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Should You Caulk Siding Butt Joints? Read This!

Cracked Caulk At Butt Joints Is No Joke

It happens year after year: cracked caulking in the butt joints of your siding. But what can you do about it? Here are some great caulking tips.

Example of cracked caulk at a siding butt joint. Photo Source:


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 exuberant water fights can get in there – enough to do some serious and expensive damage.




So what’s the solution?

The short answer: keep caulking them.

The Bad News

The bad news: there’s no way around regular maintenance of those siding butt joints, unless you want to completely remove the siding and install joint flashing. Those joints need to be protected somehow.

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 over top.

So, caulk ’em and maintain ’em, and save yourself time, money, and your sanity –
no ifs, ands 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