal, creating a uniform look across the roof and around penetrations.

Water flowing away from a penetration on a pitched rooftop, such as below a chimney, can have considerable volume. Contractors install apron flashing sections below these penetrations to give the surface even more protection against possible leaks. This flashing is relatively long as it extends down the rooftop. With proper installation, apron flashing prevents leaks for several decades.

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