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Should You Caulk Butt Joints On Siding? The Answer Might Surprise You.

Caulk Cracks At Butt Joints Are No Joke (although saying that is pretty hilarious).

Cracked caulking in the butt joints of your siding happens every year, but what can you do about it? Here are some great caulking tips.

Example of cracked caulk at a siding butt joint.
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Why It Happens

Proper caulking joint design
Proper caulking joint design

Butt joints are a perfect example of poor joint design. They’re too small to accommodate a bond breaker (backer rod), so the caulk can’t stretch properly once applied. But they’re also too large to simply leave alone. A lot of moisture from rain, snow, misdirected sprinklers, or even an epic summer water fight can get in – enough to do some serious and expensive damage.


So what’s the solution?

The short answer: keep caulking them.

The Bad News

Unless you plan on removing the siding and installing joint flashing, there is no way around regular maintenance on siding butt joints. Those joints need to be protected.

The Good News

Sashco’s high-performance sealants, including Big Stretch®, Lexel®, and eXact color®, consistently out-perform standard caulking products found in stores. Every Sashco product is specifically formulated with superior elasticity and adhesion to stretch and hold over the long-haul, even in less-than-ideal circumstances (like butt joints). This means you can delay the inevitable a bit longer, saving you time and money.

BONUS: All of Sashco’s products stick to themselves. This means that you won’t have to completely remove the cracked caulking every time those butt joints need to be maintained. You can simply apply more caulk right on top.

So, caulk ’em and maintain ’em, and save yourself time, money, and your sanity –
no if’s, and’s or *ahem* butts about it. 

Watch this video to learn more about the butt joints on Hardie planks or lap siding.

See Also:

Side note: this applies to existing homes.  These days, most manufacturers have come out with recommendations when new siding is installed, most of which require flashing behind those joints in order to maintain a warranty. If you’re in the market for new siding, make sure they have a solution for those butt joints included in the installation instructions