What is mastic?
In UK construction and trade language, 'mastic' is often used broadly to describe joint sealants and the act of sealing. It can refer to several types of product including silicone, polyurethane, polysulphide and acrylic sealants. When someone asks for a 'mastic man', they usually mean a sealant applicator.
What is silicone?
Silicone is one type of sealant chemistry. It has excellent flexibility and water resistance, which makes it popular for bathrooms, kitchens and some external weather-sealing applications. Specialist silicones are also made specifically for glazing, façades and other external uses.
Which sealant is right for the job?
The right product depends on the substrate, joint size, expected movement, exposure, compatibility with adjacent materials, and the manufacturer’s technical guidance. Silicone is often suitable for wet areas and some external glazing, while polyurethane, polysulphide, hybrid or acrylic systems may be better for structural, high-movement or façade joints. We select the right sealant for each application rather than using one product everywhere.
Frequently Asked Questions
Can you use silicone outside?
Some silicones are formulated specifically for external glazing and façade weather-sealing. The suitability depends on the particular product and its intended use, not the chemistry alone.