Many projects require some kind of adhesive or sealant, and it is important to use one most appropriate for any particular task. Many types are available, some can even act as both an adhesive and sealant. Here’s a guide to common adhesives and sealants.
As there are many different materials that you are working with, adhesives are often designed specifically for the task at hand. Varieties include ‘nail gap filling’, ‘tile adhesive’ or ‘roof felt adhesive’, for instance. Some materials will only work with certain adhesives, such as UPVC. You may find some adhesives react differently with certain materials, such as mirrors that can be stained by all-purpose adhesives.
Adhesives, or glues, also come in a variety of applications, such as hot glue, or spray adhesives. Again, consider what the job is you’re carrying out and what may offer you the best result.
PVA, or Polyvinyl acetate adhesive, is a thick white liquid that can be used in many different forms. It often comes in a concentrated form and can be used as an all-purpose adhesive. It may be used neat, as a glue, or diluted, as a surface sealer, bonding agent or primer. Waterproof PVA is also available.
Contact adhesives are perhaps the most common forms of adhesives because they can be used to bond a large range of materials including wood, metal, many plastics, and decorative laminates. It is not suitable for use with some materials, such as polystyrene and bitumen, or as a mirror adhesive, so check the instructions before using it.
Super glue is a type of contact adhesive, when used in DIY / construction it should be industrial strength.
Wood glue is similar in appearance to PVA but is designed specifically for bonding sections of wood. It is often resin based and has a fast cure so that it’ll set quickly, yet still provides high strength.
Grab adhesives are used to bond surfaces that cannot easily be fixed with screws or nails. Can be used both inside and outside and adheres to just about every building substrate. Available in tubes and sealant-like cartridges.
Some sealants prime or seal a surface while others create a decorative, waterproof or durable point. Most joint sealants have a waterproofing element, often with silicone as the main ingredient.
Joint sealants usually come in cartridges that require a separate dispenser to apply them. They also often are available in a range of colours, and some can be painted (but not silicone varieties).
The most important element of sealant is that it must cope with movement, such as that caused by temperature changes, in the materials they join. “High-modulus” sealants are not very flexible, but dry to a relatively hard finish, and are recommended for use in bathrooms. “Low-modulus” types are more flexible and are used in glazing.
Most sealants form a skin quickly, but take several hours, even days to dry or cure completely. A sealant should never go completely hard, because of the need for flexibility.
Bath and shower sealants are designed to provide the best waterproof seal. Check that it has an anti-fungal compound added.
Bitumen paint is a sealant that can be painted on. It provides an anti-corrosive, anti-rust and waterproof solution on a wide range of materials, but especially on iron and steel.
Building sealants are designed specifically for certain tasks / areas in a building. Such as fire-retardant sealant where heat and fire resistance is required, or roof and gutter sealant where a waterproof, flexible solution is needed to bond guttering. Gasket sealants are also available for sealing and bonding gasket joints where high temperature resistance is needed, such as industrial ovens or engine parts.
Expanding foam is supplied as an aerosol and is used to fill large cavities, bonding to their edges. Polyurethane-based expanding foam is often used in general construction and DIY. Some varieties have greater heat resistance than others. This is an important feature in some situations such as when fitting a flue.
Frame sealants are designed for Internal and external sealing around timber and metal window and door frames.
There are also some general-purpose sealants, often used for plumbing, decorating or glazing purposes. It is essential to check you’re using the correct sealant for the task, so you achieve the desired result and longevity.