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You can do it! How to caulk windows

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Caulking windows properly can protect your house from moisture, air leaks, and extremely hot and cold temperatures. Sealing up panes, trim, and sills takes a bit of skill and expertise, but it doesn’t have to be a headache. Read on for everything you need to know to seal your windows using basic caulking techniques.

Caulking windows
Caulking window panes, sills, and trim is critical to protecting your house against tough weather.

Caulking windows: The basics

Caulking your home’s windows is an important step in keeping your home comfortable and making it energy efficient. Sealing windows prevents air leaks and keeps out moisture, which reduces the amount of heating or air conditioning needed. That means lower utility costs and a smaller household carbon footprint.

Learning how to caulk windows isn’t tricky, and it can really help weatherize your home. Here are the basics, so you can start caulking and make the most of your windows.

Window caulking: Interior and exterior caulking

Starting with the right tools is an important step in caulking windows. A good caulking gun is essential to every home repair toolkit. Caulking guns can be found at hardware stores and are used to load the caulk cartridge and apply caulk. Look for a smooth-rod, dripless caulk gun that has a spring-loaded mechanism to deliver even pressure with minimal force. This prevents messy excess caulk and ensures even, consistent application.

The first decision you need to make when caulking both interior and exterior windows is what type of caulk to use. Generally, caulk comes in a few basic types: acrylic latex, siliconized latex, silicone, and polyurethane.

Acrylic latex caulk is water-based, which means fewer hazardous chemical ingredients and easy clean-up. While not particularly weather- or temperature-resistant, acrylic latex can be painted or purchased pre-tinted to complement existing color schemes. It is best suited for interior applications.

Siliconized latex is similar to acrylic latex but contains silanes, a type of silicone. It has many of the same properties as acrylic latex but has greater resistance to weather and creates more durable bonds. This makes siliconized latex a good choice for exterior window caulking.

Silicone caulk is highly resilient against temperature and mildew, making it suitable for kitchen, bath, and HVAC applications. It comes in acid-cure and neutral-cure varieties. Acid-cure works best for non-porous materials like glass. Neutral-cure is better for wood, metal, or plastic, as well as common materials such as vinyl siding. Silicone is highly waterproof, which is great for tubs and sinks.

Polyurethane caulks are solvent-based, not water-based, which makes them quite powerful. It can be a bit more challenging to work with them than with silicone caulks. Polyurethane caulks work well for bonding most common housing materials but can break down over time when exposed to UV radiation.

Silane-modified polymers (SMPs) are excellent adhesives for use on almost all substrates, combining properties of silicones and polyurethanes. Try an SMP glue for a powerful, elastic bond on windows that dries clear and resists weather, dirt, UV radiation, and dust

Caulking interior window
Interior window caulking can be simple with the right materials and a bit of DIY finesse.

How to fix a broken window seal

Window seals typically develop breaks or leaks at points of contact: where one section of the windows meets another, where the window meets the frame, or where the frame meets the wall. Luckily, fixing window seals is easy.

Begin by scraping away loose glazing and old caulk. Use a spray-on commercial caulk softener if necessary; let it soak in for a couple hours, then strip away the loose caulk with a putty knife or caulk removal tool. Clean away as much of the old caulk as possible to allow the new coat to form a strong hold. Also, ensure that any sealant remover residue is gone before applying new sealant – otherwise it could hamper or even prevent the sealant’s adhesion. Keep in mind: Some caulk removers require treatment with special chemicals to remove their residues. Check the manufacturer’s instructions if in doubt.

You may need to install new glazing on the window. You can spread along the base of the window pane to create a compact seal. Paint as necessary and let it dry according to the product instructions.

Apply new caulk once the area is clean and dry. Load your caulk cartridge into the caulking gun and open the tube. If you need a versatile, all-purpose sealant with superior adhesion, low odors, weather resistance, and unbeatable sealing strength, we recommend Loctite PL Heavy Duty Sealant. It is perfect for caulking windows and many other applications.

Apply the caulk along the seam with steady pressure in a smooth motion. Use a wet finger or cloth to smooth out the caulk. You may want to use masking tape before applying the caulk to help create a crisp line and protect adjacent areas.

Let the caulk dry undisturbed for 12 to 15 hours. Your window seal should now be airtight.

Check out this video to learn more about Loctite PL Heavy Duty Sealant:

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Broken window
Learn how to caulk a window seal and keep out nasty drafts and leaks.

How to caulk window trim

Caulking window trim involves many of the same steps as caulking a broken window seam, but it requires a bit more care to ensure your windows stay looking great.

For interior window trim, use an acrylic latex caulk. Loctite Polyseamseal Acrylic Caulk with Silicone is a high-quality acrylic caulk with added silicone for durability and adhesion. It sets quickly and can be painted within 30 minutes. It’s a perfect caulk for sealing gaps around frames, baseboards, trim, and molding, and it bonds with superior hold to wood, drywall, plaster, metals, brick, concrete, masonry, and painted surfaces.

Window trim and caulking gun
Sealing window trim tight can help keep your house warm and your utility bills low.

How to caulk window sills and frames

Caulking outdoor window sills and frames requires a product that will hold up to harsh weather conditions. Your best choice is Loctite PL Window Door & Siding Polyurethane Sealant because it forms permanent, water- and weather-resistant seals in most exterior gaps and joints. It is durable, flexible, and resistant to UV radiation and ozone, making it ideal for caulking windows and other demanding outdoor applications.

Leaky window sill
Caulk those leaky window sills and frames with a strong polyurethane sealant to avoid damage from moisture or temperature.

Products used

  • loctite pl window door siding white 10oz cartridge
    Loctite PL Window, Door & Siding

    Forming commercial grade seals. Permanent water and weather resistant.

  • loctite polyseamseal acws white 10oz cartridge
    Loctite Polyseamseal ACWS

    Provides a flexible, weather resistant seal. Paintable in 30 minutes.

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