The word caulking might seem strange and confusing. But, it is an essential part of construction and home repair.
In this definitive guide on caulking, we will go over everything you need to know about caulk as well as some handy tips on how you can get started using the right tools to seal like a pro.
What is Caulking?
Caulking is the process of sealing small gaps between two planes or filling cracks to prevent moisture from entering inside.
If you have cracks or small openings in the exterior or interior walls, windows, floors, or ceiling of your home, then you may need to use caulk to fill in the open space. If left unchecked, this can allow moisture to seep into your home and can cause all sorts of problems including wood rot and bugs entering inside.
Caulk is a commonly used substance that offers years of protection when it is properly applied.
What is Caulk?
Caulk is a compound that is either based on silicone or acrylic latex that is used to fill gaps less than 1/8” at joints, cracks, depressions, and small openings.
When moist, the caulk is a paste that is applied normally from a tube to fill in the crack or opening. When the caulk cures, it dries and hardens to form a protective barrier that prevents moisture from entering or going through the wall.
What Is Caulk Made Of?
Caulk may seem like a wonder product, given its many different uses. But you may be surprised to learn that what makes up caulk is rather simple. In fact, there are two basic types of caulks, and each of them has its own attributes and subsets that make them special.
Caulk is mainly made from one of two types of materials, silicone and acrylic. You can also get polyurethane caulk and rubber-based caulk such as Flexshot.
Each material has its advantages and disadvantages. And they all have their specific uses, which makes them essential for sealing cracks and other home repairs.
Caulk made from silicone is inorganic and highly resistant to moisture. This makes it the perfect caulk to use in outdoor situations or when facing a considerable amount of moisture. It also is long-lasting and will hold up for several years, even under brutal conditions.
The downside is that silicone caulk tends to be more expensive, but the more important issue is that you cannot paint over silicone. It is because silicone is so non-porous that the paint simply peels off the surface. This means that it is not recommended to be used in situations where you want to paint over the surface.
Caulk made from acrylic tends to be less expensive and quite versatile. And unlike silicone caulk can be painted over once it has dried and been sanded. This makes it quite useful for many jobs around the home involving sealing cracks, gaps, and small openings.
The downside of acrylic latex is that it weakens quickly when exposed to ultraviolet light and the elements. Silicone is highly resistant to UV rays.
See the comparison between acrylic latex vs. silicone caulk for more details
Outdoor vs. Indoor sealant
As the name suggests, you should use outdoor sealant for areas that are exposed to sunlight and the elements. While indoor sealant should be used in areas not exposed to sunlight or the elements. That means silicone will mostly be used on the outside while acrylic is mostly used on the inside. However, there are exceptions.
Silicone is quite good in bathrooms, especially when sealing the bathtub from the interior wall. This area is noted for its moisture but also does not normally need to be painted. However, acrylic caulk that has been modified may be used in the bathroom and kitchen if you want to paint the surface.
Caulk comes in a wide variety of colors thanks to the dyes added to the caulk during the manufacturing process. It was not long ago that caulk only had certain colors and most of it was white. While white is still the most popular color or pigment for caulk, you can now find colors that may match the material in which you are using the caulk.
If you are using caulk with no intention to paint over it, then you should look for the color that best matches the surrounding materials. It may be possible to mix the same type and brand of caulk together to create new colors, but that would take extra effort.
What Is Caulk Used For?
The primary purpose of caulk is to create a moisture-proof seal. You will often find caulk used around window and door frames, where bathtubs connect to the wall, and any cracks or small openings in either exterior or interior walls, flooring, or the ceiling. But there are other uses as well.
7 Uses of Caulk Other Than Sealing Gaps
Caulk does have adhesive properties that allow it to stick to the surrounding material. It is part of the reason why caulk makes for the perfect sealant.
However, that adhesive quality also means that caulk can be used to stick trim molding, tile, or carpet back to the surface. Just dab a little on the underside and then stick the material back into place. While you can use other, stronger adhesives caulk works well in situations where the strength of the bond is not critical.
You will need to use outdoor, water-resistant caulk, but it can be used to fill cracks in the driveway before they become big issues. Look for a type of caulk with a similar color to the concrete or asphalt of your driveway. Otherwise, it will really stand out.
For surfaces that may be subject to fire, there is a special fireproofing caulk available to seal up holes, cracks, and gaps. Such caulk is quite good for interior framing, particularly around hot pipes or electrical wiring where a fire may begin.
4. Prevent Materials from Scratching Surfaces
If you have flowerpots or similar items that sit on the floor, they can scratch the surface. You can prevent that by turning the pots on their side and adding a few dabs of caulk to the bottom. Once the caulk dries, it will prevent the pots from sticking to the floor or scratching the surface if moved.
The dried caulk acts as a smooth buffer that works well for lighter items, but probably not heavy ones like your sofa.
5. Roof Repair
If you have a roof with small cracks, gaps, or openings, you can seal them up using caulk. Just wipe away any debris and loose particles inside the opening and run a line of caulk so that it fills up the gap. You can also use it as a sealant when you want to replace a damaged or missing shingle.
