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Problems With Mildew on the Exterior of my House

3K views 23 replies 8 participants last post by  spraygunn 
#1 ·
My house is only 2.5 years old, and I have bee having trouble with mildew before we even moved in. The fascia and freeze boards are 1x4 Hardie material. Each of those have 1x2 pre-primed tongue and groove wood strips at the top. The painter claims to have put an additional coat of primer plus two topcoats on all exterior trim, yet, within 4 months, the 1x2 wood pieces started to mildew. I sprayed everything with a bleach/mildew killer/water mixture, and it all looked nice and pretty for a while. I even painted a couple test areas with some mildew resistant paint. Over the winter, it started back again. The test areas aren't as bad, but still don't seem to be the answer.

What should I do? It's quite an eyesore.

Do I need to use a good exterior paint plus a heavy dose of a separate mildew resistant additive?

Do I need to just remove all the pieces and replace with a different product?
 
#2 ·
What sheen paint are you using?
The higher the gloss the less the mold has to cling to.
Over hanging trees or shrubs up againt the house?
Cut them back.
 
#4 ·
My house is only 2.5 years old, and I have bee having trouble with mildew before we even moved in.
One possibility is that the mildew spores were on the surface before your place was painted (this might not have been evident to the painter). if this is the case, then the mildew is actually coming up from below the paint film, rather than growing on top of it.

You will have to determine whether or not this is the case before you can move on to a solution.
 
#5 ·
If the spores were painted over, does this mean they are junk and need to be replaced?

How do I determine that? It definitely looks like it's bleeding through, as the mildew growth takes the shape of the wood grain beneath. The boards consist of many finger jointed pieces, and you can see a change in severity from one piece to the next.
 
#7 ·
Finger joint shouldn't be used exterior. If the mildew was painted over and is coming up through the finish, and it can, you would not be able to get rid of it. After cleaning the finish will still have a blackened haze. You can only kill the mildew on the surface, not what is encapsulated, growing, in the paint. I see this from time to time power washing, mildew that you can't remove. If the finish looks perfect after washing, that's not your problem. Do any of your neighbors have a serious mildew problem on their house or roof? Do you live down/up wind from them? They could be infecting you. It propagates by ejecting spores that get carried in the breeze to their new home, or yours.
 
#9 ·
Mildew is very persistent. If you have any sort of shade combined with dampness, mildew is gonna grow. Blame should not always fall on the painter. Hopefully, he cleaned it in a professional manner and did not just paint over it. Make sure you trim back any tree limbs or bushes to allow air to flow and maybe even a little sunlight to hit your house where this mildew is. I live in the Midwest and some sides of houses never see any sun except in the summer months and those are the sides where mildew thrives.
 
#13 ·
It was Porter brand satin mildew resistant latex. What makes me suspicious is that the painters never left behind any empty paint buckets, not even in my readily available garbage bins. So, I didn't know if they used 10 gallons or 2. On the last day, they left one pail without about a quart in it.

Concerning the grain, it's not pronounced. It's a smooth, slick finish. You can just see the grain bleeding though. I'm going to posts pics.
 
#17 ·
The quality isn't great, but it represents the problem. It's like this wherever they used the wood 1x2, which was quite extensive.

Like I said, I can clean it all off, and it looks nice and perfect for a few months.

I live in Mississippi. It's very humid, but it's not like this is a widespread issue down here.
 
#18 ·
Every time I have ran across a mildew issue it's due to shading from trees being too close to the house. If you don't correct the shading issue the mold will just keep coming back.
 
#20 · (Edited)
To my eye it looks like some type of sap-stain type fungus, which could be present, but not visible, in the sap grain of the wood before priming. This can be exacerbated by excessive moisture in the wood when it was shop-primed by the manufacturer. That would be one explanation for the abrupt difference of discoloration on some of those pieces, finger-jointed material being manufactured from different pieces of wood. Or, it could be from mold spores present in parts of the grain structure.

If the stock came pre-primed from the yard (which is normal with finger-jointed pine) then it wouldn't be visible to your painter. High moisture and humidity can exacerbate it, and moisture can build up under that porch, although it might not be visible to you.

I'm guessing at this based on my experience with finger-joint pine 2x4 re-sawn trim, which is becoming quite prevalent on tract housing out here in the west. Stuff I saw stored over a winter on an inside garage slab, with no good ventilation, developed similar patterns through the manufacturer-applied primer.

This is only a guess. Others may come to a different conclusion. Hopefully, you will get the answer you need, and a solution can be suggested.
 
#21 ·
If the paint was the problem, all the surfaces would be growing.
If the environment was the problem, all the surfaces would be growing.
As clam has said, it's the wood, and it does look like it's growing through the finish.
Replace the trim or keep cleaning it. It's not uncommon for pre-primed wood to have a mildew issue.
 
#22 ·
Look at your second picture, the closer-up of the two. Notice where your painter did his caulking between the 1x2 and the soffit material:

From the photo, it doesn't look like there is any discoloration on the paint over that caulking bead; in fact, it makes a distinctly white line separation along the edge of the 1x2 where it meets the soffit. This is especially evident on the underside of the joint where the two 1x2's meet at the perpendicular.

This is further indication to me that the problem is below your paint films, as the thickness of the caulking is retarding the appearance of the stain/mold. It would also explain why it has not reappeared as badly on the places you washed and re-primed/re-painted: it has an extra layer of paint to work its way through there.

As JSheridan said, if it were either the paint or the environment, which would locate the problem on the surface, I would expect that caulking line to be dark also (because it has been painted over) especially when the area immediately around it is dark.

You can choose to keep washing it; however, repeated washings with bleach will eventually degrade the paint film, including on those areas not turning dark (like that soffit) if you keep hitting it with bleach.

I don't know what contract law is in Mississippi; you may have recourse against the wood supplier/manufacturer because your place is less than three years old. In California, where I am, "Homeowners must file claims for the failure of paints or stains within five years of the close of escrow."

This might qualify as a paint failure against the manufacturer, but you would have to check it out with someone familiar with contract law in your neck-of-the-woods. I'm not certain it qualifies as strictly a paint failure (yet).
 
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