If your gutters are dry and clean, then pretty much any caulk will stick to them. But if you choose your caulk wisely, it will last a long time. If you choose poorly, the caulk will get harder with time and won’t be able to expand and contract as the outside temperature fluctuates. With that in mind, let’s take a look at some of the options available for fixing leaks in your gutter system.
Urethane Caulks
Urethane-grade OSI caulk is a great choice for contractors repairing gutter systems. They aren’t based on silicone, but rather on urethanes and polyurethane composites. They have many of the great qualities of silicone caulk—they last a long time, and are resistant to UV light. They also don’t smell as strongly as silicone caulks. They cure at a fast rate, and are easily paintable. Some polyurethanes are moisture-curing. This means they can be applied even if the gutters have a bit of moisture, as the water causes the caulk to form a flexible bond.
Butyl Rubber Caulks
Butyl rubber caulks work very well for fixing gutter leaks. It can be applied whether it’s hot or cold outride. It sticks quickly, but remains flexible after it cures. Changes in temperature will cause the gutters to expand and contract, and this caulk will move with the gutter as it does this. The seal will also remain watertight.
Polymer Caulks
Polymer caulking is also an excellent choice, both for gutter repairs as well as sealing new gutter systems. One brand, called CT1 Sealant, contains no solvents. Because of this, the caulk doesn’t shrink when it cures. Polymer caulks are ideal for PVC as well as aluminum gutter systems. Because they have multiple uses, polymer caulks are ideal for professionals, even though they are more expensive than butyl rubber caulks.
Silicone Caulk – Not Recommended
When repairing gutter systems, it’s best to avoid using silicone caulk. While it sticks well and forms a watertight seal, it can’t be painted. Also, once it cures, nothing will stick to it. This means that if a joint needs to be repaired again, the whole seam needs to be torn apart and all the silicone caulk must be removed before new caulk can be applied. For these reasons, we feel that silicone caulk is not a good choice for making gutter repairs.