Caulking the Interior of New Windows

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How to use a caulking gun and how to caulk new windows TwoPlusCute

We are finishing up the new window of the nursery, now that we fixed the missing drip cap. Once a window is installed, the next step is to seal it properly. And the next-next step is to tackle the rest of our non-closing, non-opening, old windows.

Especially the one I caved in with my thumb. Long story but it was so rotten I pushed through the wood, with just my finger…

In this post however, we are sharing how and where to caulk the interior of newly installed windows.

We will also demonstrate a caulking gun (a good caulking gun – mom pay attention!) and how to use it. There is a LOT of information in this post so get the beverage of your choice and read on!


This post contains affiliate links. Read our disclosure policy here.


Why Caulk?

Caulking presents several benefits: it protects against drafts and it is a very effective in weatherproofing and winterizing a house.

Sealing against drafts is also a green practice as it helps the heating or cooling elements of your home, perform better with less effort due to smaller temperature loss through any gaps.

It also helps hide unsightly gaps between different elements, from floors to trim, creating beautiful end results. From bookcases to tile, caulk is the magic fairy dust that makes everything prettier.


We need a Cheat Sheet

The following photo helps as a cheat sheet for the terms I use in this post. Some poetic freedom was used; you may know the parts under different names. Hope the photo helps make some sense of this post. 🙂


Caulking gun parts, how to caulk windows TwoPlusCute
Cheat sheet with the terms I use in this post (so I make a bit of sense). No7 is also called a “barrel” or a “cradle”.


Choosing the right caulk:

1. Silicone over acrylic

Silicone caulk is expandable and fares better than acrylic caulk with materials that are flexible by nature and susceptible to weather changes. Wood and vinyl expand and contract a lot, depending on the seasonal temperature and moisture levels. Similar to no 4, hybrid caulks with silicone characteristics exist for every particular application.

2. Paintable

It is easy to remove beads of caulk, it less easy – and pretty tedious – to remove flattened dried silicone. If you had to overcaulk a spot, like a hole for example, using paintable silicone will make your life easier and the patch invisible.

Did you know caulk comes pre-colored as well?

3. White vs Transparent

While we mostly use white ones, transparent silicone is great for projects where you plan to paint only one side of a project. For example, where the trim meets the wall, you may want to avoid re-painting a finished wall.

4. Interior, Exterior or both

In the past, exterior silicone usually had UV inhibitors to withstand direct sun, was waterproof but not paintable. Now, there are hybrid latex/silicone caulks that are waterproof, weather resistant and paintable. They can be used for both indoor and outdoor projects.


The Caulking Gun:

A good caulking gun is sturdy and has built in amenities like a tube cutter and a long pin to pierce through the tube opening. In short, it has everything to make our caulking lives easy.

  • A sturdy caulking gun, does not rattle and feels solid. That actually helps for applying a perfect bead.
  • The piercing pin is used when we first open a caulk tube and when we need to re-open the hole of a used tube where the silicone has dried. A long nail can do the same job, if you are feeling like carrying extra nails around.
  • The cutter, cuts tube nozzles like they are…butter – it’s an extremely effective cutter; better than scissors. Drive the nozzle in gradually – so you cut the opening as big or as small as you want.

CAUTION: the hole is big enough to fit child fingers (and my pinky for that matter). Do not leave the gun where young children can reach it.

True story: On occasion I have performed my comic dance act of “why isn’t the  @%*&  caulk comin’ out?”  – where I used all my strength to squeeze caulk out, jumping on the spot, to no avail.

Caulk tubes have a seal to keep the silicone wet that sits, deep in the neck of the silicone tube. If you have made your cut, put the tube in the gun and squeezed real hard but nothing comes out, use the pin and puncture the seal by driving it ALL the way in. No half measures there.


How to load the caulking tube TwoPlusCute


How to release the safety in order to load the tube:

Press the silver safety (what I am pressing with my thumb), holding only the handle I am holding in the photo and not the trigger part. Pull the extender all the way out with your other hand.

Slide the tube in the tube cradle and either push the extender in while you are pressing the safety or simply hold the trigger and pump until it’s tightly snug.


How to Apply the Caulk:

You can cut an angled hole using the cutter. It is not necessary but seems to help a lot of people (me included) to drive the bead better against the gaps.

Push the trigger half way, until you see the size you are aiming for a cut and then insert the nozzle through the cutter hole and cut.


Using the built in cutter to cut the nozzle open, driving the nozzle in an angle TwoPlusCute


Go from inside to outside from top to bottom and in that order (first the inside area from top to bottom, next the outer area from top to bottom). While it is not a life-saving tip, it does make it easier to avoid leaning against already caulked areas.

Work with controlled speed. The caulk will actually “tell” how fast to go: if it is a straight, un-broken line, the speed is perfect. If it breaks on the way, you are going too fast. Hold the gun in an angle against the gap – and if you are really awesome try to hold it at a 45 degrees angle like some robots with highly advanced accuracy people suggest.

For certain applications, it helps using painter’s tape to outline (and keep it contained), while creating a perfectly straight line. Such uses include caulking the base of a bathtub (where it meets the floor), or where kitchen tile meets the countertop.

However, I find that using tape for window caulking is more trouble than help – other people may have a different opinion of course. Do what feels best to you!


