Asphalt And Metal Roof – Choosing The Best Material For Your Home
Choosing between asphalt shingles and metal roofing depends on your budget, DIY skill level, and long-term goals. Asphalt is more affordable upfront and easier for a solo DIYer to install, while metal offers superior longevity (40-70 years) and energy efficiency.
In many cases, you can install a metal roof directly over existing asphalt shingles using furring strips, which saves on labor and disposal costs. Always check local building codes and ensure your roof structure can handle the weight of both layers.
Choosing a new roof for your home or workshop is one of the most significant investments you will ever make as a property owner. It is the first line of defense against the elements, and the material you choose dictates your maintenance schedule for the next several decades.
Deciding between an asphalt and metal roof is a common dilemma for the modern DIYer looking to balance cost, aesthetics, and durability. This guide will break down everything you need to know to make an informed decision for your specific project needs.
We will explore the technical differences, installation challenges, and the unique benefits each material brings to the table. Whether you are roofing a small garden shed or your primary residence, the following insights will help you work like a pro.
Evaluating the Pros and Cons of an Asphalt and Metal Roof
When you start comparing materials, you have to look beyond the initial price tag and consider the total lifecycle of the system. Asphalt shingles have been the standard for decades because they are universally available and relatively simple to install without specialized heavy equipment.
Traditional shingles are made of a fiberglass mat saturated with asphalt and coated with ceramic granules to reflect UV rays. They are excellent at handling foot traffic and are very easy to repair if a single shingle blows off during a storm.
On the other hand, metal roofing has surged in popularity among DIYers due to its incredible lifespan and modern aesthetic. While the upfront cost is higher, the durability of steel or aluminum often justifies the expense for those planning to stay in their homes long-term.
Durability and Lifespan Comparison
Standard architectural asphalt shingles typically last between 20 and 30 years, depending on the climate and ventilation. In high-heat areas, the asphalt can become brittle over time, leading to granule loss and eventual leaks.
Metal systems are frequently rated for 50 years or more, with many standing-seam options lasting a lifetime. Metal is naturally resistant to fire, rot, and insect damage, making it a “set it and forget it” solution for many homeowners.
If you live in an area prone to wildfires or heavy snow, metal provides a level of protection that asphalt simply cannot match. Snow slides off metal easily, preventing ice dams that often plague shingle roofs in northern climates.
Cost Considerations for the DIYer
From a purely financial standpoint, asphalt is the clear winner for the initial purchase, often costing half as much as a mid-range metal system. This makes it the go-to choice for budget-conscious renovations or quick workshop builds.
However, you must factor in the “cost per year” of the roof’s life, where metal often becomes the cheaper option over 40 years. Metal can also increase your home’s resale value and potentially lower your homeowners insurance premiums in certain regions.
Don’t forget the cost of specialized tools; while you can install shingles with a hammer and a utility knife, metal requires snips and impact drivers. You may also need a metal brake for custom flashing, which can be rented or purchased depending on your project scale.
Understanding the Basics of an Asphalt and Metal Roof System
Before you climb a ladder, you need to understand the anatomy of these two very different roofing systems. An asphalt and metal roof both require a solid deck, but the underlayment and fastening methods differ significantly between them.
Asphalt roofs rely on a “lapping” system where each shingle overlaps the one below it to shed water. It is a gravity-based system that requires a minimum pitch, usually 2:12 or greater, to ensure water doesn’t back up under the tabs.
Metal roofs can be either “exposed fastener” or “hidden fastener” (standing seam) systems, each with its own set of rules. Exposed fastener panels are more DIY-friendly but require periodic maintenance to ensure the rubber washers on the screws haven’t degraded.
The Role of Underlayment
For both materials, the underlayment is your secondary water barrier, and I always recommend a high-quality synthetic underlayment over old-school felt paper. Synthetics are more tear-resistant and provide a safer, non-slip surface for you to walk on during the installation.
When installing metal, you might also consider a “high-temp” underlayment, especially if you are using a dark-colored panel. Metal can get extremely hot in the summer, and standard underlayment can sometimes stick to the metal or degrade under intense heat.
Proper underlayment also helps with “roof noise,” which is a common concern for people switching to metal. A thick, high-quality barrier helps dampen the sound of rain, ensuring your workshop or home stays quiet and comfortable.
Ventilation Requirements
No matter which material you choose, a roof is only as good as its ventilation system to prevent moisture buildup in the attic. Asphalt shingles require consistent airflow to prevent the shingles from “cooking” from the underside, which shortens their life.
Metal roofs also need ventilation, often achieved through a vented ridge cap that allows hot air to escape while keeping out rain. Without proper airflow, condensation can form on the underside of the metal panels, leading to rust or rot in the wooden decking.
Always ensure your soffit vents are clear and that you have a balanced intake and exhaust system. This is a critical step that many DIYers overlook, but it is essential for the long-term health of your structure.
Can You Install Metal Over Existing Asphalt?
One of the biggest advantages of choosing metal is the ability to install it directly over your existing asphalt and metal roof transition. This process, known as a “retrofit,” saves you the back-breaking labor of tearing off old shingles and the cost of disposal.
However, you cannot just screw metal panels directly into the old shingles without some preparation. Most pros recommend using furring strips (1×4 wood boards) ran horizontally across the roof to create a flat, vented plane.
These strips provide a solid anchoring point for your metal screws and create an air gap between the old and new materials. This air gap acts as an insulating layer, helping to keep your home cooler in the summer and warmer in the winter.
