A leaking roof is the homeowner’s worst nightmare. It immediately reminds you of water intrusion issues like foundation damage and damage to walls and ceilings. Above all, leaky roofs are expensive to repair.
Fortunately, caulking cures many roof system leaks, especially minor gaps and cracks. It’s also cost-effective.
But do you know how to caulk a roof? This guide covers everything you need to know about basic roof caulking, including the best caulk sealants.
What kind of caulk to use on a metal roof?
Silicone sealants are the best choice for metal roof caulking. They adhere strongly to metal surfaces and other construction materials. Moreover, silicone sealants are UV-resistant and offer a weather-tight seal. They are also highly flexible and thus easily withstand natural movement due to expansion and contraction.
Best Caulk Sealants for Metal Roofing
Loctite PL S30, Gorilla Waterproof Patch & Seal Tape, and LR Liquid Rubber Peel & Stick Seam Tape are the most effective caulk sealant options for metal roofs, though Tite Bond and Nova Flex offer a few excellent products too. Here’s what to know about each;
Loctite PL S30 Black Roof and Flashing Sealant
Loctite PL S30 is a flexible sealing material designed specifically for sealing roof flashing. It’s a gun caulking sealant that easily accesses gaps created by damaged flashing. Moreover, the polyurethane sealant is moistureproof and extremely durable.
Gorilla Waterproof Patch & Seal Tape
Gorilla Waterproof Patch & Seal Tape is the go-to sealant for repairing minor roof sections. The 10-foot sealant roll creates a permanent bond that instantly stops leaks.
Apply it during dry, warm weather for the best results. However, it’s equally effective when applied in humid or wet weather.
LR Liquid Rubber Color Waterproof Sealant
Liquid Rubber (LR) has some of the best metal roof sealants. However, the color sealant is best for whole-roof or relatively large sealing projects. It’s a water-based sealant applied using a paint roller or brush.
Alternatively, you can spray it on. It dries to a thin rubber coat, providing maximum weather protection.
Titebond Metal Roof Sealant
Titebond Metal Roof Sealant is a favorite and one of the most common building materials. It offers unbeatable adhesion on painted and unpainted roofs and remains flexible throughout.
More importantly, it holds a weather-tight bond that’s not affected by roof contraction or expansion. The cherry on top is that it’s among the most affordable roof caulk sealants.
Flex Seal Spray Rubber Sealant Coating
Finally, a spray sealant is recommended for easier application over a large area. If so, Flex Seal Spray Rubber Sealant is the best choice.
It easily seeps into creaks and holes, drying to a waterproof but flexible rubberized coating. In addition, it’s a highly durable coating that you can paint once fully cured.
What is Roof Caulk Sealant?
Roof caulking sealants are weatherproofing products applied to roofs to shield the surface from environmental factors such as rain, snow, and heat.
You can apply caulking sealants over the whole roof during roof installation (recommended for flat roofs) or gaps and leaks during repairs.
Types of Metal Roof Caulking Sealants
There are two main metal roof caulk sealants – tape and tube sealants.
Tube sealants are the go-to product for sealing seams and gaps on metal roofs. However, many professionals swear by butyl tape, especially for temporary fixes. Moreover, butyl tape works better than gun caulking if you intend to screw down the roofing panels.
Let’s take a closer look at each to determine how they work and how to pick the right one for your application.
What is Butyl Tape Sealant?
Butyl tapes are synthetic rubber adhesives developed to take over from natural rubber adhesives. As a result, they are less sensitive to hot temperatures and retain their stickiness throughout cold weather.
Moreover, butyl tape creates an airtight, weatherproof bond on most materials, including metal roofing panels.
How it Works
Butyl tape is a single or double-sided tape composed of butyl rubber – a synthetic product comprising a copolymer of isobutylene and isoprene. It forms a flexible material that doesn’t harden, bleed, or stain.
Butyl tapes are pressed onto the surface to form a strong bond. For instance, in a Z-closure, you apply the tape over the identified area, place another metal on top of the butyl tape, and compress the joint to create a strong bond. It helps to fasten the bond every four inches in the center.
Pros and Cons of Tape Sealant
Butyl tape sealant has many pros and cons, making it suitable for selected metal roofing applications but not others.
