How to Install Metal Roofing on A Flat Roof
Metal roofing has become an increasingly popular choice for flat roofs due to its exceptional durability, weather resistance, and energy efficiency. Unlike traditional roofing materials, metal roofing can withstand harsh environmental conditions, such as high winds, heavy rain, and even hail, without compromising its structural integrity.
While it may seem counterintuitive to install metal roofing on a flat roof, modern advancements in material design and installation techniques have made this a viable and preferred option. Dispelling the myth that metal roofs are unsuitable for flat surfaces, manufacturers now offer specialized metal roofing systems designed specifically for low-slope or flat roof applications.
However, it’s crucial to note that installing metal roofing on a flat roof is a complex process that requires careful planning, adherence to safety protocols, and compliance with local building codes and regulations.
How to Prepare Your Roof for Metal Roofing Installation
Measure the Roof Area
Accurately measure the length and width of your flat roof, including any protrusions like HVAC units. For example, if your roof is 40 ft x 30 ft, the area is 1,200 sq ft.
Most metal roofing panels are 16 or 20 inches wide with a 1-inch overlap. Let’s assume 20-inch panels:
- 1,200 sq ft / (20 in / 12 in/ft) = 720 linear feet of panels needed
- Add 10% for waste and cutting: 720 linear feet x 1.1 = 792 linear feet of panels
Inspect and Prepare the Roof Deck
Ensure the roof deck is solid, clean, and level. Replace any rotted or damaged sections. Cover the deck with an underlayment like Grace Ultra membrane to prevent leaks.
Gather Materials
For this part, let’s assume the roof is a 1,200 sq ft roof with 792 linear feet of 20-inch steel panels. Therefore, you’ll need:
- 792 linear feet of 26-gauge steel interlocking panels ($4-$6/linear ft) = $3,168 – $4,752
- 15 rolls of underlayment membrane ($50/roll) = $750
- Closures, drip edges, sealant, and fasteners = $500
- Total Materials Cost: Approximately $4,400 – $6,000
- Rent/buy tools like power shears ($80 rental), nibblers ($250), drills, and safety gear.
How to Install Metal Roofing on A Flat Roof
Install Underlayment and Flashing
Start by rolling out the underlayment horizontally across the roof deck. Use a minimum 6-inch overlap at the seams and secure with cap nails every 6 inches.
Install drip edge flashing along roof perimeters, overlapping the underlayment by 3 inches up the deck.
Flash all roof penetrations like pipes or HVAC units using standard flat roof flashing techniques.
Layout and Install Metal Panels
Start installing panels from one side, laying them perpendicular to the slope direction. Use a chalk line to ensure panels are straight.
Overlap panels using the manufacturer’s interlocking method. Typically you crimp or snap the male/female edges together using seamers or crimp tools.
Fix the leading edge of each panel to the deck using #10 wood screws every 8-12 inches.
Stagger the panel end laps by at least 2 feet. Install closure strips over the end laps and seal with butyl tape or roofing caulk.
Trim and Finish
Trim panel ends and side edges using metal snips or nibblers. Leave 1/2 inch for expansion/contraction.
Install matching color screws in the flat area every 16-20 inches to secure panels fully.
Finally, caulk all edges, screws, closures, and seams for a weathertight seal.
How Much Does Metal Roofing Cost
For the 1,200 sq ft example roof:
- Materials: $4,400 – $6,000
- Tools: $300-$500 rental or purchase
- Permits: $100-$500
- Total DIY Cost: Approximately $5,000 – $7,000
Professional Installation Cost: $10,000 – $15,000+ for labor and materials. Higher costs account for overhead, profit, and warranty.
Hire a pro for complex roofs or if you lack roofing experience. Get multiple quotes, and verify licensing, insurance, and warranties.
Summary
Remember, safety should always be the top priority throughout the process. Comply with local building codes, obtain necessary permits, and consider hiring experienced professionals for complex installations or if you lack the required expertise.
The benefits of a well-installed metal roof are numerous, including resistance to severe weather conditions, energy savings, and minimal maintenance requirements. With proper care and maintenance, your metal roof can provide decades of reliable protection for your home or commercial building.
FAQs
Can any type of metal roofing be installed on a flat roof?
No, not all metal roofing materials are suitable for flat roof applications. Specialized systems, such as standing seam panels, metal shingles, or composite panels designed specifically for low-slope or flat roofs, should be used. Traditional residential metal roofing materials may not provide adequate water drainage or meet the necessary installation requirements for flat surfaces.
Is metal roofing for flat roofs more expensive than traditional roofing materials?
The initial cost of metal roofing for flat roofs can be higher compared to some traditional roofing materials. However, metal roofs often have a longer lifespan, require less maintenance, and offer better energy efficiency, which can offset the initial investment over time.
Can I install a metal roof on a flat roof myself, or should I hire a professional?
While it’s possible to install a metal roof on a flat roof as a DIY project, it’s generally recommended to hire a professional roofing contractor, especially for larger or more complex installations. Professional contractors have the necessary expertise, specialized equipment, and safety protocols to ensure a proper and secure installation.
How long does a metal roof on a flat roof typically last?
With proper installation and maintenance, metal roofs on flat roofs can last anywhere from 40 to 70 years, depending on the specific material and climate conditions. High-quality steel or aluminum roofs can potentially last even longer with regular care and maintenance.
