Caulking
Learn the Tools, Techniques and Products to Get Professional Looking Results that Last
In this weekly Q&A column, retired builder/building inspector Cam Allen answers readers’ questions about home renovation and climate resilient homes. Have a question? Enter it in the form below.
During a visit to my local hardware store recently the store manager stopped me with a question. “Why do most homeowners not get the drift of the importance of a proper caulking application? . He went on to say most customers buy the cheapest caulking gun and any budget caulk and then are upset that the project turns into a mess. Caulking is one of the most important home maintenance projects – based upon one CMHC survey, air sealing (of which caulking ranks number one on the list) can reduce heating and cooling costs by upwards of 15 to 20 percent.
It’s true that there is a different caulking for nearly every project today and it can be confusing. This is a quick list and then I am going to provide an experience based list of tips.
- Acrylic latex and siliconized acrylic, is also known as painters caulk. Good for any interior gaps, easy to apply, cleans up with water and is paintable.
- Siliconized does have some water resistance – 100 percent silicone is best used for kitchen and bathroom applications as it is completely waterproof, mould resistant and flexible.
- Polyurethane or simply urethane has many exterior applications when concrete, masonry and roofing is involved.
- Hybrid polymer has excellent multi-surface applications both inside and outside and is extremely flexible.
- Butyl rubber is used for roofing, eavestrough and some exterior metal sealing.
- Asphalt caulk is another roof seal, mainly for conventional shingles.
Now onto the most common caulking issues and the number one cause for caulking failure is lack of surface preparation, mainly by not removing the old, cracked caulk and cleaning the surface. The next most important step is having the right tools. Yes, I know it’s a time consuming, messy job but with the invention of battery powered oscillating tools this job has become a lot quicker and neater. Using the standard wide blade or a wallpaper blade this tool is the answer for removing most caulking. A half decent model is now available for under $100 and it has many other uses.
Most come with a sanding pad for smoothing the surface once you have cut the old caulking away. The other “must have” is a set of hand profiler tools. These have become popular in the past few years to give your caulking efforts a professional finish.
The next step once the caulking is removed is surface preparation and unless it’s done right, you will waste all your removal efforts. The surface where the caulk is going to be applied must be clean, smooth, dry and not porous in any manner. A coat of good oil based primer, allowed to fully dry is never a wrong move.
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The next step is properly injecting the caulking at the right bead size. But before you go there, if you have a joint that is wider than a ½”, is an outside joint or is a joint between different materials then you should be using a product called “backer rod” first. This flexible foam cord is inserted into a joint before caulking is applied. It should fit firmly but not compressed. There are two kinds, open and closed cell with the closed cell being the firmest and best for wider joints. We used a piece of wooden dowel with one end shaped with a
concave cut to fit the backer rod into the gap. The most important step is trying to fit the backer rod to the same depth. We found ¼-⅜” was the best depth before caulking. We measured and marked the dowel with a magic marker at ¼ inch and ⅜”.
Now back to the actual caulking application. Do not over-cut the nozzle, if your gaps are ¼” on average then a 45 degree cut of the nozzle at approximately ⅛” is a general rule of thumb. Now lets look at your caulking gun and every time I see one of the $10.99 models I chuckle. Spend the money on a good, dripless or rat-rod style gun. The gun should have a thrust ratio of 10:1 or higher. We used
caulking guns with an 18:1 thrust ratio for a smooth even feed of the caulking flow from the tube. The better guns come with an attached rod for clearing the thin plastic cover inside the nozzle once you cut the tip. This type of gun also has a revolving frame to allow you to adjust the bead as you are applying the caulk. The tube rod is bent to allow you to hang the gun securely onto a ladder step, cheaper ones are bent in a 90° and constantly fall off the ladder. Expect to spend over $30 for a good gun. It should last you a lifetime and make your job a lot easier.
Another tip when applying caulking is understanding the right technique. Most interior caulking is a smaller joint with a background like tile over waterproof backer board or trim over drywall. For interior caulking, push the caulking gun bead ahead of the nozzle cut at 45°, then go over with your profiler tool that you have checked is the right size. Then remove the excess with a damp cloth.
For exterior caulking, pull the gun towards you and watch the level of caulking that the gun is dispensing. Apply even pressure on the trigger and move the gun at a steady, constant speed. Overlap any joints by about ¼” when you have to start a fresh tube of caulking, your profiler tool will fix this joint.
Lastly most homeowners make the effort to caulk around windows and doors but there are areas that are often missed. If you have access to the plate area where your building frame is attached to your foundation, caulk this joint. The threshold at your doors, get underneath the plate. Any exterior openings like the vents for a high efficiency furnace, dryer vent and exterior electrical boxes.
Remember, upwards of 75 percent of all caulking jobs fail due to poor surface preparation. Lastly, allow full cure time before you paint your caulking and use a recognized brand of primer applied with a brush.
Caulking is a time consuming process. Done right it should last at least 15 to 20 years if you use a high grade urethane or polymer caulk for the exterior. The days of caulking only lasting 6 to 8 years are gone if done properly.
Images from Depositphotos
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