Sealant Buying Guide

Polyurethane sealant, a type of mastic sealant, is a great all-purpose option for sealing and bonding two different materials, including metal, glass, tile and wood. Mastic sealants do not need a primer and there are a range of options available for different jobs, including anti-mould, window and door, or multi-purpose. They're often used for tasks like sealing tiles, windows and doors, or filling cracks in walls or ceilings.

Polyurethane sealants are very flexible and suitable for a range of materials. This type of sealant can be adjusted for hardness and strength depending on the project they’re designed for – including being able to resist UV damage and corrosion over time to compete with silicone alternatives. 

Because polyurethane mastic sealants are organic, they begin to return to their original polymer form over time unless hardened for specific applications such as use outside. As a result, some general purpose polyurethane sealants will not be suitable for outdoor use or in extreme conditions. However, as this sealant type is easily hardened, there are many options for different applications.

Silicone sealant is a type of adhesive gel substance that is commonly used in bathrooms to create a watertight seal, but is also a common choice elsewhere in the home and in industrial settings. They cure over time by simply drying until a rubbery consistency is achieved. Silicone sealants come in a variety of colours, but are most commonly white, grey or clear. 

You’ll find many silicone sealants with anti-mould and mildew qualities making them ideal for wet environments. A range of options are available depending on your project, whether you’re working indoors or outdoors. Unlike polyurethane, silicone sealants are not organic, so they won’t degrade back to their original form over time once cured.

Make sure to consider the qualities of specific silicone sealants compared to the job you’re taking on – such as UV resistance, quick-drying, non-flammable, or non-corrosive features. Silicone is fairly hard wearing in both warm and cold climates once cured, but extreme conditions – especially when being applied – can still affect the performance of silicone sealant. Also, silicone sealant cannot be painted over compared to acrylic alternatives.

Decorators caulk, also known as acrylic sealant, is made from water-based acrylic resin. It is used around the home to fill cracks and gaps, such as around skirting boards, and provides a moisture-resistant seal. Decorators caulk is also used in joinery and construction settings as it can be applied to a range of materials including metal, PVC and wood. 

One of the main advantages of decorators caulk is that it can be painted over, making it perfect for filling cracks in walls prior to painting. Acrylic sealant is also resistant to moisture as well as low and high temperatures, so it is fairly versatile for a number of applications.

While moisture resistant, decorators caulk is not suitable for situations where it will be subject to direct water exposure, including around a bath or shower. For this reason, most jobs that need a moisture resistant seal are better suited to silicone sealant – unless it needs to be painted over. You’ll also find that decorators caulk is not as easy to work with than silicone sealant and may need more skill to achieve a professional finish.