Checking for Structural Integrity
Before deciding to go over the top, you must inspect your roof deck for any signs of rot or soft spots. If the existing shingles are curling badly or the wood underneath is soft, a full tear-off is the only safe way to proceed.
Adding a second layer of roofing adds weight to your rafters, though metal is significantly lighter than asphalt. Most modern homes are engineered to handle two layers of roofing, but it is always wise to consult a structural engineer if you have any doubts.
If your current roof already has two layers of asphalt shingles, building codes generally require a full removal before adding anything else. Check your local building department requirements to ensure your project stays up to code and remains legal.
Essential Tools and Materials for Your Roofing Project
To get professional results, you need the right kit; using the wrong tools can lead to leaks or damaged materials. For an asphalt and metal roof project, your tool belt will look a bit different depending on which direction you go.
For asphalt, you’ll need a roofing nailer (air-powered is best), a sharp utility knife with hook blades, and a chalk line. A shingle ripper is also handy if you are doing a tear-off or need to replace a damaged section later on.
Metal installation requires a good impact driver with a depth-sensing nosepiece to avoid over-tightening the fasteners. You will also need aviation snips (left, right, and straight) or a metal nibbler attachment for your drill to make clean cuts.
- Fall Protection: A full body harness and roof anchor are non-negotiable for any height.
- Sealants: Use high-grade butyl tape or specialized roofing silicone for flashing and transitions.
- Fasteners: Use galvanized nails for asphalt and neoprene-washer screws for metal.
- Safety Gear: Cut-resistant gloves are essential when handling sharp metal panels.
I always recommend buying 10% more material than your measurements suggest to account for waste and cutting errors. Having an extra bundle of shingles or a spare metal panel in the garage is a lifesaver if you make a mistake mid-project.
Step-by-Step Guide to a Metal Roof Retrofit
If you have decided to install a metal system over your existing asphalt and metal roof, follow these steps for a clean finish. First, clear the roof of any debris and remove any old ridge caps or bulky flashing that might sit unevenly.
Install your 1×4 furring strips starting at the eave and spacing them according to your metal manufacturer’s specifications (usually 16 or 24 inches). Use 3-inch deck screws to ensure you are biting deep into the rafters, not just the thin plywood decking.
Once your “strapping” is in place, install your drip edge along the eaves to ensure water sheds away from the fascia boards. This is the foundation of your water management system, so take your time to get it straight and level.
- Layout: Square up your first panel carefully; if the first one is crooked, the whole roof will be.
- Fastening: Drive screws into the center of the furring strips, ensuring the rubber washer is compressed but not smashed.
- Overlapping: Follow the manufacturer’s guide for “rib” overlaps to prevent capillary action from pulling water upward.
- Flashing: Install “W” valley flashing and chimney boots using plenty of roofing sealant.
- Ridge Cap: Finish with a vented ridge cap to allow the attic to breathe.
Remember to sweep the roof after you are done to remove any metal shavings (swarf). These tiny bits of metal will rust quickly and can stain your brand-new panels if they aren’t cleared away immediately.
Common Mistakes to Avoid During Installation
Even seasoned DIYers can run into trouble if they rush the process or ignore the “fine print” of roofing. One of the most common errors in metal roofing is over-tightening screws, which crushes the washer and causes it to crack and leak within a few years.
Another mistake is using a circular saw with a standard wood blade to cut metal panels; this generates extreme heat that can ruin the paint finish. Always use a metal-cutting blade or snips to preserve the integrity of the protective coating on your panels.
For asphalt, the most frequent error is “high nailing,” where the nails are driven above the designated nail line. This prevents the nail from catching the shingle underneath, making the roof much more susceptible to wind blow-offs during storms.
Ensure you pay close attention to the “starter strip” at the edge of the roof; this provides the initial seal that keeps the wind from lifting the first row. If you skip the starter course, you are essentially building a roof that is waiting to fail in the next big gust.
Frequently Asked Questions About Asphalt and Metal Roof Options
Is a metal roof much louder than asphalt during a rainstorm?
When installed over a solid deck with proper underlayment and insulation, the sound difference is negligible. Most people find the sound of rain on a metal roof to be quite soothing, and it is rarely louder than the noise coming through your windows.
Can I walk on a metal roof like I can on asphalt?
Yes, but you must be more careful; metal can be extremely slippery when wet or dusty. You should also wear soft-soled shoes and walk on the flat areas of the panels or where the furring strips provide support to avoid denting the ribs.
Which material is better for solar panel installation?
Metal is widely considered the superior choice for solar because you can use “S-5!” clamps that attach to the standing seams. This allows you to mount panels without piercing the roof, whereas asphalt requires drilling holes and using heavy-duty flashing kits.
How do I handle a chimney transition on a metal roof?
Chimneys require custom-bent flashing and a “cricket” to divert water around the back of the structure. This is one of the more advanced carpentry tasks in roofing, so don’t be afraid to consult a local sheet metal shop for custom pieces.
Final Thoughts on Choosing Your Next Roof
Whether you choose the classic reliability of asphalt or the modern endurance of metal, the key to success is in the details of the installation. An asphalt and metal roof can both protect your home for decades if you prioritize safety and follow the manufacturer’s instructions to the letter.
Take the time to measure twice, invest in high-quality underlayment, and never cut corners on your flashing and sealants. Roofing is hard work, but there is an incredible sense of satisfaction and security that comes from knowing your workshop is dry and protected.
If you are still on the fence, start small—try roofing a shed or a wood storage rack first to get a feel for the materials. You’ve got the skills to tackle this project; just take it one square at a time, stay tied off, and build something that lasts!
