Are you tired of constantly worrying about your roof every time a storm rolls in? Or are you exhausted by the cycle of replacing leaky asphalt shingles every 15 to 20 years? It is a frustration many homeowners face. You spend thousands on a roof, only to see it degrade under the harsh sun or get battered by heavy rains. If you are looking for a permanent solution, you are in the right place.
Metal roofing is rapidly becoming the gold standard for homeowners who want durability and style. The appeal is obvious: a metal roof can last anywhere from 40 to 70 years, which is essentially a lifetime for most of us. It is particularly effective in climates with extreme weather. For example, if you are dealing with the scorching summers in Pakistan, metal roofing reflects a significant amount of solar radiant heat, keeping your home cooler and lowering your energy bills.
By installing directly over your existing shingles, you can cut your demolition costs by nearly 50%. You avoid the mess of tearing off old asphalt, you save on dumpster fees, and you keep tons of waste out of landfills. It is a win-win situation.
Why Install Metal Roofing Over Shingles?
Before we pick up a hammer, it is helpful to understand exactly why this method is gaining so much traction. It isn’t just about taking a shortcut; it is about efficiency and structural benefits. Let’s break down the “why” so you can move forward with confidence.
Massive Cost Savings
The most immediate benefit is financial. When you hire a contractor to replace a roof, a huge chunk of that quote is labor—specifically, the labor required to rip up thousands of pounds of old shingles and haul them away. By choosing to install metal roofing over asphalt shingles, you are skipping that step entirely. You avoid the demo fees, which can run between $2 to $5 per square foot. Your total project cost drops significantly, usually landing in the range of raw material costs plus your own time.
Incredible Durability Boost
Metal is tough. While shingles can crack, curl, or blow off in high winds, metal panels are engineered to resist wind speeds of 140+ mph. They are fire-resistant and impervious to rot and insect damage. Interestingly, leaving the shingles underneath actually serves as an extra layer of insulation and sound-dampening. It creates a buffer that helps deaden the sound of heavy rain, which is a common concern for people switching to metal.
Eco-Friendly Choice
If you are conscious about your environmental footprint, this is a great method. Asphalt shingles are a major contributor to landfill waste. By leaving them in place, you are preventing that waste. Furthermore, the metal panels you install are often made from recycled materials and are 100% recyclable themselves at the end of their long life.
Quick Installation
Time is money. A full tear-off and replacement can leave your home exposed to the elements for days or even weeks, depending on the crew size and weather. Installing over shingles drastically shortens the timeline. A focused DIY team can often finish a standard roof in 1-2 weekends.
Local Considerations
If you are reading this from a region like Lahore, sourcing materials is convenient. You can find high-quality corrugated galvanized metal from markets like Anarkali or specialized hardware zones. The availability of local materials makes this an even more affordable option compared to importing specialized roofing tiles.
Tools and Materials Checklist
Preparation is everything. You do not want to be stuck on top of a roof only to realize you are missing a specific type of screw. Below is a detailed checklist to ensure you have everything ready before you start climbing ladders.
Essential Tools
- Ladder: Ensure it is tall enough to extend 3 feet past the roofline for safe access.
- Tin Snips or Metal Shears: You will need these for cutting panels to fit around vents and valleys. Electric shears are a lifesaver for long cuts.
- Cordless Drill/Impact Driver: You will be driving hundreds, if not thousands, of screws. Have backup batteries charged.
- Chalk Line: This is critical for keeping your screw lines straight and professional-looking.
- Safety Gear: This is non-negotiable. You need a sturdy pair of gloves (metal edges are razor-sharp), safety glasses, and, most importantly, a safety harness and rope system.
- Measuring Tape: A 25-foot tape or longer is best.
Required Materials
- Metal Panels: You can choose between standing seam (hidden fasteners) or corrugated (exposed fasteners). For DIYers, exposed fastener systems (24-29 gauge) are usually easier to install.
- Synthetic Underlayment: Do not use standard felt paper; get a high-quality synthetic barrier.
- Wood Strips (Purlins): Optional but recommended. 1×4 wood strips create a flat grid over the shingles to which the metal is attached.
- Screws: You need roofing screws with neoprene washers. These washers seal the hole as you drive the screw, preventing leaks.
- Ridge Caps and Flashing: For the roof peak and the edges.
- Sealant: A high-grade silicone or polyurethane sealant for gaps.
