To calk or not to calk......THAT is the question

[brianwelch]

Thanks for all the responses guys.  I'm not going to CAULK the horizontal edges, but everything else, and not worry about the paint issue.

Like so many other items, the key to a successful project is preparation. Trying to prep the horizontal joints properly would be not only nearly impossible, but extremely expensive/time consuming, with little payback in the long run. Caulking the ends and at dissimilar materials is both critical and effective.

[Bibliophile 13]

Sounds like a good plan.

I have similar siding on my house. No idea how old it is, but the house itself is 100 this year. At some point, somebody did caulk a lot of the horizontal joints. We're in the middle of repainting, and we're leaving the tight seams uncaulked. But there are places where the wood has warped over time, opening up a small gap. Those gaps are getting caulk. With care, the caulked spots will be invisible because I'm shooting the caulk up into the seam. Oddly enough, the vertical seams have not been caulked. I'll probably do those as we come to them.

I don't buy the whole "let the house breathe" thing. Old houses breathe plenty on their own. The typical problem is that they breathe too much, which makes heating and cooling inefficient (read: expensive). You're not at risk of making an old house a hermetically sealed container. So if you can see a gap, do what you can to close it up. Multiple little fixes go a long way.

[daddo]

I say the wood lasted 140 years without caulking under there. The question is; Is that one reason why?

[hbmcc]

By standard building codes homes didn't need a vapor seal until after the 1980's. Even with my bevel siding being un-caulked at its contact with deck boards for nearly 40 years (built 1985) wet conditions didn't move more than about 3/4 inches, as shown by stains and chlorine bleach. 

We live in a West-Coast Mediterranean Climate so summers are up to four months of 0-precipitation and winters--the other eight months--are wet constantly, even with 30 inches of annual precipitation. I only wish new residents always moved here in the fall, just about when the rainy season starts.... The Lewis and Clark expedition hated the winter they spent near the Pacific Coast.

Big gaps in siding attract bugs and larger critters. My bevel siding has over an inch overlap which is significantly more than the OP's siding. I also have roof overhangs exceeding 24 inches, that shield the siding from most rain. One's mileage can vary in any condition, so getting many recommendations from known experienced sources in your location is the only legitimate means. Also, history is the best teacher. Don't just rely on "He Said...".

[FireWood]

I'm a little late to this, but the rules I was taught on on caulk are pretty simple.

1) Caulk everywhere that water can get in.

2) DON'T caulk anywhere that water can get out.

3) Remember that it's a building and not a boat.