Butyl Tape Pros
- It’s extremely versatile
- It securely adheres to most materials
- It doesn’t dry out like other adhesives
- It’s less sensitive to temperature than natural rubber
- It’s more affordable than silicone and acrylic sealants
Butyl Tape Cons
- The tape may peel off in extreme weather conditions.
- Butyl dissolves when exposed to strong solvents like turpentine and gasoline.
- Applying butyl tape to a rough, uneven, or dirty surface is a nightmare.
When to Use Butyl Tapes
- Metal-to-Metal applications if you intend to screw down the joint
- Bottom and z-closures
- Offset cleat systems
When to NOT Use Tape Sealant
- If you don’t intend to fasten the joint
- Applications that don’t involve compression to seal the joint
- In between panel seams (butyl tape is too thick for such applications)
How to Apply Butyl Tape Sealant: Step-By-Step Guide
Roof sealing with butyl tape is easy. However, you must be careful to avoid a weak bond. Here’s a step-by-step guide;
- Chill the tape: Put the butyl tape in the fridge for about 2-3 hours before commencing the project. Though not a critical step, “freezing” makes it easier to work with.
- Clean the surface: Two steps are critical here. First, ensure the surface is clean. Remove debris and sand away rust. Then wipe the surface with a rag. Alternatively, pressure-wash the surface and allow it to dry. Secondly, clean oily or greasy spots with a degreaser.
- Apply it to the surface: Carefully peel away a small section of the tape and apply it to the starting point. Then peel more tape and press it onto the surface until you cover the entire crack or leak.
- Press again to eliminate air bubbles: Butyl tape traps plenty of air bubbles, especially if the surface is dirty or wet. So, run your fingers along the length of the tape once more, pressing down and around the tape to eliminate any bubbles.
- Trim the edges: When satisfied with the project, use scissors to trim the excess tape. Also, trim the excess putty from the tape.
- Allow to cure: Butyl tape sealant cures in 3-4 hours. However, it’s best to let it settle overnight for maximum strength.
What is Gun Caulking Sealant?
Gun caulking sealant comes in a tube loaded onto a caulking gun. Always use the gun per the manufacturer’s instructions.
Gun caulking sealants are made from various materials. Though urethane and silicone products are the most common, various rubber and tri-polymer caulking sealants are available too.
Types of Gun Caulking Sealant
The two main categories of gun caulking sealants are solvent-based and water-based products. Solvent-based sealants, like rubber, polyurethane, and rubber, contain solvents. Meanwhile, water-based sealants, like acrylic and latex, don’t.
The main advantage of a solvent-based sealant is its greater resilience against elements. These sealants can withstand extreme weather conditions (heat and cold).
Also, they last longer. Unfortunately, solvent-based sealants are more expensive, harder to apply, and more difficult to remove. They are also unsafe for humans and the environment. So, you must wear a mask during application.
Meanwhile, water-based sealants are more affordable, emit fewer odors, and are safer for humans. So, you don’t require a mask during application. However, they degrade much faster and thus require frequent reapplication.
Acrylic, polyurethane, silicone, and rubber are metal roofs’ main gun caulking sealants.
- Acrylic sealants: Acrylic sealant products are the most common metal roof sealants as they offer the best balance of UV protection and surface waterproofing without burning a hole in your pocket. Thus, they are particularly common in western and southwestern states where sun damage is the primary roof damage concern. The only downside is that they don’t hold up well against water pooling.
- Polyurethane sealants: Polyurethane is almost the opposite of acrylic. It’s excellent against moisture, rain, and pooling water. However, it’s not a very good UV blocker. Therefore, it works best in northern states where snow and leaks are the biggest roof concerns.
- Silicone sealants: Silicone sealants are hands down the best option whether you live in the north or south. They offer unmatched UV resistance and waterproofing qualities, making them equally suitable for sunny and snowy regions. However, they are the most expensive roof sealants and are out of range for many homeowners.
- Rubber Sealants: Rubber sealants comprise natural rubber, which offers excellent resistance against sun and rain. Also, they create thin films that make them ideal for sealing tiny cracks. However, natural rubber cracks in extreme conditions. So, you may need to replace the sealant sooner.
How they Work
Gun caulking sealants can be one-part or two-part products. Single-component sealants comprise a solitary product, like glue in a tube. You squirt it onto the affected area, wipe the excess, and allow it to dry.
