best caulk for fiberglass shower surrounds

homeboundSeptember 22, 2007

Question for the pro's.

Mfr. instructions say to finish caulk a 3-piece fiberglass shower surround with acrylic latex caulk (white), but I'm leery about that long term as far as mold and mildew growth. I absolutely don't want to recaulk after a year or so.

Is acrylic latex stuff what you pro's are using, or something else? I need a white finish. (This is an "Eleganza" unit from Lowe's.) I'm considering Polyseamseal Ultra (for baths), but I haven't yet seen how well that holds up long-term.


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The caulk that is correct for using in baths/kitchens dries with a shine and has moldecides in it. That means it is difficult for mold/mildew to stick to the caulk, the caulk is just as easy to clean as the enclosure, and nothing else will stick to the caulk---ok except soap scum. :)

The correct caulk will also have Not Paintable on the container.

    Bookmark   September 23, 2007 at 8:27AM
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Brushworks Spectacular Finishes

The advantage to using an acrylic is what mac already mentioned plus, when you replace it years down the road, it's much easier to get caulking to adhere to the joint. Caulking won't adhere to any traces of silicone caulk. Silicone caulk will not even adhere to itself!

You're doing the right thing. Be sure the joint is tooled for proper adhesion and waterproofing.


    Bookmark   September 23, 2007 at 3:47PM
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Thanks guys.

BTW, what do you mean "tooled for proper adhesion and waterproofing"? I usually prep with a clean and dry joint, and apply caulk smoothly with no gaps, sometimes masking the edges first. Do you mean anything else?

Also, can anyone suggest a caulk name they like for this?

    Bookmark   September 24, 2007 at 7:52AM
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Using a caulk other than what the mfgr suggests could void any warranty. If you have a defective product and make a claim, they could use that to come back on you. Otoh, in this case it would be the install that has any real chance of failing and not the product itself, so mac's advice of acrylic with mold inhibitors would be best bet.Most acrylic latex caulks have the inhibitors when labeled kitchens/baths. Read the labels!

    Bookmark   September 24, 2007 at 11:26AM
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Yes of course! Mrf. directions just say to use "acrylic latex" without any further info.

Reading the labels today I learned that Kwik Seal is acrylic latex....with added silicone in the fine print. It's labeled "paintable". Then I called DAP about it to see if it dried glossy: "No, but Kwik Seal Plus does." This was not on the shelf.

Then I read the low-down on Polyseamseal Ultra (their "best" for baths & showers.) It's not acrylic latex, but it is high gloss. Fine print also says it has some silicone. And it is also labeled "paintable".

I suppose I'll try another store to find Kwik Seal Plus, but I'm still open to other specific recommendations.


    Bookmark   September 24, 2007 at 5:21PM
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I called the Mfr. today. Turns out that what I thought was fiberglass is actually something else - polystyrene (plastic).

They say that's the reason I can't use 100% silicone, but that I could use GE silicone II, among other things.

    Bookmark   September 25, 2007 at 9:13PM
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Personally, when I apply most caulks, I use my index finger to "tool" it. Kind of slide my finger along the bead. This tends to push the caulk into the joint, and create a better seal with the two sides of the joint. And you end up with a kind of concave beveled look to the joint, as opposed to the convex bead that you get if you just apply it and don't touch after that.

Have paper towels handy to wipe off the excess silicone caulk that will be on your index finger (*smile*).

I also like silicone caulk that's labeled for "tub and tile" (has mold/mildewicide in it) a lot better than acrylic latex, since it flexes, like GE Silicone II Kitchen and Bath (with BioSeal). Yes, when you renew it, you'll have to remove the previous caulking, but it lasts a lot longer in my experience, adheres better, flexes, stays flexible, etc.


    Bookmark   September 25, 2007 at 9:18PM
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