brianbh

I need to do some exterior priming of stuccoboard, and I want to make sure I choose the best primer I can. Chalking and mildew are the problems.

Should I use Bullseye 123 or Kilz?

Thepaintman

Here on the west coast we have used Zinsser1-2-3 with good success. However, it will be necessary to deal with the issues of mildew and chaulking.

We use a mixture of 3 parts water and 1 part of household bleach to kill the mildew then we pressure wash to remove the mixture and chaulking. Hope this has been helpful.

chrisn

Bullseye 123, Without question

slickshift

Kilz is not a good primer
Original Kilz (oil) is a decent stain blocker
That's it, and that's all it should be used for
Spot priming stains

End Grain

If stain-killing is NOT required, Glidden's Gripper Primer is pretty good. I've found it to be an excellent prime coat on woodwork and metal doors and trim, underneath latex semi-gloss enamels in particular.

__________________
Don't force it. Use a bigger hammer.

joewho

In your situation, finding out which is better probably isn't the best way to approach this particular job.

Exterior stucco has it's own set of properties you can approach with success if you know what to look for. Natural stucco doesn't necessarily even need to be primed unless you ARE wanting to block stains. Bonding primers simply aren't necessary on stucco. The nature of the material will allow paint to bond properly. The issue is the same for paint or primer and that is to get it cleaned free of chaulk, and loose material and mold/mildew. PH balance is a factor, but only on new stucco. Spot priming dark stains, with a stain blocker is all that's necessary. Top coat with water based paint that has mildewcides.

Priming the whole project certainly won't hurt it, but it simply isn't necessary. Keep in mind that most solvent based products are perfect for breeding mold. So, make sure you cover all solvent's completley with waterbased paint.

If you want a long lasting job, use the money you would have spent on primer and get a top of the line paint, like duration, which is self priming. Stucco is NOT a material that you want to be airtight. Latex products will breath just fine. If you go overboard with a solvent based primer, you run the risk of sealing up all the pores and that will cause problems from the inside out.