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It seems a never ending battle with mold/mildew on my log home.  The home is about 30' tall at the peak so it's difficult to get on ladders each spring/fall and scrub the logs to clean them.  If I just spray on Log Wash, it doesn't do anything unless I scrub.

I just stained my home 2 years ago.  I pressure washed it last summer and washed it again earlier this spring.  I use Log Wash.

Does anyone have any suggestions on how to prevent this?  Or is this just the log home life and I should get used to it?  I've been dealing with this for 19 years now :)

It wouldn't be so bad if I could just spray something on the logs and the solution would take off the mold/mildew, but it seems I have to hand scrub to get any impact.  With a 3500 sq ft log home, 2 stories, that's a lot of hand scrubing ;)

I've attached some pictures.  There is both white and black mold in various places on my home.  I appreciate any feedback.


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Mr. Timothy,

 I'm no expert in this area, but my cabin's surrounded by tons of trees on three sides and we're in the Caribbean. Mine is only 24' high, but I hose down the logs after using a bleach solution or TSP. I then allow them to dry about 3 days, and have been using Woodguard for the past 27 years and it works great. My logs are borate treated.  Judging from your pics. it looks like your logs were pressure treated. If so, maybe your treatment doesn't adhere well to them. If they aren't, make sure you're not power washing them to hard, I believe you shouldn't exceed 500 psi or you'll damage the logs. look into it. Hope this helps some.



Next time you clean and apply a clear coat add mildecide to clearcoat.  That will help your maintenance troubles. Jomax is a good cleaner but you have to be careful and your existing clearcoat before you reclear has to be in good shape or it can damage the color coat. Of course always spot treat before moving forward full throttle.  


Dont pressure wash at all. Hand wash with a brush and regular water pressure. Pressure washers are nothing but trouble if not removing stain. 


Thanks for sharing the info and photos.  From the photos it doesn’t look all that bad.  You are getting the mold  because you applied an oil based finish which is a good environment to culture this type of mold.  It also appears that the home may have been coated multiple times with various finishes creating and incompatible conconglomerate conducive to mold.  You can keep fighting the situation, remove the finish and use a higher quality finish, or let it go as your 3 different options.  If it’s in the budget I suggest media blast that old finish off, sand, spray logs with borate and stain with a high quality multi coat finish.


I agree with Tom. Those oil based stain do that for sure in their older age. 

Hi Tim,

It looks like you have plenty of replies but for what it's worth, I had some very old logs on a 1940s cabin with LOTS of mold and mildew (my logs were basically black). I media blasted using crushed glass, osborn brushed the logs, applied penetreat (borate treatment) and then applied 3 coats of Sashco Transformation with a mildewcide treatment added to the stain called "Stay clean". My logs have been rock solid ever since.



From your pictures, it looks like you have a clear finish on your logs, something like Sashco's Transformation. We made the HUGE and costly mistake of having Transformation applied to our log home when it was new. We noticed mold/mildew within a year, and had it hand-scrubbed with cleaner and recoated by one of Sashco's certified applicators. A year later, same issue. Cleaned and recoated at year 4. A year later, more mildew, and a year later it was cleaned and recoated. Mold/mildew persisted. We contacted Sashco at each recoating and they failed to respond to any of our complaints! We finally had our home media blasted and recoated with WOODGUARD Stain and have had no issues of any type since! Our home is NOT in a  wooded area and has plenty of air circulation around it, and we are not in an unusually hot humid area, so those are NOT factors in our mold/mildew issue.

The thing to understand about COATINGS like Transformation is that they are by no means a "stain", they are tinted coatings and do not adequately penetrate and protect your wood. Instead, they lay on the surface of the wood (and will likely peel over time). Furthermore, independent testing of Transformation showed that it is not mildew/mold resistant like true penetrating stains. This testing was done by a major log home company several years ago. If anyone doubts that this coating does not absorb moisture, which breeds mold/mildew, try this: thoroughly spray water on the side of a Transformation coated home for several minutes. Note any area (especially the bottom edge of a log) where there are "drips" or "lexcess buildup" of the coatingn, you will see where the coating has become milky colored. This indicates that the coating has absorbed some of the water (just like a sponge), which clearly means that the coating is HYGROSCOPIC. By absorbing water, you are predisposing your home to mold and mildew, teh whole time thinking that you were protecting it!

We strongly urge our clients to use WOODGUARD or CTA OUTLAST Q8 LOG OIL when staining their homes, each of which has been time tested and proven to resist mildew and mold, and have thousands of satisfied users all over the nation over the decades.

Man I’ve seen some bad information here but you top the list of not having the slightest clue what you are talking about.

Colorado Log Home Finishing:

I do not believe in bashing other responders as you have done with me. But I will question your "worldliness". TRANSFORMATION may work in Colorado, but it is a proven fact it does NOT work in PA, NY, OH, etc. We know from feedback from many, many log home owners and their experiences are directly supported by independent testing. I am not sure what part of independent testing you do not understand, but it is what it is...cold, hard factual scientific data by an INDEPENDENT testing lab (not some guy with a bucket of coating and some logs). I can also refer you to several log home finishers throughout this area who also have had terrible experience with TRANSFORMATION over many, many years. Plus, I am responding to you without calling you "clueless", but I can say you are not well informed or experienced about these coatings and their dismal performance in the lab and in the real world of THIS area! So, please, understand that scientific data under controlled conditions is fact and that is supported by field data, so the conclusions I have made is that TRANSFORMATION is merely a coating and is not conducive for use in the environmental conditions prevalent to our area. Now, unless you have lab data and field data from our area that refutes this, let us accept that you may be right for your area and that we are right for our area!?

Also, Sashco did NOT support their TRANSFORMATION product and respond to our many complaints in writing....which, again, you would know nothing about!


Thank you for sharing your experience as I very much respect and value your opinion regarding Sashco Transformation and I am not doubting what you are saying in the least, BUT I do think that there are thousands of happy Sashco customers out there (me being one of them) who have not experienced any of the issues that you have so I think it's fair to say that your experience doesn't represent the majority in any way.

One thing that I ALWAYS make sure that I tell people when I refer Sashco (as I did in the above message as well) was that it is VERY important to use a mildewcide with this product. My logs were black with mold and mildew when I bought the cabin in 2012 and I am now heading into my 4th year without any signs of issues and we are located in the far Northeast corner of the US where there is still 4ft of snow in mid-April.

I will let the pictures speak for themselves as Sashco (when used and applied correctly) is an excellent choice.  

Original 1940 log cabinCompleted Cabin

Nicholas, MOLD BUSTER was used each time the home was coated with TRANSFORMATION and we did use one of their certified applicators. The environment in PA/NY/OH is very conducive to mold/mildew and every home we have seen TRANSFORMATION applied to, it is an issue. In fact, Sashco even changed their warranty on TRANSFORMATION a few years after our initial coating was applied. The independent testing showed that TRANSFORMATION does absorb moisture (water) and supports mold/mildew growth, so our belief is why even bother with it, why not use a truly proven product for the area. On a positive side, I do like the Sashco CONCEAL caulking and recommend it all the time as it is a great performer.


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