Estimated Cost Breakdown (Per 1,000 Sq Ft)
Here is a rough estimate of what this might cost you in Pakistani Rupees (PKR), keeping in mind that prices fluctuate based on market rates and steel prices.
Item Quantity (Approx. for 1,000 sq ft)Est. Cost (PKR)
Metal Panels 30 – 35 sheets 150,000
Screws/Fasteners 2,000 pieces 20,000
Synthetic Underlayment 1 large roll 15,000
Flashing/Trim Varies by roof shape 15,000
Total Estimated Cost – ~200,000
Preparation: Is Your Roof Ready?
You cannot just slap metal over any old roof. There are a few checks you must perform to ensure the structure can handle the update.
First, inspect the existing shingles. Most building codes allow for two layers of roofing material. If you already have two layers of shingles on your roof, you generally cannot add a third layer (the metal). You would need to tear off at least one layer. If you only have one layer, you are usually good to go.
Next, walk the roof (carefully) and feel for soft spots. If the plywood decking beneath the shingles is rotted or soft, you absolutely must repair it before covering it. Metal roofing will not fix a structural rot problem; it will just hide it while it gets worse.
Check the roof pitch. Metal roofing works best on a slope. Ideally, you want a pitch of 3:12 or greater (which means the roof rises 3 inches for every 12 inches of length). If your roof is flatter than that, you will need specialized waterproofing to prevent leaks.
Finally, verify your clearance. You need to ensure that adding the height of the metal ribs won’t block any vents or interfere with siding where a second story meets the roof. Ensure you have about 1-2 inches of clearance for ventilation.
7-Step DIY Guide: How to Install Metal Roofing Over Shingles
Now we get to the core of the project. This is your roadmap. Take your time with each step, and prioritize accuracy over speed.
Remove Roof Accessories and Clean the Surface
The first step in how to install metal roofing over shingles is creating a clean slate. While you aren’t removing the shingles, you must remove everything else that protrudes from the roof.
Go over the roof and remove all the old ridge vents, ridge caps, and pipe flashing. If you have old vents that are rusted or damaged, now is the time to replace them. You want the surface to be as flush as possible.
Once the accessories are gone, you need to clean. Use a stiff broom to sweep off all branches, leaves, moss, and loose granules. This is vital because if you leave debris underneath the metal, it can trap moisture or scratch the protective coating on the underside of your new metal panels.
If you find any curled shingles or tabs that are sticking up high, nail them down flat. You want the surface to be as smooth as possible so the metal lies flat.
Install Underlayment and Drip Edge
Many people ask, “Do I really need underlayment if I have shingles?” The answer is yes.
The underlayment acts as a slip sheet. Metal expands and contracts with temperature changes (thermal expansion and contraction). If the metal rubs directly against the granulated surface of the asphalt shingles, the granules will act like sandpaper, wearing through the back of the metal panels and leading to rust and leaks.
Roll out your synthetic underlayment horizontally across the roof. Start at the bottom (the eaves) and work your way up toward the peak. Make sure each row overlaps the one below it by at least 6 inches. This creates a shingling effect that sheds water.
After the underlayment is down, install your drip edge. This is a piece of metal flashing that goes along the bottom edge of the roof (eaves) and the sides (rakes). It guides water away from your fascia boards and into the gutters.
Install Valley Flashing and Starter Strips
The valleys (where two roof slopes meet) are the most critical areas for preventing leaks. You cannot just bend a panel into the valley; it will likely crack or leak.
Install a specialized “W” valley flashing down the center of any valleys. It is best to place a layer of self-adhering ice-and-water shield under this flashing for extra protection.
Next, you may need to install a starter strip along the eaves, depending on the specific metal system you bought. This strip locks the bottom of the first panel in place so the wind can’t lift it. If you are using simple corrugated metal, skip a locking strip, but ensure your overhang is consistent (usually 1 to 2 inches) to direct water into the gutters.
Lay the First Row of Metal Panels
This is the moment of truth. The placement of your first panel dictates how straight the entire roof will be.
Start at the eave on one corner of the roof. Position the first panel so it overhangs the eave by about 1 inch. Crucial: You must ensure this panel is square with the roofline. Don’t just follow the edge of the roof (which might be crooked). Use the 3-4-5 triangle method or measure carefully to ensure the panel is perfectly perpendicular to the eave.
Once positioned, drive your screws. If you are using an exposed fastener system, the screws usually go into the “flat” part of the panel (the valley between the ribs) into the wood deck. Note: Check your manufacturer’s instructions, as some require screwing into the rib.
