Outside caulk is used for keeping the elements (rain, water, snow, air) out, to keep insects and "critters" out, as well as for aesthetic reasons of filling gaps and cracks
Outside caulking requires both a caulk with good flexibility and colorfastness (if you are using a matching caulk and not painting over it). Caulk beads on the exterior are usually a bit bigger than interior caulking and are often tooled.
Exterior caulking can be quite extensive. It is very common to go through several cases of caulk when caulking an exterior. For this reason a caulk gun with a good thrust ratio for ease of application is important.
Backer rod
Some gaps on the exterior can be wide enough that you will need to fill the void first with what is know as “backer rod”. Backer rod is a round foam material that comes in various sizes. The purpose of backer rod is to prevent caulk waste into a bottomless void.
For new construction, where you are going to paint over the caulk, silicone modified latex caulk works well and is very paintable. Where you are not going to be painting over the caulk OSI Quad comes in a multitude of colors and retains it’s color very well.
On repaints you may need to pull out old caulk, before re-caulking. Use a 5 in 1 tool to dig out the caulk. You may find that it is tough to get all the old caulk out. Often you can caulk over it with a little wider bead.
Tooling the caulk: The spatula (the professional's caulking tool)
Good looking caulking is important. Exterior caulk beads are bigger than interior caulking making it all the more important to do a clean neat job.
The primary tool for tooling is a spatula. Spatulas are manufactured specially for this purpose. Caulking spatulas come in different sizes. Basically, they are thin 1” (approximately) wide putty knife-like tools that have rounded corners. Small beads can be smoothed with a finger or left alone if done well.
Dust out the joint with a dust brush, and apply the caulk bead into it. Once the bead is down, take your spatula and holding it on a 30 degree angle or so, smooth the caulk out. Some caulks will tool better than others. Soft low viscosity caulks won’t tool as nicely as heavier bodied material like OSI Quad.
Using a wide tip
I use a bulk gun (fully enclosed cartridge Newborn Brothers Co. model 316) for exterior caulking. The advantage of a bulk gun is two fold: it allows use of bulk caulk for larger jobs, and allow use of cartridge caulk through a gun that you can change tip size. Wide tips will span over smaller dried out caulk beads without the need to remove them.
See related articles:
CRL 8" x 1-1/4" Spatula for Joint Tooling
Xpress Seal Pro- Professional Caulking Kit for the Pro Caulk Look
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Exterior Caulking
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