Why Latex Caulk?

[Dennis McDonaugh]

My house has a "skirt" of bricks about three feet tall that goes all the way around house. There's a 1X2 cedar strip on top of the bricks and a galvanized drip cap on top of the cedar strip. The top of the cap slips under the siding. The gap between the top of the bricks and bottom of the cedar strip is caulked with Latex caulk. After only three years its coming loose and needs to be redone. I'm thinking silicone caulk would be more durable, but I wonder why the builder used latex and if there are any down-sides to using silicone caulk.

[Kevin Gerstenecker]

Dennis, the builder probably used latex because it is inexpensive, and perhaps he was using this latex for another application, and used whatever he had on hand. The only thing I can see where Silicone would not have been better would be if it was to be painted. Paint and Silicone don't get along. They are making a Siliconized Latex Caulk that will take paint, but IMO, it is not nearly as good as straight Silicone. One better would be a caulk we use commercially, the trade name is Vulkem. Comes in a gun grade and self leveling, and it is the best sealant I have seen. Long lasting, and durable, and makes a very watertight seal. We use it in area where the concrete meets the structure, and for walkway expansion joints. A little costly, but worth the extra money in effectiveness and durability.

[Chris Padilla]

Go for a polyurethane caulk instead. I think it is more durable. At least grab a tube and read up on it.

[James Carmichael]

Dennis,

I feel your pain. I replaced a ton of rotted cedar trim on my last house. Rather tricky since the builder used 7/8" stock, had to search all over town to find it.

After caulking, I had a major project deadline to hit at work and it was several months of 70-hour weeks plus the carpenter ant interlude before I could get around to priming and painting. Anyway, the DAP latex caulk had already shrunken and was showing gaps. Not knowing any better at the time, I went back to HD and bought DAP DYNAFLEX 230, which is also a latex caulk which I think cost about 2x as much as DAP's next highest grade, but the difference between the two was night and day.

Could be the stuff Kevin and Chris are recommending are better, but the DYNAFLEX 230 was sure worth the extra money for me.

[Jerry Olexa]

Latex caulks are good inexpensive, short term solutions. Silicones are more expensive but higher quality, more durable and longer lasting (but not paintable).I'm not familiar w the Poly Caulk Chris mentioned. Generally I use Silicone for exterior.

[Jason Roehl]

I've run MILES of caulk. I've probably regrown my index finger several times over due to caulking and wearing it down smoothing out the caulk. When it comes to latex caulks, there are many, many grades of it. In general, they sift out like this:

Latex caulk: ok for interior cosmetics, not so good for exterior where more movement occurs. Cheap.

Acrylic latex caulk: pretty good for interior cosmetics with some movement, ok for exterior use, but not great. Still pretty cheap.

Siliconized acrylic latex caulk: IMHO, not so good for interior cosmetics (not as easy to tool/smooth QUICKLY), excellent for exterior use where there is movement, but the joints are not too big, maybe up to 1/4". A little more than cheap.

All of these are paintable, though I have run into some brands of siliconized ALC that didn't take paint all that well, even though they were labeled "paintable."

I do like the apparent durability, longevity, and levelling of the polyurethane caulks, and they're not too bad to tool (a little sticky and messy, though), but they are a little more pricey, and take longer to set up and be paintable (some ALC's are paintable in less than 30 min). BUT, if I have a big gap to fill, I like poly.

All that being said, if I had a gap to caulk that was not to be painted ever (like a brick expansion joint, or a sidewalk, or glass to vinyl, etc.), I would grab the silicone caulk. I have to put that in there because my dad worked his entire career at Dow Corning (#1 world producer of raw silicon products). I have argued with him on it's applicablity in certain exterior situations where paintability is a concern, such as wood moulding next to brick (don't use silicone there...).

Aside from that, there are many, many more types at varying dollar amounts. I can get the latex caulk for about $.75/tube, and I have used log home sealants that ran up to about $10/tube.

On edit: As for the situation of the brick-to-cedar gap, I would use either the siliconized acrylic latex, or the polyurethane, depending on the gap size. More than 1/4" (average), and I would definitely go poly. Either way, I would stay paintable. Cedar does not last forever outside, so at some point it will need to be stained or painted, and the caulk will need to be tooled onto the cedar. You don't want just a round bead, as that leaves very little contact area on either substrate, and it will pull away quickly once it shrinks (they all shrink to some degree). I suspect the builder used a cheap caulk and didn't tool it.

Addy protocol: experienced professional painter

[Dennis McDonaugh]

Thanks for the info guys, there's a lot more to caulk than I thought. I'll take a look at the poly caulk--I don't want to do this again soon.

[James Carmichael]

One last (OK maybe more than 1) thought Dennis: Remember, caulk is intended to cover, not fill, a gap. I've done the brick-to-cedar sealing. Prior to caulking, close the gaps as much as possible. I found it necessary to replace a lot of the cedar and close the gaps with nails or screws. I found lots of rotted wood on the underside where water had seeped into gaps and having little exposure to air, did not evaporate. If you end up replacing any, it may be a good idea to seal both sides with stain or paint before attaching.

[Jason Roehl]

James is right. Filling a void with caulk will make the caulk too stiff and hard to stretch for the movement. In other words, the force required to de-adhere the caulk is less than the force required to stretch the caulk when movement occurs. That's why I made the '1/4" recommendation.' For an ALC to work in greater than a 1/4" gap, there would need to be a "bond breaker" behind the caulk, such as closed-cell foam rope (weatherstripping). That will fill the gap, and the caulk will ride on top of it without bonding to it, allowing the gap to be bridged by an hourglass-shaped cross-section of caulk, with the thickest parts being the areas where the caulk is bonded to the substrate (the brick and the cedar in your case). Then, the thinnest part of the caulk in the middle is the part that is easily stretched/compressed to allow for movement. This is the absolutely best way to do this. However, my experience has been that you can just fill small joints (<1/4") with quality ALC caulk and not have a problem.

Jason

[Dennis McDonaugh]

The bricks are tilted down a little on the outside so water runs off. They have a flat surface which mates well with the cedar except on the brick joints. I'd say most of the gaps are less than 1/16 of an inch. The original caulk was just a thin round bead which has since shrunk.