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Mind the gap!

Learn how to caulk large gaps in anything

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There’s not one simple answer for learning how to caulk large gaps. Gaps come in all shapes and sizes and need to be treated individually. We’ll take you through some different scenarios and point out the products that best fit each job.

How to choose the right material for caulking large gaps

Proper gap sealing is an important part of any project, as it helps preserve the health of the structure. But what happens when you come across gaps that are too big for a simple bead of sealant?  

Before caking on layer after layer of caulking material, stop and consider the space you’re working with. The strategy for covering large gaps in bathrooms, differs from the strategy for windows or concrete. Here we’ve listed different scenarios where you might be faced with caulking large gaps, and how to best accomplish it.

How to caulk big gaps in kitchens and bathrooms

Silicone sealants are most used in kitchens and baths because of their flexibility and water resistance. However, doubling up on sealant to fill a large gap is problematic, as it leaves uneven surfaces, shrinks after drying and can be prone to cracking.

For large gaps in kitchens or baths, use a backer rod to fill the gap before applying joint sealant. Backer rods fill the space and reduce the amount of sealant needed to fill the joint. They come in a variety of shapes and sizes, so measure the width of the joint and follow the recommended ratio size when purchasing. Here’s what you need, and how to caulk large gaps with the help of a backer rod.


  • sealant caulk and caulk gun
  • backer rod
  • smoothing tool
  • cleaning rags

How to:

  1. Insert the backer rod into the gap and compress the rod into the joint until it’s the same level as the surface.
  2. Apply a layer of sealant bead over the joint.
  3. Smooth the caulk with the tool. 
  4. Wipe away excess residue with a damp cloth.

How to caulk big gaps: Insulating with Tite Foam

Tite Foam is specifically designed to fill and seal up large gaps on a variety of different materials and spaces. This versatile filling foam can be used on interiors or exteriors, is sandable, paintable, and provides a quick and reliable seal against the elements.

While the application process is the same for all Loctite Tite Foams, there are different formulations catering to different projects.

Tite Foam Application:

  1. Prep the can according to the graph.
  2. Holding the can upside down, dispense the foam, only filling the joint by half to avoid overflow.
  3. Shake the can regularly during application process.
  4. Allow foam to cure for 1 hour before trimming or sanding.
  5. Add a topcoat of paint, plaster, mortar, etc. after the full cure time has been achieved.

How to caulk large gaps in metal and stone

For caulking and filling large exterior gaps in concrete and other masonry, Loctite PL Concrete Non-Sag Polyurethane Sealant is the answer. This elastic sealant has a recommended maximum joint width of 1.5 inches (38mm) and expands and contracts with the elements to resist tears and breaks. Its non-sag formula allows you to fill large gaps and cracks in vertical and horizontal surfaces, without a drippy mess. As a bonus, it has a textured appearance that blends with other masonry materials and can be painted.

Application tips for filling deep joints:

  1. Read the complete manufacturer’s instructions about surface preparation and application before proceeding. Different surfaces require specific preparation.
  2. For deep joints, insert a closed-cell backer-rod or expansion joint filler. Make sure the backing material is tight to the sides of the joint to prevent sealant loss through the bottom.
  3. Begin filling joints from the bottom. Apply the caulk in a steady stream, avoiding bridging of the joint which causes air bubbles. Sealant will self-level to form an even joint surface.

Products used

  • Loctite Epoxy Metal Concrete syringe FOP RGB
    Loctite Epoxy Metal & Concrete

    Anchoring bolts, railings and general repair of concrete, stone and cinderblock.

  • loctite pl concrete non sag 10oz cartridge
    Loctite PL Non-Sag Concrete

    Forming water and weatherproof seals in all exterior concrete and masonry gaps and joints.

  • loctite tite foam big gaps 12oz can
    Loctite Tite Foam Big Gaps

    Seal and insulate gaps & cracks up to 3” inside or out

  • loctite tite foam gaps cracks 12oz can
    Loctite Tite Foam Gaps & Cracks

    Seal and insulate gaps & cracks up to 1” inside or out

  • loctite tite foam window door 12oz can
    Loctite Tite Foam Window & Door

    Specialized formula will not bow windows or doors

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