A good caulk job can make or break a project. Whether it’s cosmetic issues on baseboards or water penetration on window sills everyone needs to know how to accomplish the 4 secrets to perfect caulk. I have seen more projects damaged by improper caulking than I can count so I feel like it’s high time I addressed this topic on this blog.
Before we get into technique, I should start with the understanding that you have to use the right caulk for the right job. I’ve written extensively on How To Pick the Right Caulk and you can read my suggestions there before you grab just any tube off the shelf. Even if you use these secretes below but don’t use the right kind of caulk you’ll be stuck with a failing caulk job in a short time. So, read that first if you have any doubts about what the right product is.
1. Cutting the Nozzle Properly
This secret is what screws up more people than anything else. There is a wrong way and a right way to cut the nozzle on a tube of caulk and it depends on the project. Cutting a caulk nozzle can be done a number of ways and you need to know which way is most conducive to the size and shape of the joint your are filling. Here’s my rules for cutting the nozzle:
- Always use a sharp razor knife, NOT the cutter on the caulk gun – That cutter is designed to make your life miserable. It never cuts properly and things are sure to be a mess if you use this stupid thing.
- Cut at a slight angle – I prefer cutting the nozzle at a 60º angle in a perfect world, but any angel is better than cutting it flat.
- Cut the nozzle about 10% larger – This is pretty straight forward. Don’t cut a wide nozzle for a small gap or a small nozzle for a wide gap. Your cut should allow for an opening just about 10% wider than the gap you are filling so there is some overflow onto the sides of the gap to provide bonding
- Bevel the tip using a sanding block – This one is often missed, but if you are caulking a typical 90º joint then sanding the edges down so the tip of the nozzle runs right in that groove will keep your caulk line from wandering
2. Use a Dripless Caulk Gun
Caulk guns have come a long way in the last decade. If you are buying a cheapo caulk gun you will get a cheapo caulk job. And we’re aiming for a perfect caulk job, right? A dripless caulk gun is one that triggers firmly and evenly but also releases pressure on the plugger when you let go of the trigger so the flow of caulk stops when you do.
This helps avoid drips and spills but also doesn’t make you do the whole “catch the drip with your finger” and “use your finger as a caulk gun” thing we all hate. Buy a premium dripless caulk gun and you can be sure of premium results for your caulking work.
3. Caulk at the Correct Angle
Remember that angle you cut on the nozzle? Well, it’s time to put that angle to actions. If you pull your caulk gun along at a very steep angle the caulk will squeeze out and make a mess. If you pull along the opposite, a very flat angle, then the caulk won’t be pushed into the joint and won’t stick to the surface.
The best way to apply caulk is to apply at about a 40-60º angle by pulling the gun along rather than pushing it. This forces the caulk into the joint and doesn’t make a mess with squeeze out on the sides.
4. Use Backer Rod
If you are caulking a large joint (over 1/4” wide) then you’ll likely need to use something called backer rod. Backer rod looks like a small pool noodle and it comes in various sizes to accommodate various size joints.
When you have these large joints or joints where there isn’t anything behind the caulk joint to stop the caulk from disappearing into a void then this is an absolute necessity to give the caulk something to rest against and avoid pouring tubes and tubes of caulk down an empty hole.
How about one more tip for a perfect caulk job? If you’re using a water-based caulk use a wet finger to tool the finished line to perfection. If it’s a solvent-based caulk, then mineral spirits or paint thinner will do the job nicely for helping you smooth out the caulk line. This finishing touch will leave you with a caulk job even the pros will be impressed with.
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I love old houses, working with my hands, and teaching others the excitment of doing it yourself! Everything is teachable if you only give it the chance.
Great tips!
I also keep a can of inexpensive wet wipes handy as they do a good job of removing caulk from hands.
Also remember to check if the caulk is paintable. If it doesn’t say paintable somewhere on the tube, then it’s not and paint will bead up and peel off.
Thanks for this caulk tutorial!
I’ve done a lot of caulking over the years. However, I haven’t found the perfect caulk gun. Too many are a bit awkward, too bulky, or are difficult to use in tighter areas. Do you have any recommendations? Thanks again!
Please note the expiration dates on silicone caulk! I used an unopened silicone caulk tube from an earlier job which was a year past expiration; it came out like new but never dried. I didn’t even know there were expiration dates so didn’t figure out the problem until the next day, when guests were due to arrive. I went to check my beautiful newly caulked shower. It was as soft and wet as when I applied it. Required a messy cleanup and re-caulking with a fresh tube.
Your comment about using a wet finger to lubricate it is a great one. I have done thousands of hours of caulking on several houses. I take a small can and put water in it to lubricate my finger. I dip my finger in the water periodically and after finger trawling if my finger has caulk on it I scrape it off on the edge of the can keeping my finger relatively clean. It takes too many rags or paper towels to keep your finger clean. The can method works really well. By wetting your finger you can get the caulk joints small as smooth as you like so it doesn’t show.
Thank you Scott! I hadn’t heard of the no-drip type caulking guns and will definitely find one. I have a problem with the exterior of my 1908 home, made of hand-cast block. In some places around the windows the mortar has fallen out, some gaps are rather large. The previous owners tried to fill these gaps with some sort of cheap caulk. I will be using the backing rod for the larger areas, but am wondering if I should use a caulk to seal around the windows or mortar? Any advice is appreciated! BTW, backing rod in its many sizes is used by taxidermists for bird necking material 🙂