Pros and Cons to Mastic Sealant

applying sealant to amber-colored ceramic tile

A mastic sealant is a type of liquid sealant that cures in an elastic state, thus making it flexible while holding the bond of the surfaces that has attached together. It adheres to just about any material making an all-purpose type of sealant. Wood, aluminum, glass, marble, and even duct board are all standard applications for mastic sealant. Most contractors use mastic sealant to connect windows to structures. Cracks around bathtubs and many types of masonry can be sealed with mastic sealant as well. Roofing and brick structures respond well to mastic sealants, and even vehicles such as cars and boats incorporate mastic sealants to create a dust free surface. The life of mastic sealants is usually about five years before reapplication is required to ensure continued efficiency.


glove, sealant, and other home improvement supplies

  1. One positive characteristic of mastic sealant is that it has a very smooth exterior while keeping its rigid form underneath.
  2. Surfaces do not have to be primed when using this type of sealant, and although applied thick, it adheres smoothly to any surface. It is important that the area to be joined or sealed be clean and dry, just like any other sealant on the market.
  3. Mastic sealant may be used outdoors as well because of its waterproof quality. It can be applied on rain duct leaks outdoors, for example.
  4. It is also favored for areas under high or low temperatures such as heater vents or drier vents and contains ultraviolet inhibitors to make sure that it is protected from damaging effects of the sun that will often weaken other types of sealants. That makes it a good choice for use on roofs, or any surface that is constantly exposed to sunlight. Most mastic sealants will also work well with metal because they do not corrode over time.
  5. Also, because of the mastic sealant’s flexible quality, it functions well in areas with mild vibration and heat, like heating ducts.


sealing a window with silicone

  1. Mastic sealant is not recommended for areas that have too much joint movement, or anything that will be moved a long length.

  2. It works well with constant pressure on it, but not constant movement.

  3. It also works best when applied thickly and is not recommended if only a thin layer is needed such as touch ups. Another sealant is a better choice for those types of repairs.