Frequently Asked Questions- Sealants
What is the best sealant to use?
We prefer 1-part urethane sealant in most applications. We generally don't recommend  silicone, solvent based caulks, or latex-based caulks. Solvent-based caulks typically shrink, become brittle, and crack.   
What is caulk?
Caulking is a generic term referring to a a liquid or paste that is used to seal a joint between two parts. The caulk can be made from many different base products. Silicone, solvent/filler, latex, etc. Polyurethane sealant is a superior caulking material.
What is polyurethane sealant?
Polyurethane sealant is a high performance, high adhesion type of caulking compound that has the potential to outlast and outseal other chemistries. It does not shrink and dry out.
How can i tell if my caulking is good?
Visual cues are missing caulk, cracks, dried gaskets, staining, etc. The best way to test for leaks is by performing a "blower door test".
What is butyl tape?
Butyl tape is a pliable putty filler with a high solvent (butyl) content. These tapes are typically used under window frames and trim strips. They have little adhesive quality, and are prone to drying out and shrinking. 
Can I just run a bead of caulk over the original caulking?
Like most maintenance work, preparation is the key to a good job. Removing the old sealant and cleaning the aged sealants from the parts is key. Preparation generally takes the most effort and time, and like painting, the application of the caulk is the last step. In many instances the seal or gasket is behind a door or window requiring removal of the object to replace the seal.
RV Delamination Repair System and Sealants