Space the screws every 12 to 18 inches along the panel. Be careful not to overtighten! You want to spin the washer just until it is snug. If you squash the washer so it bulges out the sides, it will crack and leak over time.
Install Subsequent Rows and Overlaps
With the first panel square and secure, the rest of the job falls into a rhythm.
Place the second panel so it overlaps the edge of the first panel. Most metal roofing profiles are designed with a specific “overlap rib” that fits perfectly over the “underlap rib” of the previous sheet.
Apply a strip of butyl tape sealant along the overlap between the two panels before you screw them down. This provides a watertight seal that prevents water from wicking sideways between the sheets during heavy storms.
Continue across the roof. Every few panels, measure the distance to the roof edge at both the top and bottom of each panel to ensure you aren’t drifting. The panels can fan out slightly, so check your squareness often.
When you encounter a vent pipe or chimney, you will need to cut the panels to fit. Use your tin snips to cut a hole, then install a rubber pipe boot around the pipe to seal the connection.
Add Ridge Caps, Flashing, and Closures
Once all the main panels are installed, you will have a gap at the very peak of the roof where the two sides meet. The ridge cap covers this.
Before laying the cap, install closure strips. These are foam strips cut to the exact profile of your metal panels. They fit between the metal panel and the ridge cap to fill the gaps created by the ribs. Without these, birds, bats, and wind-blown rain will get under your roof.
Lay the ridge cap over the peak (and the closure strips) and screw it down through the ribs of the metal panels. This locks everything together. Do the same for any hip caps if your roof has hips.
Final Inspection and Cleanup
You are almost done, but don’t climb down yet. The final inspection is vital for long-term durability.
Walk the entire roof. Look for any screws that might have been driven in at an angle or missed the wood decking below. Replace or tighten them as needed.
This is the most important cleanup step: When you cut metal or drive screws, you create tiny metal shavings called “swarf.” If you leave these shavings on the roof, they will rust almost immediately, leaving unsightly orange stains on your brand-new roof. Use a soft brush or a blower to remove all metal shavings from the roof surface gently.
Clean out your gutters, as they are likely full of debris from the installation. Finally, if you scratched any panels during the process, use a manufacturer-approved touch-up paint pen to seal the scratch.
Cost Savings and Long-Term Maintenance
By taking the DIY route, you have saved between $3,000 and $7,000, depending on the size of your home. That is money that stays in your pocket rather than going to a contractor’s labor fees.
But the benefits continue. Your new metal roof requires very little maintenance. Unlike shingles, which need to be checked regularly for missing granules or cracks, a metal roof needs a visual inspection once a year.
After the monsoon season or a heavy storm, walk around your house and look up. Ensure the flashings are still tight and that no debris has accumulated in the valleys. Wash the roof down with a garden hose once a year to keep it looking shiny and new.
The Return on Investment (ROI) is fantastic. Between the energy savings from reflecting heat and the lack of repair bills, many homeowners find the roof pays for itself within 7 to 10 years.
Common Mistakes to Avoid When Installing Metal Roofing Over Shingles
Even smart DIYers make mistakes. Here are the top three pitfalls to avoid:
- Skipping the Underlayment: Never install metal directly on shingles. The friction will destroy the metal from the inside out. Always use a slip sheet.
- Wrong Screw Placement: Placing screws in the wrong spot or over-tightening them is the #1 cause of leaks. Remember: Snug, not crushed.
- Ignoring the Pitch: If your roof is flat or has a very low slope, standard screw-down metal roofing will leak. You need a different system for flat roofs.
FAQ: How to Install Metal Roofing Over Shingles
Can I install metal roofing over one layer of shingles?
Yes, absolutely. As long as the existing layer is relatively flat and the decking underneath is secure (no rot), installing over one layer is the standard practice.
How long does metal roofing over shingles last?
A properly installed metal roof can last 50+ years. The shingles beneath do not shorten the metal’s lifespan; in fact, they provide a stable cushion.
Is a permit needed in Pakistan for this type of work?
Generally, for minor renovations, you might not need a permit. Still, it is always wise to check with your local Union Council or housing society bylaws, especially in gated communities like Bahria Town or DHA.
What’s the cost per square foot for DIY?
For a DIY project in Pakistan, you are looking at roughly PKR 800 to 1,200 per square foot for materials, depending on the metal gauge and the quality of the insulation/underlayment you choose.
