Whatever the reason, almost every home owner has at one time or another purchased a tube of caulk. Over the last few years, much has changed in the world of caulk. If you doubt it, just walk into any hardware store and check out the caulk department. Today, we can easily be overwhelmed by the number of compositions, colors, and containers.
So how does one decide which caulk is the most appropriate one to purchase? The first consideration in selecting the right caulking compound is to consider the application. Is it for interior or exterior use? What are you trying to achieve - is it to weatherproof, hide unsightly gaps or blocking drafts? And does the application need some flexibility?
There are many formulations on the market, many of which combine basic ingredients in different ways to enhance such characteristics as cure times, ease of cleanup, longevity and flexibility.
Chemically speaking, there are five common types of caulk.
Latex: Latex caulks are easy to work with. They are basically water-based caulks that are applied as a liquid. They have the least ability to stretch and thus they work best on interior applications where little movement is expected. Nowadays latex is often combined with another type of caulk, like acrylic, to enhance their performance. The life span of latex caulk is 5-10 years.
Acrylic: These caulks consist of a family of synthetic resins that are water-soluble and clear. They can be painted and cleaned up with water thus making them good for touch-ups and for filling small gaps. A high performance acrylic caulk, called elastomeric caulk, is designed for greater elasticity and is the favorite for those that value speed and ease of application. The life span of acrylic caulk is 5-10 years.
Butyl: This is one of the oldest and most affordable types of caulk. It has good adhesion and weather resistance so it is popular for sealing gutters, chimney flashings, walks and exterior joints. It is solvent based and characteristically stringy which makes it difficult to apply in a finished quality joint.
Polyurethane: This type of caulk is preferred for outdoor applications where high-quality in important. This caulk bonds to most surfaces including masonry and metal, holds up well to heavy movement, has tremendous bonding ability, and can be painted. Because of its bonding ability, removal usually involves cutting or sanding unwanted caulk. Also, a paint thinner is needed for cleanup as it is a solvent-based material.
This is a popular caulk for filling indoor gaps in floorboards because polyurethane can take the high-traffic stresses of floors. However, for most indoor applications, the use of a polyurethane caulk is "over-kill". Polyurethane caulk is a harder caulk to control and takes longer to set up. Because it is more difficult to work with, acrylic latex caulk is often perfectly suitable. Polyurethane has a life span of 10-20 years.
Silicone: This product incorporates 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 caulk is basically non-porous so it is excellent for making something watertight. Therefore, it is most often used in shower and sink applications and glasswork. It is rubbery but does not stick as well as other caulking compounds. Up until recently they could not be painted. However, new hybrid siliconized acrylics are available that offer greater elasticity and are paint-friendly.
General Information: The primary goal of interior caulking is to seal against drafts along exterior walls and at intersections and prevent water intrusion at plumbing fixtures. A thin bead of caulk can also hide unsightly gaps and make joints easier to keep clean. Exterior caulk is good for shedding water and making your home more weather and draft resistant.
One secret to an attractive and long lasting caulk job is good preparation and meticulousness. Surfaces should be very clean before caulking. To help produce a attractive application, mask off the surrounding area with tape. Always have cleaning materials ready and remember that for solvent based caulks like polyurethane, paint thinner can leave stains on nearby finished surfaces. Never depend on caulk alone to fill a gap wider than ¼". For gaps bigger than this, first insert some foam cording in the gap and then fill with caulk. How well caulk fills the gap also depends on environmental exposure, such as shifts in temperature, ultraviolet light, weather and building movement. Always carefully read the product label for application purposes and check out the manufacturer's website.
Peter Ottowitz, New World Home Inspections and Energy Audits
Certified Master Inspector
Certified Environmental Home Inspector
Certified Residential Mold Inspector
Licensed Construction Supervisor
