Choosing to replace roof shingles is a major investment for most homeowners, so it makes sense to replace other roofing components to protect the integrity of the roof and home for as long as possible. In nearly all cases, it pays to replace all the flashing if you replace all the roof shingles.
However, certain sections may be as strong as ever. Plus, choosing to not replace every flashing component will lower the cost of the roof replacement. Educate yourself on where flashing is commonly installed and if it should be replaced.
Common Flashing Components
Drip Edge Flashing
Drip edge flashing serves to protect the gutter edge and the roof rake edge.
Both direct water away from the roof and the fascia system.
Drip edge flashing comes in 10-foot strips and is installed to the roof deck before the underlayment goes on. Unless the drip edge is in nearly flawless condition, it should be replaced with the roof.
Gutter flashing should almost always be replaced unless you don’t want to remove decorative guttering because it is attached with spikes or screws through the existing drip edge.
If this is the case with your home, overlay the current drip edge with a new gutter apron and cut the bottom edge of it to accommodate the spikes.
Roof penetrations include vents, chimneys, ridge caps, and more. They should be outfitted with metal or rubber flashing to seal the penetrations.
Like drip edge flashing, penetration flashing should be replaced unless it’s in pristine condition.
Roof valleys are where two roof planes come together and often receive the majority share of water flow on a roof. They greatly benefit from new flashing and additional precautions.
One of the best precautions is to install a waterproof membrane in the valley over the roof deck before laying down the underlayment. Next, roofers can install metal flashing over the underlayment and finally seal the roof with shingles.
Vertical Wall Flashing
Vertical wall flashing is installed where a roof plane meets a wall, like a dormer, chimney, or split-level roof.
Because of their location, these flashings are not always easy to remove and replace. In almost every circumstance of a roof replacement, vertical wall flashing should be replaced. Old flashing can be cut away with metal snips or torn out after prying up clapboard siding.
Old flashing should be replaced.
A natural question to ask is, “If the flashing wasn’t compromised, and wasn’t causing leaks on the old roof, why can’t I keep it when installing new shingles?”
The easiest answer is: you can, and there’s a possibility everything will be fine. However, it’s not the best practice. Local building codes do allow the reusing of flashing, but interesting enough, no shingle manufacturers recommend leaving old flashing in place.
That’s because when you reuse flashing on a roof replacement, the nails don’t always go back in the same holes they were in originally. When you replace an older roof, say a 15-year shingle roof, it’s hard to determine:
How the flashing was originally installed. Was it nailed in properly?
Has the flashing been repaired in the past? And if so, what kind of repair was made?
How many times has the flashing been repurposed over its lifetime?
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Flashing installations require expertise.
Installing new flashing is a relatively straightforward process, but techniques like counter flashing or step-type flashing installations require some expertise. And because flashing covers the most vulnerable sections of the roof, it pays to have a knowledgeable professional replace them.