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Quick Tip: When to Use Spackling and When to Use Caulk on Moldings

Beware of Shrinkage!

how to paint moldings

A small gap like this on can be filled with caulk because it is so small.

[This is part of my How to Paint Moldings series.]

When to Use Caulk

Use caulk on very small gaps or holes, because caulk will shrink a bit when it dries.

That shrinkage will leave a slight cup on the surface of the caulk.  And that’s OK for these small gaps and holes, but it’s not OK for filling larger gaps where the filler needs to hold its shape.

Also, caulk can’t be sanded, so don’t put it anyplace that will be worked over by sandpaper.

See the kind of caulk I use here >>

how to caulk moldings and millwork

This small gap between wall and molding can be filled with caulk.


When to Use Spackling

Besides using spackling to fill nail holes on your molding, use it to fill gaps where you need the filler to hold its shape.

Just as important, use it where you’ll need to shape the filler after it has dried, like in the example below.

how to paint moldings and millwork

A gap this wide should be filled with spackling so that it can be shaped and sanded.

Above  This is the same section of vertical wall frame as pictured at the top of this post.

The gap is wide enough at this point that I want to fill it with spackling so that I can shape it into a nice ninety degree angle after the spackling is dry.

Below  Even though this gap is pretty small, I’m going to fill it with spackling instead of caulk.

Because when it’s finished, I want that gap to look like it’s part of the molding.

See the kind of spackling I use here >>

how to paint moldings

A bow in the wall creates a large gap that will be filled with spackling.

Fast and Slow Methods

Caulking gaps and holes is much faster than filling those same spaces with spackling.

So save yourself a lot of extra work by learning the best use for each kind of filler.  All it takes is a little practice and you’ll be a spackling and sanding pro in no time!

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9 Responses to Quick Tip: When to Use Spackling and When to Use Caulk on Moldings

  1. Aleece January 9, 2013 at 5:59 PM #

    Ken – thanks for the inspiration! With the aid of your blog, we just added entablatures and trim to our 4 living room windows and are completely wowed by the results.

    Just curious about your thoughts on spackle vs. wood filler.

  2. Ken January 10, 2013 at 11:22 AM #

    That’s so nice to hear that our blog inspired your entablatures, Aleece! Do you plan on installing even more moldings now?

    I’ve only used wood filler a few times. Wood filler is thicker, making it harder to cram into tight corners, and it’s also harder to sand into the shape I want. But wood filler is perfectly fine for moldings. Just be sure it gets a good coat of primer over it before sanding.

    Good luck on your next molding project!

  3. Brad January 22, 2013 at 12:58 PM #


    I installed crown molding in the bedroom of my last house and I used spackling between the joints. The expanding and contracting of the long boards sent a crack down each seam and bothered me every winter.

    I have since purchased a new house in desperate need of trim upgrades everywhere. I have recently started the plunge but have been exclusively using caulking because those cracks still haunt me and I feel caulks flexibility will prevent them. Can you address expansion and contraction?

  4. Ken January 22, 2013 at 2:50 PM #

    Hi Brad,

    Moldings, like anything else attatched to your home, will need periodic maintenance. Sometimes that means regular rounds of seasonal caulking.

    That said, here is a post that deals with the primary reason crown moldings separate at the joints: Why I Don’t Install One-Piece Crown Moldings.

    When I have a crown molding joint that opens up each season, I’ll use a caulk with higher silicone content like DAP’s Dynaflex 230. It may not solve the problem permanently, but it usually does a better job than painter’s caulk in this situation.

    Good luck with your new project Brad!

  5. Brad January 23, 2013 at 11:10 AM #

    Thanks Ken, I read your crown molding post and it answers a lot of questions for me. Also your crown design has won another fan, I’ll add it to my plans.

  6. Brad February 1, 2013 at 6:32 AM #


    Ok so I’m in the middle of my project and will switch over to spackling. I am curious about why you spackle before priming but caulk after priming? If primer fills a gap do you consider that gap filled and move on? Also, when you cut trim pieces in the dry winter, do you plan for any gap or do you cut as close as possible? I live in the northeast so the temperature and humidity changes concern me. I am learning a ton by racking up my mistake list but so far it is still looking good. Thanks!

  7. Ken February 2, 2013 at 9:38 AM #

    1. You can’t sand caulk, and that’s why I caulk after priming. Also, I use a wet finger and a wet rag to work with the caulk and I don’t want the water to get on the bare maaterial.

    2. If primer fills the gap, then I leave it. If not, I fill it with caulk or spackling.

    3. The reason I glue every single contact surfact on every single modling I install is to combate expanding or contracting joints. You do your best, and then if a joint opens up you can just re-caulk/paint it. Some joints may need regular maintenance, but I always shoot for a 100% rock-solid installation.

    That’s why stained woodwork is more expensive and complex to install. You must use high-grade materials and more advanced joinery techniques to allow for expansion and contraction over time.

    Most of the patterns on our site were installed in the northeast as well, and they still look great today.

  8. Brad February 3, 2013 at 3:55 AM #

    Duh, your caulking answer is pretty obvious now and makes complete sense.

    I have noticed how liberal you are with adhesive and I understand your reasoning now. I will make sure it is a priority for me going forward.


  9. Ken February 3, 2013 at 5:27 AM #

    Good luck Brad!

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