How to Install a Zinc Strip and Properly Close the Ridge on a Metal Roof?

Ever notice dark streaks or moss starting to form near the top of your metal roof? Getting the ridge closure and zinc strip installation right stops those problems for good. I’ve been on crews where skipping these details led to callbacks and leaks within a single season.

• I’ll explain why a zinc strip is your best defense against moss and algae on a metal roof.
• You’ll learn the correct order to install the strip and the ridge cap for a permanent seal.
• I’ll show you the common installation mistakes I find and how to avoid them.

Is This a Job for You? Safety and Skill Assessment First

Let’s be blunt. This work is high, steep, and dangerous. Installing materials at the very peak of a roof is often a pro-only task.

If you decide to proceed, your gear is not optional. You must have it all.

• A full-body harness tied to a certified roof anchor.
• Roof jacks and planks to create a stable work platform.
• A sturdy ladder with standoff stabilizers.
• Rubber-soled, non-slip shoes.

Specific risks change the game. A roof pitch steeper than 6/12 is a different beast. Working near overhead power lines is a deadly hazard. Never work in wet, icy, or windy conditions.

If your stomach drops just thinking about the height, or if power tools make you nervous, this is your sign to call a licensed roofer.

A botched install has real consequences. It can void your metal roof’s material warranty and lead to costly, hidden leaks that ruin your attic insulation and drywall.

What Are Zinc Strips and Why Does the Ridge Need Closing?

Zinc strips are a long-term fix. They are metal bars you install near the roof’s peak. As rainwater runs over them, it carries tiny zinc ions down the roof surface.

These ions create an environment where moss, algae, and mold struggle to grow. Think of it as a low-maintenance, 20-year solution instead of annual pressure washing.

Zinc is often compared to copper. Both work well. Zinc is typically more budget-friendly and tends to leave less noticeable green staining on light-colored roofs.

“Closing the ridge” means sealing the peak where the two roof slopes meet. It’s the final, critical step to lock out water, wind, dust, and insects.

To close it properly, you use closure strips. These are foam or rubber pieces that snap or fit into the ribs of the metal panels right at the ridge.

Are closure strips necessary for metal roofing? Absolutely. They provide a sealed, flexible base for the ridge cap to fasten to. Without them, you have a gaping hole at the top of your house. Note, systems like polycarbonate roofing often use different sealing methods.

An open ridge invites disaster. Water gets driven up under the cap by wind. Your heating and cooling escape. Wasps and bees build nests inside. Eventually, you see stains on your ceiling.

The Science Behind the Strip: How Zinc Fights Moss

The process is simple. Imagine a bar of soap in a rainy gutter. The rain slowly dissolves it, and the soapy water washes over the surface.

Zinc works the same way. Rain dissolves minuscule amounts of the metal. This zinc-ion charged water then sheets down your roof.

This ion layer interferes with the cellular processes of moss and algae, preventing them from taking hold and thriving.

You must be patient. We call it “zinc dieback.” Existing growth may take one to two full seasons to brown out and disappear. The strip prevents new growth but isn’t a magic eraser for a thick, existing moss blanket.

So, do zinc strips actually repel algae, moss, and mold? They don’t repel like a fence. They work by transfer. The ions move with water to coat the roof, creating a surface that inhibits biological growth for years.

Understanding the Ridge as a Primary Leak Point

The ridge is the most critical junction on your roof. If the ridge is the zipper on your winter coat, then closure strips are the weather flap behind it. If that flap is missing, snow and wind get right in.

Other spots leak, like valleys or wall flashings. The ridge is uniquely vulnerable. Wind can actually push water *up* a roof slope during a storm. Without a tight seal at the top, that water has a direct path into your attic.

A properly closed ridge is non-negotiable for the lifespan of a metal roof. It’s the final lock on a system designed to shed water. Getting it wrong undermines the entire installation.

Gathering Your Gear: Tools and Materials Checklist

Never head up the ladder without everything you need. A second trip is a waste of energy and increases your risk. Here is what you will use.

