Caulking Tip

I usually do not get along well with a caulking gun and was talking with a friend who did caulking with the Bricklayers union. He told be that his crew did a job that used 20,000 pounds of caulking. He used Dow Corning silicone caulking. The manufacturers recommend that a bead of caulking should be half as thick in the center as at the edges. This allows for stretching / flexibility in the center and good adhesion in the center. Surprised me but now seems reasonable.

It sure would look nasty like that.

Dow Corning Reccomendation

Never knew that. If you use the round foam backer rod in the joints, it gives that effect.

Another tip..use a battery powered gun! Milwaukee makes a great one and can get a sausage stuffer kit for it!

I've been around and done quite a bit of sealant work with Dow products like 795 and others. It's a quality product with a good warranty.

There is a sealant joint design for this and all sealants like it. If the design is deviated from you may either exceed the limitations of the product and or it may not perform as intended. See page 57 of the attached technical manual. This technical manual covers this material in depth. Most would not realize the details involved in the correct use of this material.

From Page 57:

"A properly designed moving joint with a 2:1 width to depth ratio will accommodate more
movement than a thick joint (i.e., 1.5:1 or 1:1 ratio). Sealants are designed to deliver optimum performance when the joints are shaped like an hourglass and use the 2:1 ratio."

We would often build a mock-up of a given assembly or exterior building component that has a sealant joint to prevent air and water infiltration. The manufacturers representative or testing company would cut the sealant joint so as to be able to pull test the material to insure it has achieved an acceptable bond to the substrate it is applied to. All substrates must be verified to be suitable for a particular type of sealant, which also includes substrate preparation, such as cleaning and or priming.
Dow Corning Tech Manual