Mastic sealant stops moisture

Mastic sealants: Strong, flexible, waterproof

If you’ve never used mastic sealant, you need to read up on it in our short how-to. It’s great for kitchens, bathrooms, windows, and more. You’ll be amazed at how useful this versatile product can be.

What is mastic sealant?

Mastic sealants stay flexible when cured so they’re excellent for applications where movement, vibration, or expansion/contraction is likely. Mastic sealants also adhere to most common building materials like wood, aluminium, glass, marble, brick, and most metals. Its waterproof and elastic nature makes mastic sealant perfect for sealing around windows and doors, bathtubs, sinks, and even roofing applications.

How to use silicone mastic sealant

Mastic sealant is used like any other sealant - just follow the simple steps below:

  1. Ensure the area to be sealed is clean and free of dirt, grease, or old sealant.
  2. Place the tube into the caulk gun and cut the nozzle end of the tube so that it dispenses the right-width bead of sealant.
  3. Squeeze the trigger evenly as you apply a bead of mastic sealant along the gap or seam you’re filling.
  4. Use a sealant tool or your finger (with a nitrile glove) to smooth out and seal the sealant to the surface.
  5. Wipe away any extra sealant or drips with a damp rag and allow the sealant to fully dry before use.

A sealant tool is simply a tool with a rubber end shaped to a rounded 90-degree angle. After you dispense a bead of sealant, use a sealing tool to smooth out the sealant and seal the edges of the bead. It’ll produce a more uniform look than a finger or a rag will… and it’s not as messy!

Using exterior mastic sealant and marine mastic sealant

Here are some things to consider when choosing a mastic sealant for exterior use or a marine mastic sealant. You’ll need to choose an exterior grade, but make sure it’s UV light resistant as well as temperature resistant because exterior applications are subject to higher fluctuations in temperature than just the air temperature. Metal surfaces in sunlight, for example, can easily reach 65°C or more. With such temperature fluctuations, a flexible mastic sealant that can expand and contract will help prevent cracking and leaks!

If using mastic sealant in a marine setting, make sure it’s rated for saltwater use if it’s to be used in or near the ocean. Saltwater puts extra stress on many materials, so the sealant you choose will need to be rated for use in that environment.

Alternatives to mastic sealant

If you just need to do a quick repair, here’s a very convenient alternative to mastic sealant: Loctite Clear Silicone Waterproof Sealant. It has most of the advantages as mastic sealants but comes in a convenient squeeze bottle for quick fixes. It can be used indoors or out to create a strong waterproof bond on glass, ceramic, porcelain, fiberglass, tile, and many other surfaces. It won’t crack, peel, or shrink, and will stay flexible to resist movement and impact.