Tools You Will Need:

• Tape measure
• Aviation snips or a metal cutter
• Cordless drill with a hex driver bit
• Caulking gun
• Utility knife
• Chalk line

Materials You Must Have:

• Zinc strips (a 6-inch width is the standard for this job)
• Butyl tape or a sealant made for metal roofing
• Metal roofing screws with sealing neoprene washers
• Ridge cap panel or sections
• Closure strips (use open-cell foam for standard ribs or closed-cell for taller profiles)

Do you have to use closure strips on a metal roof? Yes, you do. They are not optional trim. Closure strips fill the gaps between the roof panel ribs and the ridge cap. This creates the thermal seal and, more importantly, the critical water seal that keeps rain from being driven up under the ridge.

Some ask about furring strips for a metal roof. That is a different issue related to creating a vented airspace over your roof deck. It is a substrate consideration, not part of this ridge and zinc installation for residential metal roofs.

Step-by-Step: Installing the Zinc Strip Under the Ridge Cap

This is the heart of the job. The zinc strip must be installed after the main roof panels are on but before the final ridge cap is screwed down. Think of it as the hidden guardian that works for decades. Next is the roof ridge cap installation, where this strip becomes the shield along the peak. A proper fit here seals the ridge and completes the job.

Step 1: Measure, Mark, and Plan the Run

Measure the full length of your roof ridge. Zinc strips typically come in manageable lengths, like 4 to 6 feet. Plan your segments so the joints will be staggered from the ridge cap joints later.

You will overlap each zinc strip by a solid 2 to 3 inches. This ensures a continuous path for the zinc ions to wash down the roof. Use your chalk line to mark a straight guide on the roof metal just below where the ridge cap will eventually sit. This line is for your screw placement.

Planning your overlaps before you cut saves you from a weak spot right at the ridge.

Step 2: Cut and Fit the Zinc Strips

Put on a good pair of work gloves. The cut edges of zinc can be very sharp. Use your aviation snips to cut the strips to your planned lengths.

Here is a detail many miss. The bottom edge of the zinc strip needs weep holes. Use your snips to cut small, half-inch upward notches every foot or so along the strip’s lower edge.

These weep holes let the rainwater, now charged with zinc particles, flow out onto the roof surface to do its job. Without them, water can get trapped behind the strip.

Step 3: Secure the Strip to the Deck

Place the first zinc strip centered on your ridge, directly on the metal roof panel. Align its top edge with your chalk line. The strip will lay flat.

Pre-drill a pilot hole for your first screw at the top corner. Always fasten at the strip’s top edge. The ridge cap will later cover these screw heads, protecting them and hiding them from view.

Drive in your metal roofing screw with its neoprene washer until the washer is just snug and compressed. Stop. Over-driving will crush the metal, create a leak point, and distort the strip.

Continue placing screws about every 12 to 16 inches along the top edge. Install the next strip with its 2-3 inch overlap and repeat.

Pro Tip: Dealing with Existing Ridge Caps

If you are retrofitting a zinc strip onto an old metal roof, you must remove the existing ridge cap. This changes everything. This may also involve removing old roof material and cleaning up paint spills before re-roofing. A clean, prepared surface helps with proper sealing and long-term durability.

You must carefully un-screw each section without damaging the panels underneath. The old sealant will fight you. Bent ridge caps are hard to re-use.

In my crew’s experience, this retrofit scenario is where DIY projects most often go wrong and cause leaks. It involves deconstructing a finished, sealed system. If your roof already has its ridge cap on, consider this a strong reason to hire a professional roofer for the zinc installation.

The Critical Finish: How to Properly Close and Seal the Ridge

You have the zinc strip installed. Now comes the waterproofing climax of the whole job. How you close the ridge on a metal roof is the difference between a decades of dry protection and a frustrating, expensive leak. One mistake here can undo all your careful work.

Step 1: Install Closure Strips Along Both Sides of the Ridge

Do you need closure strips for metal roofing? The answer is a firm yes. Think of them as the weatherstripping for your roof’s peak.

Take your foam closure strips and press them firmly onto the high rib of the metal panels, running along both sides of the ridge peak. They should snap or press into the corrugation profile snugly.

Their job is simple but vital: they fill the open gaps in the panel ribs, blocking wind-driven rain and pests while still letting the metal expand and contract with temperature changes. Skipping them is an open invitation for water and bugs.

