Installing Metal Roofing Over Shingles: A Comprehensive DIY Guide
Installing metal roofing over existing asphalt shingles is a popular choice for homeowners looking for increased durability, energy efficiency, and a modern aesthetic. It’s often more cost-effective than a complete roof tear-off and replacement. However, it’s crucial to understand the process thoroughly to ensure a successful and long-lasting installation. This comprehensive guide will walk you through each step, from assessing your roof’s suitability to the final touches.
Is Installing Metal Roofing Over Shingles Right for You?
Before diving in, it’s essential to determine if your roof is a good candidate for this type of installation. Consider these factors:
* **Roof Condition:** The existing shingle roof must be in reasonably good condition. It should be relatively flat, with no significant sags, rotted areas, or excessive curling. A severely damaged or deteriorated roof will require a complete tear-off.
* **Number of Layers:** Most building codes allow for a maximum of two layers of roofing material. If you already have two layers of shingles, you’ll need to remove them before installing metal roofing.
* **Local Building Codes:** Check your local building codes and regulations regarding installing metal roofing over shingles. Some areas may have specific requirements for underlayment, fastening methods, or ventilation.
* **Weight:** Ensure your roof structure can support the additional weight of the metal roofing. While metal roofing is generally lighter than asphalt shingles, the combined weight of the existing shingles and the metal panels can be significant. Consult with a structural engineer if you have any concerns.
* **Ventilation:** Proper ventilation is crucial to prevent moisture buildup and extend the life of your roof. Installing metal roofing over shingles can sometimes impede airflow. You may need to install additional ventilation systems, such as ridge vents or soffit vents, to ensure adequate airflow.
* **Warranty:** Installing metal roofing over shingles may void the manufacturer’s warranty on the metal roofing. Check with the manufacturer to confirm warranty coverage before proceeding.
If you’re unsure about any of these factors, it’s always best to consult with a qualified roofing contractor.
Materials and Tools You’ll Need
* **Metal Roofing Panels:** Choose the type of metal roofing panel that suits your needs and budget. Options include standing seam, corrugated, and metal shingles. Consider the gauge (thickness) of the metal, the finish (paint or coating), and the warranty.
* **Underlayment:** Use a high-quality synthetic underlayment specifically designed for metal roofing. This will provide an additional layer of protection against moisture and help prevent corrosion.
* **Fasteners:** Use the correct type and size of fasteners recommended by the metal roofing manufacturer. These should be corrosion-resistant and designed for use with metal roofing.
* **Fastener Spacing Guides:** Use this to ensure consistent fastener placement. This typically snaps into place with the metal roofing.
* **Trim and Flashing:** Metal trim and flashing are essential for sealing around edges, valleys, chimneys, and other roof penetrations. Use matching trim and flashing from the same manufacturer as the metal roofing panels.
* **Sealant:** Use a high-quality sealant specifically designed for metal roofing. This will help create a watertight seal around fasteners and trim.
* **Safety Gear:** Wear appropriate safety gear, including a hard hat, safety glasses, work gloves, and slip-resistant shoes. A safety harness and rope are recommended for working on steep roofs.
* **Measuring Tape:** For accurate measurements and layout.
* **Pencil or Marker:** For marking cut lines.
* **Chalk Line:** For creating straight lines.
* **Metal Cutting Shears or Nibbler:** For cutting metal roofing panels. Avoid using abrasive blades, as they can damage the finish.
* **Drill or Impact Driver:** For driving fasteners.
* **Screw Gun with Depth Control:** For precise fastener installation.
* **Hammer:** For installing flashing and trim.
* **Seam Roller (for Standing Seam):** To properly crimp the seams.
* **Ladder:** To access the roof safely.
* **Roof Jacks (for steep slopes):** These provide a temporary foothold to prevent sliding.
* **Broom or Leaf Blower:** For cleaning the roof surface.
* **Caulking Gun:** For applying sealant.
