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How to caulk your roof with the best roof sealants

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A ceiling drip can be a stressful sight, but the right roof sealant will help you caulk your roof so you can relax again. In this guide, we explain how to find leaks and properly seal them.

Roof in a rain storm
Using roof leak repair sealant to ensure your roof is in top condition can prevent leaks and water damage.


Finding the source of a roof leak can be challenging, but it is vital. Roof sealant is the best solution for small- to mid-sized applications for diverting water or plugging holes and cracks; large damaged areas may require a more complex repair.

First, assess where the leak is located in your home. Remember, water may travel from a different location depending on the architecture and structure of your home. Once you have an idea of where the leak is coming from, the safest option is to go up into your attic space. Look for black areas or mold because they are typically strong indicators of water leaks. Go outside and check the shingles/roofing in that area. In flat sections of roof, keep an eye out for misplaced shingles, standing water, mold buildup, or rot. The most common type of roof leak is caused by an object that penetrates the roof, such as your chimney, roof vents, or anything else that passes directly through the roof.

Small gaps and holes caused by objects penetrating the roof can be repaired easily with Loctite PL Roof and Flashing Polyurethane Sealant.


After you have identified the source of a small or medium-sized leak, you can begin filling it with roof leak sealant. For larger repairs, you can use your roof sealant on new joints and materials as needed. Before application, ensure that the joint you wish to apply roof sealant to is dry, clean, and free of any debris. It should also be structurally sound. Although roof leak sealants are flexible, they are not intended to serve as adhesives. If you need to bond wood on your roof, consider using Loctite PL Premium Max.

Steps for caulking your roof with roof sealant are as follows:

  1. Gather the required tools – You will need a razor blade, gloves, a caulking gun, and roof sealant.
  2. Ensure the area is in good condition and there is no rot – Replace all rotting wood with new material.
  3. Identify the problem – Look for tears and cracks in existing roof sealant, because this is normally the cause of roof leaks.
  4. Clean the area – Ensure that the area is free of old caulk, moisture, loose particles, asphalt, tar, paint, wax, and rust. Use a razor blade and acetone spray to remove the old roof sealant. Wear gloves to protect your hands.
  5. Surface preparation – While Loctite PL Roof and Flashing Polyurethane Sealant is generally considered a non-priming sealant, special circumstances or substrates (copper, galvanized and stainless steel) may require a primer. Where incidental water immersion may occur, priming is required. Apply the primer with a brush and allow it to dry for 30 minutes; you typically need only a thin layer. You must apply the primer and roof leak sealant on the same day.
  6. Application – It is important to apply the roof leak sealant with a steady pressure, forcing it into the joint. Protect open products and tools from direct sunlight for the best results. Use roof leak repair sealant together with a backer rod for joints deeper than ½ inch. The depth of the roof sealant should be half the width of the joint. The maximum depth is ½ inch, and the minimum is ¼ inch. Loctite PL Roof and Flashing Polyurethane Sealant will harden within 24 hours, is functional within 3 days, and will fully cure in 7 days.

Choosing the best roof sealant for your project

Selecting the right roof leak sealant for the job is critical. You must select a roof sealant that is specially formulated to withstand harsh weather conditions so you can rest assured it will protect your roof after you have carried out your repair. Elements such as rain, ice, and sunlight can wreak havoc on exterior roof joints and surfaces.

Furthermore, structures shift and flex over time, which means it’s important to have a roof sealant that can do the same. Loctite PL Roof and Flashing Polyurethane Sealant is specially formulated to flex and move with your roof, so it will not tear or rip. On top of that, it is made to stand strong in harsh weather conditions and provide long-term protection. This makes it the ideal roof sealant for heavy duty outdoor projects.

Roof sealant being used to caulk a roof
Choosing the best roof sealant for your project can prolong the life of your roof and prevent water damage.

Products used

  • loctite pl premium max 9oz cartridge
    Loctite PL Premium Max

    Strongest bond to most materials. Ideal for any project where long term strength and durability are a must.

  • loctite pl roof flashing 10oz cartridge
    Loctite PL Roof & Flash

    Sealing roof flashing around skylights, windows, chimneys and roof edging.

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