Use Lightweight Spackle to Fix Molding Gaps

I am LOVING my crown molding templates!  They make installing crown molding so much easier. I just can’t believe that Sandra didn’t tip me off to that little trick a few years ago when I was installing 500 sf of crown molding. Come on, help a sister out!

Use light weight spackle to fix molding gaps

But even with Sandra’s easy templates, getting perfect corners can still be a challenge.  Walls and ceilings are frequently out of square, and then there are vaulted ceilings, dah, dah, daaaaaaah (cue scary music)!  Let’s face it, sometimes gaps happen. So for those times when your moldings don’t line up perfectly and you have gaps, lightweight spackle can be an easy fix. Note: This is for painted moldings only. If you have wood molding that you are going to stain, this is not the fix for you.


My upstairs bath has a sort of wonky double sloped ceiling. I experimented with a couple of techniques to install crown on a vaulted ceiling, transition pieces and corner blocks, but my vault is so mild that they just looked odd. I decided to force the corners by altering the spring angle and ripping a new bevel angle. This worked out great on the inside corners, but the outside corners were another story! After a couple of hours of running complicated mathematical models (OK I used a pre-made spread sheet), making test cuts, and about 10 feet of wasted crown, I used the test angles that fit the best and knew that I was just going to have to fix the cracks. I am a bit uncomfortable exposing my bare crack in public, but here goes:

light weight spackle to fix gaps

I know, Scary, but with a little caulk and light weight spackle, no one will ever know. OK I guess everyone who sees these pics will know, but you get the idea.

Start by caulking the molding as per usual, and include a bead of caulk in the gap. This will stabilize the molding. Don’t worry about trying for a cosmetic fix with the caulk, just fill the void and let dry.

Dap light weight spackle to fix molding gaps

Next use lightweight spackle, I like Dap’s Patch –n- Paint. It has the texture of a stiff meringue and seems like it will be too delicate to work, but this stuff is awesome!  It is moldable (OK it’s not modeling clay, but you can get it to conform to a molding profile pretty easy), and the edge can be feathered to blend really well. It is sandable, but retains a bit of flexibility so it won’t crack and chip out over time, and it doesn’t shrink.

light weight spackle to fix molding gaps

I start by making a series of small balls or snakes that I press into the gap leaving the spackle proud. Then gently blend. Work quickly, as the spackle dries it will begin to stick to your fingers and is less toolable. Don’t try for perfection just the general shape and let dry. After the patch has dried use sandpaper to continue tooling and refining the patch. Repeat until you are happy with the look. If the spackle you are using needs to be primed it is a good idea to prime between coats so that you don’t re-imulsify the first coat as you add more. Dap’s Patch-n-Paint doesn’t need to be primed, Hallelujah for one less step!

Now paint your moldings and watch that ugly gap disappear! Is it perfect? NO, but as long as no one is going to be looking at your molding with a telephoto lens, it is pretty darn good!



  1. Hello I Live Here - Linda says:

    That’s one awesome fix!!! Great job!

  2. Candice Hofmann says:

    Loved this post! It reminds of what my wonderful Uncle Frank always said: “Putty and paint fixes what ain’t”. I always say that to myself when doing a project with molding that doesn’t come out perfect! BTW, this led me to your great tutorial on cutting crown moldings. I bookmarked this so I can use it in the future! Thanks!

    • That’s cute, I have heard a version about make-up fixing what “ain’t.” I like your uncle’s much better!

  3. Great tip! I’m always filling molding cracks and this tip makes them disappear!

  4. it is always interesting to see the imperfections we find in our projects become ‘perfect’. thanks for the info, i am sure i will use it sometime in the future

  5. Perfect timing as we have yet to caulk and paint our board and batten installed Thanksgiving week. Yes, it will be a fun Christmas break! This will help wonderfully on the wonky stairs in our 60′s tri level. This project was like completing a puzzle at times! This will be great for the few trouble spots we couldn’t “perfect”–ha! Thanks!

  6. That is incredible! Never thought to sand spackle – thanks for sharing!