Outside mildew soutions?

[Larry Edgerton]

There is this house that I built years ago that has poor moisture conditions, north side of the lake tucked up to the bottom of a high bluff so it gets very wind, surrounded by wetlands and actually has a small stream running under the middle of it. Its very tall, 180 ft. long and has celestory windows between the roof pitches that can only be serviced from an 8/12 pitch roof. Also each eave side has a 5' overhang with wing walls every 20' or so that further stop the breezes. and just a curiosity, nothing to do with the problem it has 102 windows and 33 exterior doors. Every two to three years I have to clean the black mold off of the rough cedar siding in place that are shaded or get no breeze. I

So....... What I am wondering is if any of you know of a product that PREVENTS or slows down the buildup of mildew that I could apply after cleaning and so stretch out the time between cleanings. I have tried a lot of the crap on the market and most of it is VooDoo, or really, just a scam. If you know of a product that works please tell me. Don't just google mildew and tell me what is available, I am looking for actually products that you have used and performed favorably. This place is huge so spray capability would be a huge plus. The moisture conditions here where I live with all of the water we are surrounded with can be trying!

Thanks, Larry

[Steve Hubbard]

When we had a place on a lake in Alabama, we used Jomax for mold removal, primarily on the north side of structures. Not sure it is a preventative, but when the instructions are followed, it certainly makes removal easy.

[Tom M King]

I don't have a definite answer for you, but having fought the same fight on our place, the locals call it the Ponderosa, which is on the lee side of the prevailing winds on a fairly large body of water, for 40 years, I'll have a long rambling reply later. I've found some things that help, and one fairly new thing, or at least to me, a couple of years old with good results on another place. House full of company tonight, so I'll try to get back to it tomorrow.

[Tom M King]

Sorry, been too busy to spend much time on the internet. I'll try to shorten my answer.

After decades of trying different things on our White Oak siding, on our house, barn, and other buildings here, these are a few things I've figured out.
Don't use bleach to start with, it can corrode galvanized fasteners, and leave streaks. It doesn't seem to effect stainless fasteners. Other than that, the use of a bleach soak before pressure washing doesn't seem to make much difference. Ever since the first time I now only pressure wash with water.

Pressure washer is 13hp Mi-T-M that is 4.4gpm at 2,500 psi. On the Oak we use a 25 degree nozzle, and anything else gets a 40 degree. Rental units I tried before I bought one were more pressure than that, and too much for wood. It's not possible to be but so careful when running one for half a day at the time.
Even mine is a little strong to hold up a 24' extension wand very long with. Ideally, I'd like to have one that doesn't have so much pressure back against you for the long wands. I would still want the 2,500 psi, but something less than 3 gpm would probably be a lot more manageable. We manage by taking turns, but it will still wear anyone out.

For what to leave on, I have started leaving bleach on our Oak. Pulled in with the injection setup on the pressure washer, I just give it all a quick going over, and leave it. It does take Way longer, in years, for the Oak to start to turn black.

The other leave-on we are in trials on, as suggested by expert professors at N.C. State, on another house that is painted, and in a similar wet site to yours, as well as being close to a railroad track that diesel engines leave a lot of particulate in the air, is Borax. Just laundry additive boxes of it dissolved in water. You have to heat the water to get it to dissolve good enough to stay in suspension while pumping it through a pump sprayer. This house is painted white, and so far, I've been amazed at how clean it has stayed for two years now. That's the wettest, and nastiest site I've ever worked on. I should have left a test spot bare, but the Professor couple I was working for wanted us to do the whole thing, so we did.

[Larry Edgerton]

Will try the Borax Tom, thanks.

[Tom M King]

You don't have to spray it on hot, but if we mixed it cold, enough would fall out of solution to clog the tip in a 2 gallon pump sprayer several times before the sprayer could be emptied. I heated the water in a pot I use for making Boracare, over an outside cooker burner. It doesn't have to be boiling. Mixed like that, it would all spray easily.

[Jason Roehl]

Raw cedar, or does it have some sort of finish?