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How to Caulk Siding (and How Not to do it)

All types of siding are effective at protecting your house from the elements, but they can’t protect what they don’t cover. Moisture can still seep in at butt joints (the places where the ends of two pieces of siding meet) and where siding meets trim. To avoid leakage, these seams should be sealed with caulk.

Caulking your home’s siding is a simple process, but not necessarily a foolproof one. Caulk is by necessity a sticky, gooey substance, and as such it smudges easily. And many homeowners over-caulk, applying caulk where it doesn’t belong and potentially compromising the performance of their siding. To do the job properly, you need the right equipment, the right technique, and the right plan.

Materials: What You Need

You can probably buy a caulking gun for only a few dollars. You should buy one for a few dollars more. Cheap caulking guns create as much work as they perform in the form of messes that need to be promptly cleaned up. Plan on spending $10 or more for a high quality caulking gun, one that will dispense caulk steadily and predictably. The aggravation you save is more than worth the extra money. When choosing caulk, make sure you get one that is specifically for exterior use, that will bond to your type of siding, and that is paintable. The only other tool you need is a sponge.

Getting Started

Caulk needs to be applied to a clean, dry surface, so your first step is to wash the areas you will be caulking with soapy water and a sponge. Ideally you should do this a day ahead to ensure everything has plenty of time to dry. After putting a tube of caulk into the gun, cut the very tip of the tube off with a razor. Continue slicing small pieces away so you can make sure you don’t cut off too much–you want the hole at the end of the tube to be the same width as the gaps you will be caulking. Often this means you will need to use different tubes of caulk at the butt joints and where your siding meets trim.

Squeeze, Wipe, Sponge, Repeat

Working fairly small areas at a time, squeeze a bead of caulk into a seam, run your finger over the caulk to smooth it, and then run a lightly damp sponge over it to smooth it even further. Repeat the process until you’re done.

Don’t Overdo It

Finally, it’s important to know where to caulk, and where not to caulk. Water can seep in around butt joints and trim, so these areas need to be caulked. You can also use caulk to repair cracks in your siding. Do not caulk the underside of your siding (i.e., caulk each piece of siding to the one beneath it). Your house’s siding naturally expands and contracts, and caulking it all together prevents this movement.

About the Author: Brett Freeman is a freelance journalist who writes for ReliableRemodeler.com, a nationwide contractor matching service working to bring together homeowners and local contractors for free estimates on home improvement projects. He also owns a landscaping and irrigation company in North Carolina. Previously he has worked as a beat reporter, a teacher, and for a home improvement company.

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