Sealants

Caulking seals joints between building components. Most joints move because of changes in moisture and temperature in the building. Some materials can seal a larger joint and accommodate more joint movement than others. Choose carefully because there is wide variation among the same type of products produced under different brands. If possible, always select the premium product for long-term durability. Choosing the proper product and paying attention to the quality of application are crucial.

All sealants will require extra ventilation of the house after application to let the material cure. Typical curing time will be two or three days for interior applications. For application directions, see Caulking and other air sealing materials.

Materials labelled "for exterior use only" may not be suitable for indoor applications because they may contain volatiles that may be hazardous if inhaled in a confined space over an extended period. Read the manufacturer's literature carefully.

The following factors limit the effectiveness of caulking:

the flexibility and elasticity of the product. Some products can span a larger gap than others. Use a backer rod or foam rope in joints of 6 mm (1/4 in.) and larger before applying caulking to ensure an effective seal.
its compatibility with the materials being joined. Read the manufacturer's literature carefully.
its durability, paintability and curing time. If the product will be exposed to sunlight, make sure it is appropriate for this condition.
its ease of removal and reapplication. Some products can be used over previous applications while others cannot; some clean up easily with water, some require solvents, and some are very difficult to remove once cured.

Table 3-2 lists caulks and sealants available at most building supply stores. It is designed to help you select the best product for each application. If possible, always select a premium product for long-term durability.

Table 3-2 Air barrier caulking and sealants

Type	Bonds to	Application	Maximum joint	Comments
Acoustical sealant	metal, concrete, gypsum board and polyethylene	use only where sandwiched between two materials (not exposed to the exterior) staples required when sealing joints in polyethylene can be reapplied over itself	16 mm (5/8in.) accepts 10% joint movement	good durability: 20 years non-hardening not paintable
Butyl rubber caulk (synthetic rubber sealant)	most surfaces but particularly suited to metal and masonry	generally used on exterior ventilation required during application and curing (up to three days) difficult to smooth	13 mm (1/2in.) accepts 5 to 10% joint movement	low to moderate durability: 5 to 10 years available in a variety of colours paintable after curing
Silicone sealant caulk	most non-porous surfaces primers may be required on wood, steel or anodized aluminum cannot be used over existing silicone	interior and exterior grades ventilation required during application easy to smooth flexible, watertight seal when cured	25 mm (1 in.) with backer rod accepts 12 to 50% joint movement excellent for large moving joints	good durability: 20+ years available with fungicide for wet locations and in a high-temperature type for use around chimneys/vents available in colours and clear most types not paintable paintable types less durable
Polysulphide caulk(synthetic rubber sealant)	stone, masonry and concrete surfaces when used with a special primer may attack some plastics	generally used on exterior can be used below grade ventilation required while curing moderately easy to smooth flexible upon curing	25 mm (1 in.) with backer rod accepts 12 to 25% joint movement	very good durability: 25+ years available in several colours paintable
Polyurethane caulk (urethane)	most surfaces preferred choice of window and door installers	exterior use only ventilation required while curing long curing time can be hard to smooth flexible upon curing can be reapplied over itself	25 mm (1 in.) with backer rod very stretchable: up to 50% joint movement	very good durability: 25+ years limited colours paintable
Acrylic latex caulk	most surfaces	interior and exterior use ventilation required when curing easy to smooth	10 mm (3/8 in.) accepts 7 to 10% joint movement	low to moderate durability (varies by brand): 5 to 25 years water cleanup comes in colours paintable
Acrylic latex with silicone caulk	most surfaces	interior and exterior use ventilation required when curing easy to smooth can be reapplied over itself	13 mm (1/2 in.) accepts 10 to 15% joint movement	very good durability: 30+ years water cleanup paintable
Elastomeric latex sealant	most surfaces	interior (some brands only) and exterior use ventilation required when curing flexible upon curing moderately easy to smooth can be reapplied over itself	25 mm (1 in.) with backer rod accepts 50% joint movement	very good durability: 30+ years water cleanup limited colours paintable
Urethane foam sealant (low, medium and high expansion types)	most surfaces except Teflon, polyethylene or silicone plastics	interior and exterior use use only low expansion type around window and doorframes or risk bowing can be used below grade ventilation required during installation can be reapplied over previous foam protect from sunlight	check the can for expansion rates and sizes of cracks that can be filled very good for filling larger joints and cavities like header/joist intersections, around indoor and outdoor plumbing and vent openings, and wiring holes	good durability: 10 to 20 years available in individual aerosol spray cans and dispensing systems with spray nozzles hard consistency when cured use gloves and a drop cloth: impossible to remove residue after curing use acetone to clean up uncured foam paintable
Latex foam sealant	most surfaces	interior and exterior use must be covered for exterior use due to open-cell structure not for use below grade ventilation required during installation extremely flammable during application: read precautions on the product label can be applied in successive layers difficult to smooth	will not over expand - reaches 75% of size upon application recommended around window and door frames, but requires a vapour barrier	good durability: 10 to 20 years cleans up with water soft, spongy consistency when cured paintable
High-temperature stove or muffler cements and non-combustible sealants	most materials typically used in conjunction with other materials for sealing around masonry or factory-built chimneys	interior and exterior use for use in high temperature applications easy to smooth	no joint movement	very good durability compatible with high-temperature silicone sealant check product for CSA or UL rating for high-temperature use available at heating equipment supply stores

TECHNICAL NOTE:

Be mindful when using caulks and sealants. Urethane foams are impossible to remove once cured, other products are flammable. Read manufacturers' literature and take proper precautions during installations (wear gloves, etc.).

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