Knowing how to caulk windows includes learning how to choose the right tools, prep the area, and apply and smooth the caulk. I’ll share firsthand tips and explain the process step-by-step.
I live in Pennsylvania, where temperatures fluctuate between -10 and over 100 degrees Fahrenheit. We understand the significance of staying comfortable indoors while lowering our electric bills. By properly sealing our windows with caulk, we can prevent the frigid winter winds and the sweltering summer humidity from getting inside.
Caulking is only one way to make your windows more energy efficient. For more tips, check out our comprehensive guide: How to Weatherproof Windows.
| Project difficulty: Beginner Estimated time to complete: 2-3 hours (with additional 12-15 hours of drying time.) Project cost: Caulk prices start at $5 per tube. You may need to purchase tools or supplies if you don’t have them already. |
Job Parameters
If you’re just starting out as a DIYer, caulking windows is an excellent way to dive into home improvement. It’s easy enough for beginners, won’t break the bank, and you can complete it fairly quickly from start to finish.
The time required to caulk a window varies based on several factors, such as the size and condition of the window, the weather conditions (humidity and temperature), and the type of caulk used.
Project difficulty: Beginner
Estimated time to complete 8-10 windows: 2-3 hours
Drying time: 12-15 hours
Project cost: Caulk prices start at $5 per tube. You may need to purchase tools or supplies if you don’t have them already.
Tools and Supplies
- Long-nosed pliers
- Putty knife
- Large paintbrush
- Retractable razor blade
- Long nail (if you don’t have a caulk gun)
- Caulk gun
- Cartridge caulk
- Rubbing alcohol or a bucket with soapy water
- Cotton rags
- Blue painter’s tape
- Bucket/trash can for the waste
Caulk Guns
A good caulk gun makes your job easier. In today’s market, the smooth rod (dripless) caulk gun and the ratchet caulk gun are common. I recommend getting the smooth rod, also known as a dripless caulk gun, because it allows for better control over how the caulk flows.
My Tip: As a kid, my dad caulked the windows around our home. If my dad had been able to use a dripless caulk gun, instead of the ratchet, he would have had a lot less mess and more control when applying the bead. Unfortunately, the dripless model didn’t exist back then.
Caulk
When choosing caulk, it’s important to consider which type is most suitable for the window material, whether you need interior or exterior caulking, and if you plan to paint it after it dries. And if you’re using a caulk gun, buy caulk that’s in a cartridge.
If you’re not ready to commit to permanent caulk, you might want to try semi-permanent rope caulk. It provides a quick, easy, and temporary solution for addressing drafty gaps in your windows.
Note: You might have heard the terms “caulk” and “sealant” used interchangeably. While they are both used to stop leaks and fill gaps, they differ in durability, usage, and flexibility.
Best Temperature to Apply Window Caulk
Caulk performs best in low humidity, with temperatures ranging from 40 to 90 F. Within this temperature range, the caulk adheres well and is flexible to work with, creating a strong seal that dries effectively.
My Tip: In Pennsylvania, we plan our window caulking projects when the weather is dry (no rain), humidity is low, and in late spring to early fall when temperatures are within the ideal range. It’s also a good idea to consult the label for the manufacturer’s recommended temperature range and drying time.
Prepare Your Windows for Caulking
Before you start caulking your windows, it’s important to consider which parts should be caulked and which should not. Then, remove old caulk and debris, clean the area, and you’re ready to caulk.
Where to Caulk (and Where not to Caulk)
Interior of the window: When caulking the interior of your windows, your goal is to seal out the drafts and make it look nice. So, the parts of the window you’ll address are where the window trim meets the wall, any stationary (fixed) parts, and window sills.
Avoid caulking any weep holes, moving parts, and sliding tracks (single-hung and double-hung windows). Additionally, you might want to paint over the new caulk to match the rest of the room when the caulk has cured.
Exterior of the window: The primary aim of caulking exterior windows is to seal gaps to block water, drafts, and energy loss while allowing proper drainage (weep holes) and ventilation.
On the exterior, concentrate on the gap between the window frame and the siding or wall, between trim pieces like corners and joints, and non-moving (fixed) parts. Avoid weep holes, moving parts, and sliding tracks.
Remove the Old Window Caulk
When caulk starts to deteriorate, it loses its ability to create a good seal, allowing water, bugs, and air to get in. These problems can lead to water damage, mold, mildew, and rotting wood. To prevent this, it’s essential to prepare the surface properly.
Use a putty knife and/or utility knife to cut and pull off the dried caulk; long-nose pliers can also help you easily grab and take it off.
Inspect and Remove Any Debris
Once you’ve removed the old caulk, take a moment to examine the area for any leftover bits of hardened caulk or dried paint and carefully eliminate them. You can use an old rag or a large paintbrush to clean away any remaining debris and dirt.
If your house has a brick or stucco exterior, these surfaces tend to have a rough texture that can trap dirt more easily. (You can see this in the video further down.) So, ensure you’ve taken a bit of extra time to remove as much dirt as possible from these surfaces before the next step.
Clean the Area
At this stage, you want to achieve a clean surface before applying the caulk, ensuring that the new caulk adheres effectively and forms a durable, waterproof seal.
There are two ways to clean the area: Some homeowners opt for warm, soapy water, while others choose rubbing alcohol.
