Mastic is the sealant used in expansion joints. There are different types of mastic but the most common is elastomeric polyurethane. Between the coping and deck of a pool
Throughout pool decks and concrete driveways
Around fire pits, BBQ’s, homes, etc. How do I know if I need mastic? If you just installed concrete you will see foam in the joints between the concrete slabs or on a pool between the
coping and the deck. This needs to be sealed with mastic. Sometimes builders use brown felt or green board instead of mastic. This option is less pleasing aesthetically. When this is replaced with mastic it not only improves the appearance of your backyard or outdoor area, but it also serves to seal out unwanted water underneath your concrete or pool coping / deck. Some older pool decks and concrete areas have white plastic strips between slabs of concrete. Replacing these with a mastic color to match your concrete can really improve and update the look of your outdoor area, and again, seal out water. Why is mastic important? Mastic is used in expansion joints, which are put in place to allow the earth to shift and move as it naturally does and to allow concrete to expand and contract. Mastic is a flexible material that moves with the earth and concrete while sealing out unwanted water. If mastic is not put in place or over time has pulled away from either edge and is not sealing out water, than you will begin to see problems with your concrete and/or pool. Concrete will begin to crack and lift as the water begins to saturate the soil beneath. If the mastic around your pool is old or deteriorated, water can saturate that joint and cause the tiles on your pool to fall off. Does mastic require maintenance? Mastic should be replaced when it is no longer sealing out water. On the average, mastic will last 3 years, but can last as long as 5 years (or as little as 1 year with extreme conditions).