Step 2: Set and Fasten the Ridge Cap

Now, lift your ridge cap panel into place. It should sit centered over the ridge, covering the zinc strip and resting on the closure strips. This technique is different from installing shingles on a hip roof.

Fastening is where leaks are often made. You must drive your screws into the high rib of the roof panel, not the flat area. Every screw needs a sealant washer. Drive them straight down, snug but not so tight you crush the washer or distort the metal.

A straight, clear line of fasteners along both sides of the ridge cap isn’t just for looks; it’s the mark of a sealed, secure installation. If the fasteners are placed over any overlapping sections of the corrugated roofing, it could lead to leaks. Crooked or missed ribs create weak spots.

Step 3: Seal the Ends and Overlaps

Fasteners are not enough. You must think like water. Water finds the lowest point and the smallest gap. The biggest leak points are the ends of the ridge cap and where two ridge cap sections overlap.

Before you snap the final pieces together, apply a generous bead of high-quality, roof-grade polyurethane or silicone sealant under all end laps. Do the same at both gable ends where the ridge cap terminates at the gable roof.

Wipe away any excess with a putty knife for a clean, weather-tight bead that seals without looking messy. This bead is your final, proactive defense against leaks.

The Final Touch: Trimming and Inspection

Once everything is fastened and sealed, trim any overhanging closure strip material with a utility knife for a neat finish.

Then, get on your hands and knees. Inspect every single fastener to ensure the washer is properly seated and not pinched. Run your eyes along every bead of sealant. Look for gaps or thin spots. This ten-minute crawl is your best insurance before you climb down.

After the Install: Care, Limitations, and When to Call a Pro

Realistic Maintenance and What to Expect

Maintenance is straightforward. Once a year, maybe when you clean your gutters, clear any leaves or pine needles from the ridge line. You want rainwater to flow freely over the zinc.

Zinc needs rain to wash its protective particles down the roof, so in very dry climates, its effect can be slower. It’s a passive system, not an instant cleaner.

Can you install zinc strips on flat roofs? No. They require consistent water runoff down a slope to function. On a flat roof, the zinc ions just pool and stain.

When This DIY Project Isn’t for You

Be honest with yourself about the scope. This DIY project is for a simple gable roof. You should not try this if you are unfamiliar with gable roof design and construction principles.

• Your roof has multiple hips, valleys, or dormers.
• The pitch is steeper than 8/12 (it’s dangerously steep).
• There’s existing rust, corrosion, or damage near the ridge.
• You lack proper fall protection, a stable ladder, and solid roofing shoes.

Installing on a standing seam roof is also a different, more specialized process than on an exposed fastener roof. If you’re unsure, you’re not ready.

Calling a professional roofer isn’t a failure; it’s a smart investment in safety, local building code compliance, and a workmanship guarantee. A pro gets it right the first time, so you never have to think about it again.

Common Questions

1. Is Zinc or Copper Better for Stopping Moss?

Zinc is more cost-effective and leaves less noticeable staining, making it a great choice for most homeowners. Copper is slightly more effective and longer-lasting, but comes at a higher premium and can stain light-colored roofs green.

2. How Can I Tell If My Ridge Closure is Failing?

Look for daylight visible in your attic at the ridge, or signs of pests, dust, or water stains on the rafters. From the outside, check for gaps under the ridge cap or sections that have lifted in high winds.

3. What If My Roof is Low-Pitch or I Can’t Use a Strip?

For very low slopes where zinc won’t wash effectively, use a liquid-applied zinc solution sprayed onto the roof surface. Always ensure your ridge is properly sealed first, as this is your primary defense against leaks, not the moss prevention.

Finishing Strong: A Lasting Seal for Your Roof

Getting the zinc strip seated correctly and the ridge cap sealed tightly is what prevents leaks and stops moss for good. I always tell my crew that an hour of careful work here saves days of repair later.

Your roof is a critical shield for your entire property, so make safety your first tool for any inspection or touch-up. Keep building your knowledge with reliable guides on roof care and safety practices for all types of roofs to protect your investment.