The scratch/brown and color coat do not keep moisture from getting to the wall, that is why proper install of the flashing/underlayment/ drainage plane is key to a suucesful stucco job. Caulking is extra insurance behind the nailing fins but is not necessary when the windows are flashed properly. I would question the flashing install and have them double checked before the scratch/brown coats are applied.

Mechanical flashing (proper layering) is always the first choice in proper flashing. Chemical (adhesives, caulks, etc.) should only be used as "backup" as appropriate; not the primary flashing method. That being said, what does the window manufacturers install instructions state? If it requires a bead of caulk on the fin, I'd make the builder re-do every window. If it does not, then the risk/cost to change them is up to you to determine. My advice would be to caulk them though...

I agree with buzzsaw. Mechanical flashing (properly installed) is priority one. We always caulk our fins unless the manufacturer were to specify otherwise, though the caulking is mainly for air infiltration. I've never run into a manufacturer who did NOT specify caulking but I'm sure there must be some? The only downside to caulking is it can be messy and add time to the install but that's hardly an excuse to leave it out.
Unless the GC screwed the fins, removing the windows to add caulk will be a real joy and perhaps encourage him to follow all the steps in the future?

fwiw, i always caulk behind the fins as well as stated: "it's extra insurance".

Even at that, the flashing should be checked on the op's project because of the seeping after a driving rain.

Andersen does still recommend putting sealant behind the nail-fin of a series 400 Tilt-Wash Double-Hung window but it serves little purpose since their method of attaching the fin to the window frame on this model is not water tight, especially at the corners (the casement and awning model fins are integral with the cladding). Also, this sealant can often get squeezed out when the fin is nailed and can lead to poor adhesion of the self-adhering flashing so it should be applied in a small bead close to the opening.

Andersen now recommends that sealant be applied to the fin-to-frame joint at the edge of the flashing tape after the window has been flashed. What Andersen shows at the sill appears to be DuPont FlexWrap and I would assume StraightFlash is used at the jambs and head since these are self-adhering butyl flashing products that are more compatible with typical window sealants than some bitumen-based products.

This fin seal detail and the addition of a sill back-dam and sill flashing wrapping up the jambs represent a major improvement in waterproofing for Andersen double-hung windows. I would pay more attention to these details rather than worrying about sealant behind the fin.

What Andersen omits is the necessity of rolling the flashing tape with a small steel-wheeled roller in order to insure adequate adhesion.

Hi mightyanvil, good to see you back! A lot of folks here missing your expertise. Welcome back!

Ditto to what sierraeast stated MA! Very (happily) suprised to see you post. Here's to having those trolling jerks stay away and have the good (informative) people stay on!

There is no way I would have the builder reinstall the windows, especially since they are already flashed. The Andersen 400s I've seen have an integral vinyl flange to the cladding. To tear off the flashing and pry up the flange would leave a mangled mess, and probably leave you worse off than before. The merits of the caulking are debateable with proper flashing. I would sleep just fine at night knowing the windows are flashed properly.

As I live and breathe....welcome back, MA!

Amy

I hope you are able to solve the water problem whistelpigger!:)

Hmm...glad to have one poster gone and one resurrected!

Thanks for the kind words. On the 400 casement/awning the fin is integral with the frame cladding. On the 400 double-hung (Woodwright or Tilt-Wash) thin fins slide into grooves on the sides of the clad frame and overlap at the corners. It would be helpful to know what type of window is being used.

Nice to see you mighty!

As Sierra said you should have a water tight house at this time. Stucco is not your water barrier, if you are having seepage now than something is wrong. If you could post pic of your install than I am sure that we could find the problem.

If you flash your windows over the fin and over the nails used to hang the window, no problem. If you flash and leave the nails visible you’ll have problems.

Hopefully they have not had an issue in the 13 years since they posted their question.