The goal is to remove dirt, mold, mildew, tree sap, and other buildup. After selecting your cleaning method — either warm, soapy water, or rubbing alcohol — you should clean the window thoroughly and allow it to dry completely.
Apply Caulk to the Windows
Prepare Your Caulk Gun and Caulk Tube
You can cut your cartridge tube in two ways: with the caulk gun or a utility knife. If your caulk gun has a hole in the handle, that’s called the spout cutter, and you can use that to cut your caulk tube. If not, use a utility knife.
My colleague Sarah shared this tip: The size of the gap determines the size of the cut. If you have a small gap, make a shallow cut so the bead of caulk will be small. For larger gaps, make a deeper cut. To fill both small and large gaps, start with the small gaps. Then, make a deeper cut in the tip, and fill the larger gaps second.
Similarly, there are two methods to pierce the seal of the caulk tube: using the seal punch tool that comes with the caulk gun or using a long nail. Once you’ve cut the caulk tube and pierced its seal, load the cartridge into the caulk gun.
Tip: If you’re a newbie, take a few passes on one of those Amazon boxes you haven’t recycled yet. This helps you get a feel for the caulk gun and lets you practice your technique.
Apply Caulk to the Window
- Tape off the area: If you’re messy like I am, putting some blue painter’s tape along the edges of the trim will help you get a straight line and keep the areas around it safe from spillage. (Using tape is not a necessity if you are confident in your skills.)
- Apply caulk in a smooth line: Hold the caulk gun at a 45-degree angle to the trim and press the trigger steadily for an even flow. Ensure a continuous bead to prevent breaks and water leaks; overlap any gaps.
- Avoid overfill: Adjust the pressure on the trigger for controlled application.
- Smooth the caulk: Use a smoothing tool or a soapy finger immediately after application to fill seams and achieve a neat finish.
- Remove the tape: If you applied the painter’s tape, take off the tape gently while the caulk is still wet.
- Clean up the mess: Tidy up any debris, tools, and equipment. Give yourself a round of applause for a job well done. Now, it’s time to allow the caulk to dry and cure.
Let the Caulk Dry and Cure
Refer to the manufacturer’s guidelines for the appropriate drying and curing times before handling or painting. Generally, it feels dry to the touch in about 24 hours. However, the caulk type, humidity, and temperature can affect the overall curing time.
Note: If there’s too much moisture or if the temperature suddenly changes, the caulk might crack or shrink before it’s completely set.
Check out this video to learn how to apply caulk around the interior side of a window:
If you need to caulk around the exterior side of a window to keep drafts, water, or pests at bay, this video shows you how:
Painting Over the Caulk
Before you paint over your caulk, ensure it has dried completely, according to the label’s instructions. If you paint over caulk too early, the paint may crack or peel. This happens because caulk usually shrinks as it dries, which causes the paint layer to stretch and ultimately break.
FAQ
Do Caulking Methods Differ by Window Type?
Yes. If the window sash is fixed (doesn’t move), you can use permanent caulk. If the window sash moves, use a temporary, semi-permanent caulk for seasonal insulation.
Here are some examples of the most common types of windows and how they open:
- Single-hung: Lower sash moves, but the upper sash remains fixed.
- Double-hung: Upper and lower sashes both move independently.
- Horizontal sliding: Sashes can slide horizontally from the left, right, or both directions.
Fixed sections and joints, such as those on the top of a single-hung window, can be caulked. Moving parts, such as those on both sashes of a double-hung window, should never be caulked with permanent caulk.
Consider using semi-permanent rope caulk on movable sashes, assuming they will be closed for a season (for example, for the winter). It’s considered semi-permanent because of its ability to adhere to your windows longer than weatherstripping tape. Yet, it can be easily removed whenever you want to open your windows again.
Pro Tip: Weep holes should always remain unsealed.
What are Some Common Window Caulking Mistakes?
Take my advice and avoid these common window caulking mistakes to extend the life of your caulk:
- Not cleaning and prepping the surface before caulking.
- Choosing the wrong type of caulk.
- Misjudging the amount of caulk to apply.
- Cutting the caulk tube incorrectly.
- Neglecting to smooth out the caulk.
How Often Should You Caulk Windows?
It’s a good plan to replace your window caulking every five years. But since weather can affect how well it holds up, check it twice a year — once before winter and once before spring.
During these checks, keep an eye out for the following signs that indicate it’s time to refresh the caulk on your windows:
- Peeling, cracking, or discoloration.
- Presence of mold or mildew.
- Small insects on the windowsills.
- Drafts, moisture, or condensation on the glass.
- Whistling sounds coming through the windows.
Caulk to Keep a Comfortable Home
Looking back on the moments when I watched my dad caulk our windows, I now appreciate that crafting a smooth bead takes practice and patience. So take your time as you clean the area, apply and smooth the caulk, and wipe away any excess. If you do, you’ll likely achieve a polished-looking, effective seal that will keep your home cozy and comfortable.
If you love the idea of caulking but don’t have the time or lack the skills, it’s time to hire a handyman service. They’ll be able to seal up your windows in a snap.
Note: Home Gnome may get a referral fee for matching you with handymen in your area.
Main Image Credit: Africa Studio / Adobe Stock Free / License
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