Applying caulk in new windows TwoPlusCute
Messy fingers, big heart people! (And lots of scrubbing afterward…)


The order I go about for least mess is as follows:

First I caulk the inside, where the window frame touches the window, starting from the top.

Then I seal the seams of the frame and where the frame meets the trim.

Finally, I caulk the perimeter of the trim, where it meets the wall.


Work in sections and smooth the beads with a wet finger. Run your finger tightly over the silicone bead. That forces the caulk into the gaps and removes the excess. Use a very wet paper towel to keep your finger clean and constantly wet. Or do it the male way and spit on your finger as you go but, I am a – powertools brandishing – lady and use a wet rug instead.

There are mini tools to help in creating a smooth bead and I do use one I bought in a home improvement store for under $5. I use my wet finger first and finish up with the tool. Producing pretty invisible seams:


Caulking a new window TwoPlusCute
Top image: no caulk yet – Middle image: caulk bead applied against the vinyl window – Bottom image: Caulk smoothed out.


Hubby used the mini caulking tool for an exterior flat seam and says it’s the best invention after fire. I must admit it helps create perfect seams.

Here is the one we have. The allway tool and the dap-pro are also good and low cost options.


Remember: It is easy to fix the silicone while it is still wet, either by using your finger or a wet sponge. Once dried though, it’s a whole different story. Well, you can still use a wet rug and rub it but won’t be as smooth.

Before painting, wait for the caulk to cure (usually 2- 4 hours – but read the instructions). Make absolutely certain you have created a perfectly flat seal because, every lump will be ultra visible once you paint.


Storing Away:

Once done, clean with a wet rag or paper towel and hide the caulking gun far from children’s reach.


Nail in to keep the nozzle open before storing a caulking tube TwoPlusCute


Tip & Trick:  If you still have caulk left in the tube, clean the nozzle with a wet rag, then find a long nail or screw the size of the hole and close the tube with it. Some sealants come with a cap but – speaking from experience – it’s a hit or miss to keep the silicone wet and the nozzle clean. My father in law insists on using nails and never screws because the ribs of the screw, trap air inside and dry the silicone. I didn’t listen once. He was right. Only nails, people!

Use a nail even if your tube came with a cap. When you need to re-use the tube, pulling out the screw will also remove the dried silicone and will open up the nozzle.


Bonus: where to tape before you paint your window trim.

Once the caulk has dried, it’s time to put some painter’s tape and paint the trim. You can use the tape, as shown in the following picture, when you are adding the silicone, too – if you feel it will make your work easier.


Where to apply painter's tape when painting a vinyl window TwoPlusCute


That is the easy part, go all around the trim, where it meets the wall. Then cover the interior face of the window with the tape ( I think it’s called a sill?). In our case it is a vinyl window and we don’t want paint on it at all so we cover with tape.

If your windows are double hung like ours, slide down the top sash and throw a large piece of paper or a sheet over it. Slide back up to lock it in place to protect your windows from paint droplets. Alternatively you can use more tape and stick the paper in place. It’s an easy way to ensure minimal clean up and avoid scraping paint of the glass.


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This window is in our nursery. I am happy to report it looks gorgeous (and shiny and clean) all finished and painted and am even happier that – besides removing the painter’s tape and the paper – I had to do exactly zero cleaning.

None whatsoever.

Loved that part. 😀


More on windows:

How to remove a window

Step by step how to install a new construction window

And something utterly different (but pretty) to surprise you.

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15 thoughts on “Caulking the Interior of New Windows

  • July 7, 2017 at 12:37 pm

    It’s good to know that there are pre-tinted caulk products out there! That definitely takes a step out of the process. Thanks for sharing your tutorial!

  • December 21, 2016 at 2:18 pm

    You have a good point about weather proofing. Caulking has many benefits.

  • May 16, 2016 at 3:59 pm

    Great job! I was just talking to the hubs about this the other day. We installed french doors 20 years ago and then added foam in the spaces but we never added caulking. It never ends.

    • February 28, 2017 at 2:57 pm

      True, it doesn’t end. And sometimes, we have to re-caulk after a few years. But at least caulk has the benefits of both better looks and lower utility bills. Win win. ^^

  • May 9, 2016 at 5:24 am

    My husband has a gadget just like that and there is no way he’d let me within a mile of it, and I really don’t know why… Probably because I’d be that person jumping round trying to squeeze the contents out and not having much success.

    Love your guide though. If ever my other half leaves, I know where to come for help!


  • May 7, 2016 at 6:27 pm

    You did an amazing job…..really neat. It was a great tutorial……very hard not to do it right after that.
    Oh, Lordy, does that bring back memories! Our home was built in 1927 and had original windows which I loved….there were three vertical panes on top. But, they were inefficient and we replaced them. Try as I did, I couldn’t stop progress!!

    • May 14, 2016 at 1:41 pm

      We had wasps coming in the baby’s room through the old windows!
      It was high time we put something more efficient energy wise and solid. 🙂

  • May 7, 2016 at 7:16 am

    Excellent post! Caulking and I have a love/hate relationship. I love the finished look and hate the work! LOL You remindede me I haven’t finished caulking all my baseboards yet… *sigh* Pinned!

    • May 7, 2016 at 12:22 pm

      You guys did a great job installing the baseboards!
      Thank you for the pin. 🙂

  • May 6, 2016 at 5:03 pm

    Very practical and helpful info! Pinning for future reference! 🙂


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