Meanwhile, two-part roof sealants comprise two tubes you must mix to create the glue. The manufacturer indicates the mixing ratios and how long to wait after mixing before using the adhesive.
Curable vs. Non-Curable Sealants
A curable sealant arrives as a paste but dries to a hard substance within a specified period after application.
NovaFlex Metal Roof Sealant is an excellent example. It dries to a hard substance within 48 hours at 75 degrees (Fahrenheit) and 50% relative humidity. Alternatively, it fully hardens at 40 degrees and 50% relative humidity in five days.
On the other hand, non-curable gun caulking sealants don’t harden. Instead, they remain soft throughout. The best example is a hot-melt sealant. It’s a flexible material often used on mechanically seamed metal roofs and remains malleable throughout.
Gun Caulk Color Options
Unlike butyl tape, gun caulking sealant comes in multiple colors to suit every project and every taste. Alternatively, you can opt for a clear sealant to preserve your roof colors.
Pros and Cons of Tube Caulking Sealant
The following are common reasons you should or shouldn’t consider gun caulking sealant for your metal roof.
Tube Caulking Sealant Pros
- It’s more suited to tiny cracks than tape sealant.
- Greater resistance to weather conditions
- Exceptional UV resistance
- It comes in multiple colors to suit your needs.
- Extra durability
Tube Caulking Sealant Cons
- More expensive than tube sealant (per square foot)
- More challenging to use (messy and labor-intensive)
- The sheer number of options makes it easy to choose the wrong sealant
When to Use Caulking Gun for Sealing Metal Roofs
- In between panel seams to prevent a metal roof leak
- At the top of pipe boots
- Metal-to-metal applications where you don’t intend to fasten the joint
- Laps, such as ridge cap laps, sidewall laps, metal flashing, etc
When to NOT Use Caulking Gun Sealant
- In sections where the sealant is exposed to weather elements
- To fix gaps or voids in the roof system
Caulking Metal Roof: How to Apply Gun Caulking Roof Sealant
The following is a step-by-step guide to applying caulk sealant on a metal roof using a caulking gun;
- Prep the work surface: Remove all the existing caulk from the roof surface using a utility knife. Then sweep away the debris, wash the roof, and allow it to dry.
- Load the caulking gun: Use a utility knife to trim the tip of the sealant canister. Then insert the canister into the gun with the tip pointing out.
- Apply the caulk: Position the tip of the canister at 45 degrees to the gap or joint. Then squeeze the gun’s trigger to release the sealant. Continue until you cover the entire leak line. Apply sufficient amounts, keeping in mind that most caulking products shrink when curing.
- Smooth the caulk: Use a flat tool, like the back of a spoon, over the caulked section to push the caulk into the gaps while smoothing out the section. Remember to wipe off the excess caulk.
- Allow it to dry: Metal roof caulking sealants dry to the touch in 30 minutes or less. However, they can take up to a week to fully cure.
Factors to Consider when Choosing the Best Metal Roof Sealant
- Roof properties: The type of metal roof (standing seam, metal shingle, corrugated, metal tile, and metal stale) and roof slope are among the roofing properties that directly impact sealant choice. The slope of the roof matters too.
- Type of project: Sealants and caulking products are used for two main purposes – to protect the roof and for repairs. So, consider your project type before you go shopping. For instance, tape sealants are impractical for whole-roof protection. Similarly, brush-on solvents are ill-suited for minor cracks or gaps around screws.
- Thermal resistance and UV reflectivity: The best sealants have high thermal resistance and UV reflectance. This property prevents sealant damage while keeping your home cooler in the summer.
- Waterproofing properties: All sealants provide some level of water resistance. However, rubber, silicone, and polyurethane provide unmatched waterproofing qualities. So, they’re the best if environments with heavy rains or snow.
- C5M rating: The International Organization for Standardization (ISO) recognizes a C1-C5 rating for sealants and caulking products. C1 products are the least resistant to environmental elements, while C5 products are the most resistant. C5 products are further divided into C5I (industrial) and C5M (Marine). Always aim for C5M sealants, as they’re the most weatherproof.
- Ease of application: Tape sealants are the easiest to apply. It’s as easy as applying painter’s tape. Unfortunately, paste sealants require brushing onto the surface or squirting gently and carefully. Worse still, two-part adhesives require mixing before application.
