Silicone caulk problems with new replacement vinyl windows

Las Cruces, NM(Zone 8a)

My husband and I are replacing the 1960's aluminum windows in our brick house with new double-pane vinyl windows. We have four installed, eight more to go.

I used standard "acrylic latex plus silicone" white caulk on the window interiors, no problem. On the brick exterior the caulking is tricky because the caulk has to bridge the gap between the vinyl window and the bricks, as well as the mortar gaps between bricks. Lots of meticulous caulk tooling.

The vinyl windows are tan in color, so I chose GE Silicone II 100% Silicone Window and Door Sealant for the exterior, because it was the best color match for the tan windows. Also, I read that silicone was a good quality caulk with good adhesion. It's a bear to apply compared to good old acrylic latex, since it's not water soluble, but I've hung in there. I used foam backer rod in the gaps to provide a good foundation for the caulk.

The problem is, I noticed today that the silicone caulk on the first window we completed (about a month ago) is pulling away from the vinyl window. I don't want to complete the other windows and watch the caulk fail.

First question, has anyone else had a problem with silicone caulk not adhering well to vinyl windows? I thought this stuff was supposed to stick well to any hard surface. It's sticking to the brick and mortar, but not to the smooth surface of the vinyl window edge. Anyone know why?

Second, since I now have to rip out and replace the caulk on the first window (and maybe others) does anyone have a recommendation for a better caulk to use? It has to be something that I can find in a tan color, white will not work for our house exterior.

Our entire window replacement project is now at a standstill until we can resolve this caulk problem. Any help is greatly appreciated...winter is coming and I am getting really frustrated!
Thanks folks!

West Pottsgrove, PA(Zone 6b)

Was it hot when you used the silicone? It can shrink when it cools down. Also, it may be a question of how big a gap you're trying to fill. What kind of caulk does the window manufacturer recommend?

Las Cruces, NM(Zone 8a)

Hello claypa,
I don't think the temp is the problem, it's mostly been in the 70's-low 80's. The caulk tube says gaps more than 1/2" by 1/2" need backer rod, which I used, so in most cases the gap is closer to 1/4" by 1/4".

No mention of caulk recommendations in the window manufacturer's website/literature. The sales rep suggested an elastomeric caulk, but I couldn't find any in a color compatible with our tan window color. I actually thought pure silicone was a step up in quality from elastomeric caulks, but maybe that's wrong? I will admit I haven't used silicone caulk very often.

I appreciate your suggestion, a good next step would be to phone the manufacturer directly to see what they say. I sure don't want to have to redo all 12 windows!

Dublin, CA(Zone 9a)

I'm not a caulk expert so won't try to advise you on the right kind, but if you do find out that silicone was not the right one and you should be using something else, you might try looking online to see if the right kind is offered in the color you want and either buy it online or see if your local home center will place a special order for you. Mfg's might have a number of different colors that they make but home centers are only going to stock the most popular ones.

Las Cruces, NM(Zone 8a)

Thanks ecrane, you're right about the limited color selection available in the stores. Looks like we'll have to wait until Monday to contact the manufacturer. Too bad white windows would not work on our adobe brick exterior, it would have made things much easier! I think special ordering might be the way to go.

So.App.Mtns., United States(Zone 5b)

The BEST exterior sealant I have ever used is Tremco's acrylic monomer caulk, usually a commercial product and seldom found in DIY box stores. I had to order a full case from them but 12 tubes was barely enough for my many windows. Many colors available. I'd call their customer service for advice. They have a web page with contact numbers.

Las Cruces, NM(Zone 8a)

Thank you, darius. I haven't seen that available locally so I'll go through their website. I've been using a caulk called Big Stretch for the exterior gaps between the brick and the window frame. So far it seems to be working quite well and it's very easy to apply, and their gray color is a decent match for the brick mortar. However, we have lots of work to go on the exterior, so I'll look for the caulk you mentioned. 12 tubes wouldn't worry me either, and I'd rather use the best I can find.

Dansville, NY(Zone 6a)

I use that Big Stretch too and love the stuff .
Also your window frames could have had some oily residue on them
from handling.

Las Cruces, NM(Zone 8a)

The Big Stretch seems to be holding up great, even on big gaps. Since it's water clean up, it sure was a lot easier to tool a nice smooth bead than that pure silicone caulk was.

We think you're right about possible residue on the windows. Now I'm cleaning the vinyl before we install. It can't hurt...

Post a Reply to this Thread

Please or sign up to post.