Caulk or caulking is a flexible sealing material used to seal air or moisture leaks through joints, cracks or gaps that are less than a quarter inch in thickness. It is used between stationary building components and materials. When it comes to moving components such as windows and doors weather-stripping is the appropriate material to use.
Before caulking air leaks it is important to detect any leaks that require caulking and asses the ventilation needs of the room you are working in to ensure proper indoor air quality. As well as sealing air leaks caulking is also applied indoors and outdoors the prevent moisture and water damage like around faucets, water pipes, drains, bathtubs and other plumbing fixtures.
Caulking compounds is usually sold in disposable tubes that fit into a “half-barrel” caulking gun. Some types of caulk come in squeezable tubes that do not require a caulking gun for application, aerosol cans and ropes for smaller projects. When purchasing caulking compound remember that on average you will need about half a tube for one window or door and about four tubes of caulking compound for an average homes foundation sill.
Caulking compounds have different properties which vary in strength and durability. Water-based caulk is easily cleaned with water whereas solvent based caulking compound will require a solvent for proper cleanup.
The following are some choices of caulking compound, their recommended uses, and their properties.
Silicone (household)-Used to seal joints between bathroom and kitchen plumbing fixtures as well as tiles. Household silicone Can be cleaned with water or a dry cloth if still wet. Some scraping may be required if dry. Household siliconDoesn’t shrink very much. Excellent adhesion properties. Flexible when dry allowing joints compress and expand.
Silicone (construction)- Seals most construction materials like wood, stone, metal, concrete and brick. Construction silicone can be cleaned with a solvent such as a thinner. Construction silicone does not shrink but expands. Silicone has excellent adhesion qualities. Permits joint to expand and compress.
Polyurethane (expandable spray-foam)- Indoor or outdoor use. Good for larger cracks. Should be used in stationary non-friction areas as spray-foam will become dry and powdery over time. Wash with solvent when wet, scape off when dry. Polyurethane spray foam doesn’t shrink but expands quite a bit. Polyurethane foam has excellent adhesion properties. Spray foam type caulking expands quickly to fill large irregular shaped gaps. Polyurethane is flexible and can be applied at variable temperatures. Expandable spray foam must be painted when used outside to protect from the sun.
Water-based foam sealant- Applied to windows and doors and also used to fill small cracks. Foam sealant can be cleaned with water. Does not shrink, expands approx. 25%. Excellent adhesion.Water-based foam sealant takes 24 hours to fully dry. Water-based foam sealant is not useful for large gaps or spaces as drying becomes difficult. Water-based foam sealant be exposed to air in order to dry.
Butyl rubber- Seals most dissimilar construction materials like glass, metal, plastic, wood, and concrete. Used around windows and doors, flashing or to bond loose roof shingles. Butyl rubber is cleaned with
mineral spirits or naphtha. Butyl rubber shrinks a little from 5 to 30 percent. Butyl rubber has good adhesive properties but does not adhere well to painted surfaces. Durable, resilient and non-brittle butyl rubber can last ten years or more.
Latex- Latex is used to seal joints around showers and bathtubs. Latex can also be used to fill cracks in tiles, plaster, glass, plastic and to fill nail holes. Latex can be cleaned using water when wet and scrapes off easily when dry. Latex shrinks very little on 5% to 10%. Latex caulking has very well to all surfaces except metals. Latex caulking is easy to use. Seams can either be trimmed or smoothed out with a wet finger. Latex can be sanded and painted and is water resistant when dry. Latex caulking has varied durability (from 2 to 10 years). Latex caulking has little flexibility once dry and must be painted if used on an exterior surface.
Oil or resin based caulking- Used to seal exterior joints and seams on most building materials. Cleaned with mineral spirits or naphtha. Oil or resin based caulking shrinks 10% to 20% when dried. Oil or resin based caulking has good adhesion qualities except on porous materials where adhesion is poor. Oil or resin based caulking comes in squeezable tubes and ropes. Oil and resin based caulking compound has low durability (1-4 years) and should be painted after application.