Step-by-Step Installation Guide
Follow these steps carefully to install metal roofing over shingles:
**1. Preparation and Inspection:**
* **Inspect the Existing Roof:** Thoroughly inspect the existing shingle roof for any signs of damage, such as loose, cracked, or missing shingles. Repair or replace any damaged shingles before proceeding.
* **Clean the Roof Surface:** Remove any debris, such as leaves, twigs, and dirt, from the roof surface. Use a broom or leaf blower to ensure a clean and smooth surface.
* **Locate Existing Plumbing Vents:** Identify the placement of the plumbing vents that stick through the roof and measure the diameter of them.
* **Check for Proper Slope:** Ensure the roof has adequate slope for metal roofing. Most metal roofing manufacturers recommend a minimum slope of 3:12 (3 inches of rise for every 12 inches of run). If the slope is too shallow, water can pool on the roof and cause leaks.
**2. Install Underlayment:**
* **Roll Out Underlayment:** Starting at the eaves (bottom edge) of the roof, roll out the synthetic underlayment horizontally. Overlap each layer of underlayment by the amount recommended by the manufacturer (typically 4-6 inches).
* **Secure Underlayment:** Use roofing nails or staples to secure the underlayment to the roof deck. Follow the manufacturer’s instructions for fastener spacing.
* **Overlap at Ridges and Valleys:** At ridges and valleys, overlap the underlayment by at least 12 inches to provide extra protection against water intrusion.
* **Underlayment at Plumbing Vents:** Cut the underlayment to wrap around each plumbing vent and seal it using sealant.
**3. Install Drip Edge:**
* **Install Drip Edge Along Eaves:** Install drip edge along the eaves of the roof. The drip edge should extend slightly over the edge of the roof to direct water away from the fascia board.
* **Install Drip Edge Along Rakes:** Install drip edge along the rakes (sloping edges) of the roof. Overlap the drip edge at the corners for a watertight seal.
* **Fasten Drip Edge:** Use roofing nails or screws to fasten the drip edge to the roof deck. Space the fasteners according to the manufacturer’s instructions.
**4. Install Valley Flashing (if applicable):**
* **Cut Valley Flashing:** Cut the valley flashing to the appropriate length. The flashing should extend at least 12 inches beyond the point where the two roof planes meet.
* **Center Valley Flashing:** Center the valley flashing in the valley and secure it to the roof deck using roofing nails or screws. Space the fasteners according to the manufacturer’s instructions.
* **Seal Edges:** Seal the edges of the valley flashing with roofing sealant to prevent water intrusion.
**5. Install Metal Roofing Panels:**
* **Measure and Cut Panels:** Measure the length of the roof and cut the metal roofing panels to the appropriate size. Use metal cutting shears or a nibbler to avoid damaging the finish.
* **Install First Panel:** Starting at the eaves, install the first metal roofing panel. Align the panel carefully and ensure it is properly positioned.
* **Fasten Panels:** Fasten the metal roofing panels to the roof deck using the correct type and size of fasteners recommended by the manufacturer. Use a screw gun with depth control to avoid over-tightening the fasteners.
* **Overlap Panels:** Overlap each subsequent panel with the previous panel according to the manufacturer’s instructions. This is especially important for standing seam roofs, which are designed to interlock.
* **Continue Installing Panels:** Continue installing metal roofing panels, working your way up the roof. Ensure that each panel is properly aligned and fastened.
* **Fastener Placement:** Adhere to the required spacing, usually by using a fastener spacing guide.
**6. Install Ridge Caps:**
* **Measure and Cut Ridge Caps:** Measure the length of the ridge and cut the ridge caps to the appropriate size.
* **Install Ridge Caps:** Install the ridge caps along the ridge of the roof. Overlap the ridge caps according to the manufacturer’s instructions.
* **Fasten Ridge Caps:** Fasten the ridge caps to the roof deck using roofing nails or screws. Space the fasteners according to the manufacturer’s instructions.
* **Seal End Caps:** Many roofers recommend using flexible sealant on the end caps of the ridge caps to prevent water intrusion.
