If you’re considering installing a metal roof over existing shingles, skipping furring strips might seem like an attractive option to save time and money. However, while this approach is possible, it comes with both advantages and challenges. To make an informed decision, let’s dive into the details and evaluate what works best for your roofing needs.
Table of Contents
Things to Consider Before Skipping Furring Strips
1. Roof Condition and Structural Integrity
Start by conducting a detailed roof inspection. Look for signs of:
- Broken shingles, curling shingles, or sagging.
- Issues with the roof deck, such as rot or moisture damage.
- Overall roof load capacity to ensure it can handle the added weight of a metal roof.
A solid foundation is key to a long-lasting roof, especially if you’re aiming for a 50-year roof.
2. Flat Surface and Telegraphing
Metal roofs, such as corrugated panels or standing seam, need a flat surface for proper installation. Uneven shingles can lead to:
- Telegraphing issues, where the imperfections in the shingles show through the metal panels.
- Oil canning, a visible waviness on the metal surface that reduces the roof’s aesthetic appeal.
To mitigate this, adding a layer of roofing felt, synthetic tar paper, or an ice shield is critical.
3. Ventilation and Thermal Management
Skipping furring strips eliminates the air gap that facilitates ventilation and prevents condensation. Without proper ventilation, your roof is more prone to:
- Moisture buildup, which can lead to mold and rot.
- Higher energy bills due to reduced thermal management and energy efficiency.
Consider investing in attic insulation, thermal breaks, or ensuring adequate air circulation to improve temperature regulation.
4. Waterproofing and Ice Dams
When furring strips are skipped, ensuring proper water movement becomes challenging. Install drip edges, water shields, and reliable underlayments in critical areas such as valleys, chimneys, and eaves to protect against leaks and ice dams during winter.
5. Fastening and Long-Term Ramifications
Without the support of horizontal battens or purlins, metal panels may experience:
- Fastener backout, where screws loosen over time due to expansion and contraction.
- Reduced durability and long-term protection, especially in extreme climates.
Pros of Skipping Furring Strips
Cost Savings
Skipping furring strips is often the cheapest installation method. It reduces labor, material costs, and the overall upfront cost.
Faster Installation
Without the added step of installing furring strips, the process is quicker, making it ideal for projects like barn roofs or remodeling in rural areas.
Environmental Benefits
By avoiding the tear-off of old shingles, you reduce waste and lower your project’s environmental impact.
Cons of Skipping Furring Strips
Increased Noise
Metal roofs installed without furring strips often lack noise insulation, amplifying the sound of rain, hail, or wind. Additional attic insulation can help mitigate this.
Shortened Lifespan
The absence of furring strips can compromise the roof’s lifespan, as moisture and uneven surfaces accelerate wear and tear.
Aesthetic Issues
Uneven shingles can detract from the aesthetic appeal of your roof, causing problems like paint fading, impact dents, or scratch marks on ribbed metal panels.
Water Protection Challenges
Without the air gap provided by furring strips, achieving effective waterproofing becomes more difficult, especially around skylights, dormers, and valleys.
How to Install a Metal Roof Without Furring Strips
If you decide to proceed without furring strips, follow these steps for a reliable installation:
Prepare the Surface
- Repair any broken shingles or sagging areas.
- Ensure the deck is level with proper decking installation to avoid uneven spots.
Apply Underlayments
- Use high-quality underlayments like roofing felt, synthetic tar paper, or ice shields to create a barrier against moisture and condensation.
Secure Fasteners
- Use lead washer nails, screws, or other fasteners with rust-prevention coatings. Proper spacing, such as 24-inch spacing, ensures durability.
Install Metal Panels
- Follow the manufacturer’s specifications for a warranty-proof installation, ensuring panels are tightly secured and aligned.
Add Trim Accessories
- Protect edges with ridge caps, fascia, and other trim accessories to enhance both functionality and aesthetics.
Long-Term Costs and Recommendations
While skipping furring strips can lower your installation cost (e.g., $800–$1,600 for a 3000-square-foot roof), it may lead to higher long-term costs for repairs or replacements. To avoid issues like fastener backout, buckling, or water leaks, consulting a local roofer or professional roofer is highly recommended.
Yes, you can install a metal roof over shingles without furring strips, but it’s not always the best option. The key is balancing upfront costs with long-term protection, energy efficiency, and roofing system durability. If you prioritize functionality and lifespan, consider using furring strips or reinforcing your installation with the proper materials and techniques. For a roof that truly stands the test of time, take the time to weigh your options carefully and always rely on expert advice for optimal results.
