Mildew on Soffits...Need Recoating Advice

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Old 08-19-13, 10:17 AM
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Mildew on Soffits...Need Recoating Advice

Hi Folks,

Our house has mildew on almost all of the roof soffits. The underside is the worst, but it's also on the facia. I'll get some pictures to show soon.

The soffits are all wood...1x8 for the facia boards, and 1/2" plywood on the undersides. Both have multiple coats of white stain. Cabot and PPG oil based stains I think (I'll confirm with pics of the cans). Both stains get mildew, and both at about the same rate.

I'm planning to recoat all the soffits this fall. Would like to use a product that is better for mildew...

Should I switch to paint? We used stain initially thinking it wouldn't peel (and it hasn't). But other than that detail, I'd be happy to switch to a paint if the mildew resistance is better (the grain of the wood is already fully covered with multiple layers of stain).

Is there a good mildew resistant stain? We switched to PPG because Consumer Reports rated it better for mildew. However, I'd say it was no better than Cabot. Is water-based stain better for mildew (we used oil based thinking it would last longer)?

Any other ideas for eliminating soffit mildew?

Thanks!
 
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Old 08-19-13, 01:59 PM
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First order of business is to remove the mildew.Easiest way to do that is to mix up a bleach/water solution [40-50% bleach] and spray it on with a pump up garden sprayer, let it set but not dry and the rinse it off with either a garden hose or pressure washer.

Latex coatings are a little more mildew resistant. If you want to switch to latex stain - add TSP to your cleaning mix. Extra mildewcide can be added to either oil base or latex and I highly recommend doing so! Paint might preform a little better, not sure it's worth the extra effort.
 
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Old 08-20-13, 09:03 AM
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Zinsser Perma-White?

Thanks Marksr!

I've had good luck cleaning the mildew with the method you describe. I've also used SoftScrub and added more bleach to it...that works great for scrubbing because its thicker so it hangs on the down-facing surface, and it has a mild abrasive that rinses right off. I do a double rinse....first with TSP then straight water. Unfortunately I've had lots of experience cleaning it off!

Does anyone have thoughts in Zinsser Perma-White Exterior as a mildew resistant paint? I always think of BIN when I think of mildew, and this may be a good option for my situation.

https://www.rustoleum.com/CBGProduct.asp?pid=327

Here's the overview from the site:

OVERVIEW:
PERMA-WHITE® Mold & Mildew-Proof™* Exterior Paint is a premium quality exterior paint that’s guaranteed to prevent the growth of mold & mildew on the painted surface for 5 years and to resist cracking, fading, peeling and blistering for 15 years. A great choice for any home where the growth of mold & mildew is a concern, the durable formula is tintable to a variety of popular, decorator colors. Available in Satin and Semi-Gloss sheens.
PRODUCT FEATURES:
Mold & Mildew-Proof™* paint film - guaranteed for 5 years
Durable, long lasting finish - guaranteed for 15 years
Self-Priming - sticks to surfaces without sanding
Fade resistant
Resists dirt and moisture
Tintable to any off-white, pastel or medium earthtone color

*This product contains a mildewcide to prevent the growth of mold and mildew on the paint film only.
 
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Old 08-20-13, 01:59 PM
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I didn't know Zinnser had an exterior version of PermaWhite. Their interior version is a great coating for mildew prone applications! Having never used it I can't say how well it preforms but I wouldn't be scared to try it. Zinnser has quality primers and the interior PermaWhite is good, hopefully the quality continues with the exterior paint.

I always think of BIN when I think of mildew
can you explain that statement? While BIN is an excellent stain hiding primer and has great adhesion properties - no primer or paint should be applied over mildew.
 
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Old 08-21-13, 06:20 AM
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Primer for Perma-White over Oil-Based Stain?

Thanks Marksr.

I should not have associated BIN with Mildew...I meant to say that I think of BIN as a great coating to cover up stained or discolored wood. We used lots of it when these facia and soffits were new...mostly to cover up knots in the pine and plywood. Its worked great over the years for that. Have not tried using it to cover mildew stains...but after reading up on the topic, I suspect it wouldn't be great for that.

Yes, I'm finding mostly positive feedback on the Zinsser Perma-White Exterior. Since no other coating claims to be designed for high mildew areas, I'm inclined to give it a try. Of course there are plenty of paints that can have additional mildewcide added. But this is the only exterior product that appears to have been designed for this purpose. So I'm going with the experts instead of trying to whip up my own formulation...

Price is $33/gallon, so not out of line with other paints. Only issue is finding it...nobody stocks it around here, which is surprising because I see mildew on houses all over the place.

Do I need a primer to put this paint on top of an oil-based stain? It says self priming...not sure if that applies to previous oil-based coatings.
 
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Old 08-21-13, 07:19 AM
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No Primer...According to Zinsser

I called Rustoleum Zinsser, and they recommended no primer for Perma-While applied over oil-based stain. So instead of priming, I'll probably shoot for 3 coats of the Perma-White.

I'm renting a tow-behind boom for a week for this job...so that should help with all the surface prep and multiple coats. Hoping to ignore it for 10 years after that...
 
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Old 08-21-13, 07:58 AM
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JoMax for Prep?

One more question on my mildew situation...this time surface prep.

I've seen quite a few posts that refer to JoMax as a cleaner prior to painting.

For my case, seems like the JOMAX® House Cleaner and Mildew Killer would be the right product:
Zinsser JOMAX® House Cleaner and Mildew Killer Product Page

Is there any advantage using JoMax instead of just a strong bleach solution?

In the past, I've prep'ed with about 1/4 to 1/3 bleach in water and scrubbed with a stiff brush. I've also used Soft Scrub with bleach and added a lot more bleach to it, which is helpful to keep it hanging on the surface for the 10 min soak period. But I've always had mildew come back.

Does JoMax add any special sauce that would help kill off the mildew beyond the bleach?

Thanks!
 
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Old 08-21-13, 12:37 PM
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I think JoMax uses an oxalic bleach instead of normal bleach which makes it more diy friendly [less likely to harm vegetation] IMO there is no real advantage to using commercially prepared cleaners when bleach/water solution works just as well for less money.

I agree there shouldn't be any need for primer over the existing stain .... unless there are areas of raw wood. If you can't find the exterior PermaWhite, I wouldn't be leery of adding extra mildewcide to any quality stain or paint.
 
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Old 08-21-13, 01:49 PM
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Thanks Marksr...Great information as always. In searching forums, I see that you've been at this for a while...saw posts from you back in 2007. Keep up the great work...lots of help to lots of people.

I got the same impression about JoMax from reading forums...its the bleach that does the killing, and the rest of the chemicals are window dressing. I didn't know about the bleach type difference...but that makes sense. The vegetation is not a big issue for my project.

I'll pick up a gallon and do a side-by-side run off between clorox+water and the JoMax formulation...will report back the results but I tend to agree that there's probably not a big difference.

Regarding Perma-White availability, I was able to order what I need from a local paint store, so should be all set. If anyone else is interested in this paint, it can be ordered online with free shipping from Home Depot (I like to give the local guys business when I can so didn't order from HD).

Thanks again...with your help, I'm now confident in my plan.
 
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