**7. Install Flashing Around Penetrations:**
* **Chimneys:** Cut and install flashing around chimneys to create a watertight seal. Use a combination of base flashing, counter flashing, and sealant.
* **Plumbing Vents:** Install flashing around plumbing vents. Use pre-made vent flashing or fabricate your own using sheet metal.
* **Skylights:** Install flashing around skylights according to the manufacturer’s instructions. Use a combination of step flashing, head flashing, and sill flashing.
**8. Install Trim:**
* **Gable Trim:** Install gable trim along the gable ends of the roof.
* **Fascia Trim:** Install fascia trim along the fascia board.
* **Rake Trim:** Install rake trim along the rakes of the roof.
* **Fasten Trim:** Fasten the trim to the roof deck using roofing nails or screws. Space the fasteners according to the manufacturer’s instructions.
**9. Seal All Seams and Fasteners:**
* **Inspect All Seams:** Carefully inspect all seams, fasteners, and flashings for any gaps or openings.
* **Apply Sealant:** Apply roofing sealant to any gaps or openings to create a watertight seal.
**10. Clean Up:**
* **Remove Debris:** Remove any debris, such as metal scraps, fasteners, and sealant tubes, from the roof and surrounding area.
* **Dispose of Waste:** Dispose of all waste materials properly.
Tips for a Successful Installation
* **Read the Manufacturer’s Instructions:** Always read and follow the manufacturer’s instructions for the specific metal roofing panels you are using. This will ensure proper installation and help maintain the warranty.
* **Use the Right Tools:** Use the correct tools for the job. Using the wrong tools can damage the metal roofing panels and compromise the installation.
* **Take Your Time:** Don’t rush the installation process. Take your time and pay attention to detail. A rushed installation can lead to mistakes and leaks.
* **Work Safely:** Always prioritize safety when working on a roof. Wear appropriate safety gear and follow safe work practices.
* **Consider Hiring a Professional:** If you are not comfortable working on a roof or if you are unsure about any aspect of the installation process, consider hiring a professional roofing contractor.
* **Ventilation is Key:** Ensure adequate ventilation. Proper ventilation is critical for the lifespan of the roof and to prevent moisture buildup.
* **Use Proper Fasteners:** Choosing the right fastener is crucial. Use only the fasteners recommended by the manufacturer of your roofing panels.
* **Check the Weather Forecast:** Avoid working during inclement weather, such as rain, snow, or high winds.
* **Use Roof Jacks:** Use roof jacks for enhanced safety, particularly on steeper slopes.
* **Keep Panels Clean:** Keep metal roofing panels clean during installation to avoid scratches or damage to the finish.
Advantages of Installing Metal Roofing Over Shingles
* **Cost Savings:** Avoids the cost of tearing off the old roof.
* **Added Insulation:** The existing shingles provide an extra layer of insulation.
* **Noise Reduction:** The shingle layer can help dampen noise from rain or hail.
* **Extended Roof Life:** Metal roofing is known for its longevity.
* **Aesthetic Appeal:** Metal roofing offers a modern and attractive look.
Disadvantages of Installing Metal Roofing Over Shingles
* **Weight Concerns:** Added weight on the roof structure.
* **Potential for Trapped Moisture:** If the existing roof is not properly ventilated, moisture can become trapped and cause problems.
* **Concealed Damage:** Existing damage to the shingles may be hidden and undetected, leading to future issues.
* **Warranty Issues:** Some manufacturers may void the warranty if metal roofing is installed over shingles.
* **Complicated Repairs:** Future repairs can be more complicated as the existing shingles must be considered.
Conclusion
Installing metal roofing over shingles can be a rewarding DIY project that enhances your home’s value and curb appeal. By following these steps and taking the necessary precautions, you can achieve a successful and long-lasting installation. However, it’s crucial to carefully assess your roof’s suitability and consider your own skill level before embarking on this project. If you’re unsure about any aspect of the installation, don’t hesitate to consult with a qualified roofing professional. Remember to always prioritize safety and follow local building codes. A well-installed metal roof will provide decades of protection and beauty for your home.