Finally, good all-around caulk. Sikaflex-1a ($34 for 6 tubes) is a premium-grade, high-performance, moisture-cured, one-component, polyurethane-based, non-sag elastomeric sealant. It is simply the best there is for the money. I’ve used it for the past 10 years to seal windows, doors, siding and cracks in masonry. It is what silicone should be. It stays completely flexible and is paintable and easy to work with. It comes in many colors and is relatively cheap. The only disadvantage it has is that it can’t be sanded.
Other caulk is either difficult to work with, sags or degrades over time. Silicone is especially frustrating. I’ve had to dig it out after a few years of exposure to the weather as it loses its adhesion and no longer provides waterproof protection. Goodbye silicone, hello Sikaflex.10/27/18
(This is a Cool Tools Favorite from 2009 — editors)