What Parts of a Metal Roof Need Sealing?
Sealing or caulking is applicable in any metal roof part vulnerable to water intrusion. The sealant weatherproofs the roof, blocking out water and preventing UV damage.
Therefore, common application areas include;
- Joints
- Gaps
- Seams
- Fasteners
- Downspouts
- Metal end laps
- Overlaps
- Gutters
How Much does Metal Roof Sealant Cost?
Whole-roof sealant costs $15 to $30 per gallon, on average. It depends on the type of sealant. Silicone sealants are the most expensive, costing $0.5 to $1.4 per square foot (material only), followed by polyurethane and liquid rubber sealants.
Finally, acrylic sealants are the most affordable. One gallon covers 100 to 150 square feet.
On the other hand, tube sealants cost $6 to $8 per tube. But, again, it depends on the type of sealant and the brand.
Lastly, tape sealant prices mainly depend on the size of the tape. For example, 3/32-inch x 3/8-inch x 45-foot rolls cost $3 to $4 per roll. Meanwhile, a wider 7/8-inch x 3/16-inch x 25-foot roll costs $6 to $8 per roll.
DIY makes sense in most cases if you’re confident in your skills. However, professional installation guarantees the best results.
Professional sealing costs $0.5 to $3.0 per square foot (labor charges only) or a minimum service fee between $150 and $300.
How Long does Metal Roof Sealant Last?
Metal roof sealant lasts 10 to 20 years. So, you can expect your sealant to last 15 years on average. This is about the same length of time as roof paints. Therefore, you can seal your roof during painting and expect it to last until the next repaint job.
However, note that many metal roofs last much longer, most lasting 40 to 70 years. Thus, you may need to severally re-seal the panels over the roof system’s life.
Metal Roof Caulking Tips and Tricks
The following are a few handy tips to properly and safely caulk a metal roof with standard sealants;
- Maintain steady dispensing pressure for an even spread: This applies to gun caulking and squeeze-out tubes.
- Clean the spout with a screw: A plug seems to form in the tip, no matter how careful you are. Fortunately, a narrow screw with aggressive threads removes the dried sealant easily.
- Tape before caulking: Painter’s tape allows you to control caulking lines. Remove the tape after smoothing the caulk.
- Choose the right caulking gun: The best gun isn’t necessarily the most expensive on the rack. Instead, focus on handy features like a cradle over a hook and ratchet action over friction action.
- Push, don’t pull: Caulking works better if you push the gun into the gap rather than dragging it along the opening. It produces a better bond by creating adhesion on both sides of the gap.
- Finishing is vital: You shouldn’t see sealant when looking at the roof from the ground. Otherwise, water will easily penetrate the sealant, damaging it and causing fresh leaks.
- Sealing is a secondary defense system, not the primary one: The first line of defense against roof leaks is the roof. Meanwhile, sealant bridges small gaps and cracks within the panels and along the edges. Thus, sometimes it’s better to replace missing or badly damaged roof sections than merely seal them.
Caulking for Metal Roof FAQs
What’s the Best Sealant for Caulking Metal Roof Seams?
A tube of acrylic latex caulk is the best choice for sealing metal panel seams. First, ensure the color matches your roof. Then load the sealant tube into a gun and apply it along the seams.
Loctite Polyseamseal Acrylic Caulk with Silicone is our preferred choice. It forms a strong, weatherproof seal for maximum durability.
What’s the Best Sealant for Caulking Metal Roof Screws?
Most metal roof sealants, especially tube sealants, are sufficient for sealing around metal roof screws. However, if you’re looking for a product specifically formulated for sealing metal roof screws, you can’t do much better than Albion Engineering B12B30SP Spot-Pro System. It is expensive. But you can count on it for a long time.
What’s the Best Caulking for Metal Roof Panels?
Butyl, polyurethane, and silicone are the most commonly used sealants when caulking metal roof panels. They provide a long life while accommodating normal movement when applied properly.
Apply the sealant on a clean, dry surface and only use enough paste. Most importantly, always follow the manufacturer’s instructions.
Summary
Caulking sealants are the primary means to weatherproof metal roofs. They offer added waterproofing and UV-reflection properties, enhancing the roof’s integrity and prolonging its life.
However, choose the right sealant, as the wrong sealant can wear out fast, leading to fresh roof leaks.