Why use caulk? What is its purpose?
Caulk is made to seal out water, air, dust, pollution, insects and noise. Caulk can also simply dress up or give a finished look an otherwise rough-appearing joint.
Most normal latex caulks will crack and fail over time. They are unable to hold their seal. Higher quality products, referred to as sealants, will hold their seal over many years.
They are able to withstand the normal movement that occurs with weather changes.
The following tips will give you the basics of how to caulk to get the most value out of the product, as well as your time and effort. By following the guidelines below you will reduce the risk of failure
and increase the chances of achieving a sound, durable and attractive seal for many years to come.
1. Watch the Weather
Weather Affects Performance
Pay attention to the weather, as it can affect:
- the size of the joint at the time of caulking
- the contaminants on the surfaces of the joint (like dust, pollen, etc.)
- the ability of the caulk to "wet" the surfaces of the joint for good adhesion
- the ability of the caulk to properly cure and develop its ideal physical properties
Ideal Weather Conditions
Plan to caulk in ideal temperatures whenever possible. What is ideal? 50°F and rising and 90°F and falling.
Be sure to pay attention to the surface temperature where you'll be applying the caulk. It should also fall within that idea temperature range.
Wet / Snowy Conditions
If it has just rained or snowed, allow the surfaces to completely dry before caulking. Wet surfaces will make proper adhesion difficult and may inhibit proper curing of the caulk.
In the same way, avoid applying caulk - even in ideal weather – if rain or snow is expected within 24 hours. If you need to get the caulking done, go ahead and do it.
Just make sure to cover your work with a plastic tarp to prevent moisture from getting onto the caulk and causing it to wash out.
It is never good practice to apply caulk in extreme temperatures. Whether hot or cold, the joint will not be at its ideal size, the caulk will not cure correctly (which causes performance problems),
or the caulk may develop blisters. Any weather-related problems with the caulk can be fixed fairly easily, but are also avoided altogether through simple weather watching.
2. Prepare the Surfaces and the Joint for Sealing
Good surface and joint preparation is the #1 requirement for a professional and long-lasting caulking job, whether you're replacing old caulk or sealing a new joint for the first time.
Here's how to go about cleaning:
- Use a putty knife, painter's 5-in-1 tool or other similar tool to remove all of the old caulk in the joint. A heat gun can be used to soften old caulk and loose paint to make removal easier, or caulk remover can also help remove all types of old caulk.
- Make sure the surface is completely free from old caulk, peeling paint, weathered wood fibers, grease, oil, wax, pollen, dirt, rust, mold, mildew, soap scum, etc. A wire brush works well to remove contaminants, and a drill-mounted wire wheel is often the best answer for cleaning dirty, unsound concrete. To clean off oil or grease, use a grease-cutting cleaner and thoroughly rinse. Remember, the best caulk in the world won't work if it is applied to a dirty or unsound surface.
- Finally, ensure the surface is rinsed clean if you used a chemical remover. Chemicals can also interfere with proper adhesion.
Use Backer Rod
If the joint or crack will be 1/4" wide or wider, it is best to install foam backer rod (like foam rope) in the joint before applying the caulk. Why use backer rod?
- It saves money. Backer rod is cheaper than a quality caulk. By filling the joint with the backer rod, you avoid filling the joint with the more expensive caulk.
- It helps provide the ideal joint design (two points of adhesion with less product applied in the middle of the joint), which aids in both performance and easy fixes when there is extreme movement and the caulk can't hold its seal. For more info on proper joint design, see the product brochures.
- Tooling is improved. More pressure can be applied to the caulk when a backer rod is behind it. This added pressure forces the caulk into intimate contact with the sides of the joint for better adhesion
How to Install Backer Rod
Simply press the material into the joint using your hands or an appropriately sized tool. It should be shoved deeply enough to allow for 1/4" – 1/2" depth of the caulk applied over top.
If you are using closed-cell backer rod, avoid putting holes or nicks in it because the damage can lead to "out-gassing" from the backer rod and may cause blisters in the sealant.
Then, masking tape can be applied to both sides of the joint before caulking to prevent smearing and create a clean caulk line.
If the joint or crack will be subjected to regular difficult stress, such as continual water submersion at the bottom of a swimming pool or a home in extreme wind, it is important to use a primer before caulking.