The only caveat is that you should perform such repairs when it is dry and not expected to rain until the caulk has dried for maximum effectiveness.
6. Smoothing Out Surfaces
Caulk can be used on some surfaces to fill cracks and other depressions. Once dry, the caulk can be sanded and smoothed out so it can be painted over. Normally, wood putty is used for wooden materials, but caulk is a good substitute if the material is going to be exposed to moisture or if the material is not suitable for wood putty.
One of the most annoying issues with placing wallpaper is that it tends to pull up when drying. However, if you run a line of caulk across the paper seams and especially along the corners, then smooth it out using a wet finger or sponge that will keep the wallpaper in place.
You can also use it on older wallpaper by lifting a section, applying a little caulk underneath, then sticking it back to the surface. Once applied, run a line of caulk along the seam to keep it from pulling up again.
Caulk comes in a tube, much like a toothpaste tube, with a plastic tip that is designed to be cut off at a 45-degree angle before use. The back of the tube consists of a solid plate that is designed to move forward and push the contents out the tip. So, unlike a toothpaste tube that you squeeze, caulk is pushed from the back to the front.
There are two types of caulking guns, manual and electric. Each has its benefits and issues, so you will need to consider all factors before making your purchase.
- Manual caulking gun: A manual caulking gun is a simple device where the tube is placed inside, a pusher plate is pressed to the back of the tube, and a trigger is used to push the contents out the tip. It is called a manual caulking gun because you do the work yourself without the aid of an electronic device.
Manual caulking guns are inexpensive and quite durable when used properly. The downside is that for long sessions of caulking, particularly if caulking is part of your daily job, can be quite taxing. The caulk takes effort to push out the tip even with the manual caulking gun.
- Electric caulking gun: A cordless device that operates on the same principle as the manual caulking gun, the electric version offers the advantage of being far less taxing to use. You simply press the trigger, and an electrical motor drives the piston forward. The advantage of a cordless caulk gun is that it pushes the caulk from the tube at a consistent speed producing a uniform bead..
There are different settings that allow you to adjust the amount of caulk that comes from the tip. You can produce a lot for bigger openings and smaller lines or beads to seal bathtubs from the wall. The downside is that, unlike a manual caulking gun that gives you a feel for how much is coming out, the electric one pushes out the same amount regardless.
How to Do Caulking?
Applying caulk with either a manual or electric caulking gun is basically the same.
- First, clean the application surface thoroughly to remove any soap, grease, and oil.
- Next, load the tube into the manual or electric caulking gun.
- Cut the tip of the tube at a 45-degree angle to create a small opening that allows the caulk to flow out.
- Set how much caulk will come out, line up the tip with one end of the crack or opening, then press the trigger and pull the tip across the crack until you reach the other end. The is known as applying a bead of caulk.
- If you are using a manual caulking gun, you will need to squeeze the trigger at the right pressure that allows the proper amount to flow out. It is generally better to apply too much caulk compared to too little, but you will have more to remove afterwards.
- Once the caulk is in place, allow it to dry. If you are going to be painting over the caulk, you will need to sand it after drying. This will not only flatten the caulk but help create a rougher surface so the paint will stick. Acrylic caulk can be painted over, but not silicone.
- Remove the sealant tube and clean the equipment.
- If you still have sealant left in the tube, wipe the tip clean and close the nozzle with a plastic wrapper to reuse later.
When doing repair works, remove the old sealing and thoroughly clean the surface for the caulk to adhere properly. Caulking over the old silicone is never a good idea.
Effects of Weather & UV Rays
Ultraviolet light or UV rays and the elements can affect even the strongest caulk. The continual exposure over time will break down even the strongest caulk. However, silicone caulk is far more resistant than acrylic caulk.
This is because silicone caulk is based on a non-organic source. Since UV rays break down organic materials, silicone is virtually impervious to ultraviolet light. Plus, its strong, rubber-like consistency makes it quite formidable against the elements as well. Rain, sleet, freezing temperatures, and hot conditions are highly resisted by silicone.
Acrylic is a different story, as it tends to break down over time when exposed to UV rays and the elements. Because it is made from more organic matter, it can dry out and fall apart when exposed to extreme conditions.
Exceptions include acrylic caulk that has been formulated to resist UV rays and strengthened to hold up against the elements. Plus, painting over the caulk will provide protection until the paint wears down.
How to Store or Save Caulk After Use?
You keep the caulk in the canister or tube and simply block the end so that air does not get inside. If you leave the end of the tube open, the caulk that is next to the opening may dry and block the rest from getting out.
Store the caulk in a cool, dry place on a shelf if possible so that it will stay in prime shape for years to come. If the caulk does dry out near the tip, you can cut the tip again and push out the dried material. Be sure to reseal it properly so that air does not reach the caulk. If a large amount of the caulk inside the tube has dried, then it is best to throw it away and purchase a new tube.
Back to Contents
- What is Caulking?
- What is Caulk?
- What Is Caulk Used For?
- Caulking Gun
- How to Do Caulking?
- How to Store or Save Caulk After Use?