Zinc Strip
A zinc strip is a 6-inch-wide roll of thin galvanized metal installed along the ridge cap of a roof to provide long-term, passive algae and moss suppression. When it rains, water washes over the zinc and picks up trace zinc ions, which then flow down the shingles and create a biostatic environment that prevents algae, moss, and lichen from establishing colonies. A single properly installed zinc strip at the peak can keep an asphalt shingle roof clean for 10-15 years with no further treatment.
In depth
Copper strips are a more expensive alternative and work the same way, with longer-lasting ion release and greater effectiveness against lichen specifically. Both are installed under the last course of ridge shingles and fastened with roofing nails, then caulked where exposed. Zinc strips are one of the most cost-effective upgrades available after a roof cleaning, dramatically extending the service life of the clean result. We offer them as an add-on at every roof cleaning job in Dane County.
How this shows up on our jobs
After every roof soft wash in Madison, we offer zinc-strip installation as an add-on. Most customers who've done it once never go without it — the 10-year suppression is that effective in Wisconsin's humid summers.
Services where this matters
Related terms
Gloeocapsa Magma
Gloeocapsa magma is a photosynthetic cyanobacteria that feeds on the limestone calcium carbonate filler embedded in asphalt shingles. It is the organism responsible for the black or dark-gray streaks that run from ridge to eave on millions of American roofs. Algae spores are carried by wind, birds, and squirrels, which is why you'll often see streaks appearing on one slope of a roof before the other, and why entire neighborhoods in Madison begin showing streaks within a few years of each other once the spore population establishes locally.
Moss vs. Lichen
Moss and lichen are both organisms that colonize roofs and exterior surfaces in Wisconsin, but they are biologically distinct and require different removal strategies. Moss is a non-vascular plant that holds moisture against the surface — on a shingle roof, trapped moisture under a moss mat accelerates granule loss, lifts shingles, and leads to freeze-thaw damage at the mat's edges. Moss is soft, green, and responds well to sodium hypochlorite soft washing plus a zinc-strip regrowth inhibitor.
Biocide
A biocide is any chemical agent that kills living organisms — bacteria, fungi, algae, mold, mildew, lichen. In exterior cleaning, the most common biocides are sodium hypochlorite (bleach), quaternary ammonium compounds ("quats"), and hydrogen peroxide. Each has a place: sodium hypochlorite is the fastest and most cost-effective broad-spectrum kill; quats provide residual antimicrobial action that slows regrowth on treated surfaces; peroxide is the mildest and is used where chlorine would damage the substrate.
Soft Wash
Soft washing is a low-pressure exterior cleaning method that uses biodegradable detergents and a controlled bleach solution to kill the algae, mold, mildew, and bacteria that cause staining — rather than scouring them off with brute force. A soft wash rig delivers cleaning fluid at roughly 60-200 PSI, comparable to a strong garden hose, which is safe on siding, shingles, painted surfaces, screens, and caulking. The chemistry does the work: the solution dwells on the surface, breaks down the organic growth at the cell level, and is then rinsed clean with fresh water.
Algae vs. Lichen
Algae (most commonly Gloeocapsa magma on roofs) is the photosynthetic organism responsible for the black streaks running down asphalt shingles, the green haze on north-facing siding, and the slippery film on concrete walkways. Lichen is a symbiotic partnership between a fungus and an alga — a completely different, far more persistent organism that looks like a flat crusty patch with a raised perimeter. Lichens physically anchor into the substrate with root-like structures, which is why they do not wash off like algae does.