Submitted by: Dwayne Boggs (Dwayne is a home inspector serving the Thurston County area home inspection market)
A major part of home maintenance is caulking and painting your home. So before you paint you will need to caulk all exterior gaps to help seal the home from moisture. So I will explain the types of caulking and where to use them.
Caulking is not a new concept. For centuries, natural materials, such as pitch and bitumen, have been used to fill gaps in all kinds of structures. However, what really separates today’s building caulks, or joint sealants, from earlier materials is the use of synthetic polymers, first developed in the 1930s. Polymers are substances formed by inducing small molecules of one kind to link up and make large molecules of a similar nature; they are the chemistry behind the rubber-like characteristics of modern caulks. Though the dozens of different tubes on a lumberyard shelf may present a daunting selection, the residential caulk market can be boiled down to five common caulk chemistry types.
Butyl. Based on a man-made rubber, butyl is one of the oldest and most affordable caulk types. Butyl caulk is solvent-based and characteristically stringy, which makes it difficult to apply in a finish-quality joint, but its admirable adhesion and weather resistance continue to make it popular for sealing gutters, chimney flashings, walks, and other exterior joints.
Latex. A general term for a rubber-based caulk that is applied as a liquid, latex caulks are usually water-based. Because basic latex caulks have the least ability to stretch (rated around 7% to 10% elasticity), they work best in interior applications where little movement is expected. These days, latex is often combined with another caulk type, such as acrylic, to enhance performance.
Acrylic. In caulks, acrylics are a family of synthetic resins that are clear as well as water-soluble. Like latex caulks, acrylic caulks are easy to work with because they can be painted and cleaned up with water, making them good for touch-ups and for filling small gaps. Elastomeric caulk, a generic term for high-performance acrylic caulk, is designed for greater elasticity and is quickly becoming a favorite in a market that values ease and speed.
Generally, acrylic and latex caulks have a life span of five to 10 years, depending on environmental exposure, such as temperature shifts, ultraviolet light, weather, and building movement. These caulks can usually be removed by simply pulling them up or by using a utility knife to cut them away. Acrylic latex hybrids might include more solids, such as butyl, to offer greater product strength and integrity.
Silicone. Silicone caulk is formulated from silicone elastomers, or in simple terms, linear polymers of silicone oils that can be coaxed to cross-link in a couple of ways. For residential use, this means incorporating chemicals that induce the polymers to room temperature vulcanize or RTV. (This process releases acetic acid as a by-product, producing a vinegar scent.) Silicone is virtually non-porous so its big advantage is to make something watertight, and it’s most often used in plumbing applications (shower and sink installations) and some glasswork. Silicone is extremely rubbery (50% elasticity) but does not stick as well as other caulking and in its pure form, can’t be painted. There are now some hybrid siliconized acrylics that offer greater elasticity and a paint-friendly surface; they may be worth a try in an indoor setting where flexibility is critical.
Polyurethane. Polyurethane caulk, which is based on the reaction of a glycol with an isocyanate to form a compound, is preferred for outdoor applications, with high-quality products having an exterior life span of 10 to 20 years, depending on exposure. Polyurethane products bond to most surfaces, including masonry and metal, hold up to heavy movement (25% elasticity), and can be painted. These traits also make these products great for filling indoor gaps in floorboards because polyurethane can take the high-traffic stresses of floors.
The polyurethane products are overkill for other indoor application, because the material is much harder to control and takes longer to set up where acrylic latex would be perfectly suitable. Polyurethane caulks have tremendous bonding ability-so much so, that they can also be used as adhesives in some circumstances-but this tenacity does make them more challenging to work with.
Polyurethane is solvent-based, meaning that you must use paint thinner for cleanup. Early polyurethanes had to be mixed from two parts in the field like epoxy, but the new products come in one-part formula tubes ready to use. Due to their adhesive strength, removal usually involves cutting out or sanding off unwanted caulk.
Always read the product label carefully for application purposes, and take advantage of product websites and contact numbers before making a sticky mistake. Like most purchases, you get what you pay for, so the cheaper the caulking is, the less- solid components it will contain, resulting in a poorer performance and more shrinkage. Because we’re talking about a jump from $2.00 to $7.00 a tube here, the investment is well worth it.
About the Author
Dwayne is a member of the Olympia Master Builders and a former past President of the Washington Association of Property Inspectors, Dwayne is also a committee member for the Washington State Pest Management Association (WSPMA), Dwayne has been serving the Thurston County home inspection markets of Olympia home inspection , Lacey home inspection and Tumwater home inspection for many years. Boggs Inspection Services can be reached at 360-480-9602.