For a home, normal paint primer will do the trick. In swimming pool or other unique situation, contact us for recommendations.
The caulk will adhere better to primer, giving it better long-term performance and will require less maintenance over time.
3. Use the "Best" Sealant for the Job
A water-based acrylic latex like Big Stretch® may be perfect for one area, where in another you'll need a co-polymer rubber like Lexel®.
Check out the Usage information for Sashco products to help determine which product will be best for your job.
4. Apply the Sealant Properly
Cutting The Nozzle
Embossed markings are included on each cartridge nozzle and correspond to different bead sizes. Cut the nozzle at the mark for the bead size you'll need for your job. It's easy!
Simply cut the nozzle at a 45° angle, puncture the inner seal (if there is one), place it in a caulking gun, and you're ready to begin. (Obviously, no caulking gun is required with a squeeze tube.)
Before you actually start to caulk, do some practice caulking on a newspaper or paper towel to get a better idea for how the product feels. Practice pulling it in a consistent manner to avoid getting weird breaks
when you have to pull the trigger again. It is best to pull the nozzle along the joint, rather than pushing it. Pulling it allows the nozzle to smoothly slide over any bumps on the surface; pushing usually leads to
more hang-ups and sudden stops.
Applying A Bead of Caulk
When you're comfortable, start your first caulk line in an inconspicuous area. Hold the caulking gun or tube at a 45° angle parallel to the joint. Only apply 2-3 feet of caulk at a time so you have plenty of time
to tool it before it starts to dry and skin over. By the time you get to those areas that are more noticeable, your new-found skill will shine through with beautiful results. If you do mess up, simply scrape out
the bead right away and start over.
The Art of Tooling
"Tooling" is the process of gliding over the bead of caulk in order to smooth it, making it neater and further establishing good adhesion. Is tooling necessary?
Absolutely! Caulk is made to not flow, so tooling is critical for proper adhesion and sealing. Tooling can be done with a finger (covered with a latex glove, wetted with some water or solvent, or just bare -
depending on the caulk used), or with various tools, like the back of a spoon, a trowel, or Sashco's favorite foam paint brushes. Try not to scrape off too much of the caulk during tooling.
This may starve the joint of caulk, as well as waste a lot of it. Keep rags handy to clean up any mishaps, and clean up any problem areas right away. Dried caulk is hard to remove! If masking tape is used
along the sides of the joint, make sure the tape is removed immediately after tooling is complete (before the caulk skins over) so that it will pull away cleanly and leave a smooth, even line.
It's been reported that most houses have leaks equivalent to leaving a 2-square foot window open all winter long. Seal those leaks, save on your energy bills and spend that money on something better.
Where to Start
Check all of your existing windows and doors. All you need is a caulking gun and a few cartridges of high-quality caulk and you can make your home cooler in the summer,
warmer in the winter and more resistant to moisture and bugs all year long.
Some Helpful Tips
- Your furnace can create a slight amount of air pressure inside your house when it is running. As you seal the cracks in your house with caulk, you might have small bubbles develop in the caulk while it's still wet due to this pressure pushing on the caulk bead. To minimize this risk, leave one or more of your windows slightly open just for a couple of days while the caulk firms up so that it can resist this slight pressure.
- It's a good idea to fill the large voids between the window frames and the framing of the stud walls (covered by the window trim boards). But don't use highly expanding foams that can actually expand too much and put too much pressure on the window, causing them bow inward. This can obstruct the movement of the windows themselves.
- If your caulking project coincides with painting or staining, make sure the paint or stain you use will work with the caulk you're using. If the paint or stain contains wax, stearates, silicones, paraffinic oils or similar ingredients, the caulk will not adhere very well. Contact us with your questions. You'll save yourself a lot of time, money and effort using products that work together.
- As long as the products work well together, it is usually best to do all your painting or staining first—including the joints to be caulked—before caulking them. The paint or stain acts as a primer for the caulk, improving the overall adhesion and performance.
- Make sure you don't skimp on caulk. The bead should be at least 3/16", or bigger when possible. This ensures there is enough mass of the caulk to easily handle the inevitable movement that occurs with humidity and temperature changes.