Replies

1. 
   DanH | May 23, 2018 03:56pm | #1

   Cabot studiously avoids saying whether that stain is water or oil.  Which is is?

   You don't necesssarily need to get down to bare wood.

1. 
   745sarachal | May 25, 2018 11:31am | #3

   mold/mildew on red cedar shingle siding exterior

   Thank you DanH.  The Cabot product used was oil based.  Clean up was with mineral spirits.  When you say that it's not necessary to get down to bare wood - most products I've looked at require that all prior product be removed for the new product to adhere properly.  Any suggestions?  Do you have much experience with cedar shingle siding?  If yes, what products do you use?  We live in CA so VOC can be an issue.  Thank you.

1. 
   DanH | May 25, 2018 12:33pm | #5

   Completely removing the old finish is only necessary if either the old or new coat is a paint rather than a stain.  Of course some products claim to be one and are really the other, so it's a touchy topic.

2. 
   florida | May 24, 2018 07:15am | #2

    Because cedar shingles are rough and porus it makes a fertile breeding ground for  mold and mildew which will grow anywhere moisture is present. Try Oxyclean to get the mold off then figure on washing it every year to keep it looking n

1. 
   745sarachal | May 25, 2018 11:34am | #4

   mold/mildew on cedar shingles siding

   Hi Florida.  Thank you for the info.  We have been told that we have to get back to bare wood in order to put a new product on our shingles.  We live in CA so VOC is an issue.  The Cabot product we used was oil based.  Would a water based product be a better idea to keep the mold/mildew at bay?  I tried Oxyclean but it didn't remove the old Cabot Stain.  Thank you.

1. 
   florida | May 28, 2018 12:32pm | #9

   Oxyclean won't remove your stain but will remove and kill the mildew on your house. Trust me, you do not have lichen, you have mildew. I've never heard of having to remove to bare wood and I wouldn't do son on my own house. Since you can't use oil your only choice is acrylic. A pressure cleaner, used very carefully with the grain will remove most of the stain but start slow if you go that route.  

1. 
   745sarachal | May 29, 2018 12:04pm | #11

   Acrylic - any brand you recommend?

   Thank you.  I presume you looked at the photos of our house.

   Are you saying that we "can't use oil" because we will have the same problem down the road?  When you say "acrylic", is there a product that you recommend?  Is there a water based, semi-transparent "stain" that will allow some of the wood characteristics to show through?  Is Benjamin Moore Arborcoat any good for this job?

   My husband says that we have to remove the stain to remove all the mold because in areas that we cleaned with a "stripper", there are spotty remains of grayish discoloration.  We presume that any residual mold in the wood must be killed before we put any new product on the shingles. 

   Any additional help you can provide will be greatly appreciated!!  Is there some way I could talk with you?

   Thank you.

3. 
   DanH | May 25, 2018 05:37pm | #6

   One thing I'm not sure you appreciate is the difference between mold/mildew (fungus) and moss/lichen.  Encountering mold on exterior surfaces is actually fairly rare (at least in these parts).

1. 
   745sarachal | May 26, 2018 08:38pm | #7

   photos of our cedar shingles

   Well, you're right.  We have no idea if this is mold/mildew or imbedded dirt or moss/lichen.  We can't tell if it's growing on the stain, or on the wood.  Generally, once we get all the stain stripped off, they look pretty good.  I've put undiluted Clorox on a few areas and it gets rid of most of the bladk stuff  - but not all of it.  It still looks like there are dark areas on the cedar even after I clean it.  I hopefully correctly attached some photos.  We live in California about one hour Northeast of San Francisco.  Before I forget - I really like your Herman Melville quote. 

   The photos show the ugliness of our house.

   Thank you.

   
1. 
   DanH | May 26, 2018 09:14pm | #8

   Are those pictures AFTER you've used some sort of cleaner/stripper?  Did you scrub?

   Mold/mildew/moss/lichen would exhibit one common characteristic: being more concentrated on certain spots of the wall, based on exposure to weather and sunlight.

   Your finish looks rather evenly discolored.  Unless this is a result of your cleaning process, I would say the discoloration is due to the oxidation of iron and other minerals that are naturally found in red cedar and redwood.

   If oxidation is the cause of the discoloration, then a cleaner that uses oxalic acid (many "wood bleach" and deck cleaner products) will lighten things up significantly, while requiring very little scrubbing.  (Regular chlorine bleach, while effective on mold and, to a lesser degree, moss will have very little effect on oxidation-caused discoloration.)

   If you do use oxalic acid, be careful to keep it away from any anodized aluminum, and go a little easy on the cleaning, as wood in the redwood/ceder category gains much of it's durability from the minerals in it that ox acid will wash away.

1. 
   745sarachal | May 29, 2018 11:55am | #10

   BEFORE pictures - not after

   Thank you for your response.

   The photos are BEFORE any cleaning.  This is what happened to our house after too many years of not washing it down.  The Cabot stain is still on the house - along with all the mold/mildew. 

   I need to know if another oil based product is going to result in the same problem.  From what I've read, a water based product will be less likely to support the growth of mold/mildew, although the water based products will not last as long as the oil based stuff. 

   At this time, I just know that we don't want to have this happen again.  If we need to go with water based products, and they require more frequent application, we can live with that.

   Thank you.

1. 
   DanH | May 29, 2018 05:15pm | #12

   Once again, the staining seen in those pictures does not seem to fit the pattern for mold/mildew.  (Though it's impossible to say with certainty without a closer examination.)

2. 
   florida | May 30, 2018 07:00am | #13

   Jeeze, once again you step into the void. That looks exactl;y like mildew. My experience is washing well over 10,000 houses,

   miles of sidewalks and driveways and acres of roofs. What's yours?

3. 
   DanH | May 30, 2018 08:15am | #14

   My experience is watching people claim it was mildew when in fact it was efflorescence or oxidation or something else.  I've seen this several times, and there have been at least a couple of cases pictured here over the years.

   A quick test for mildew is to sponge on full strength chlorine bleach.  If there is a major color change in 30-60 seconds, without scrubbing, then it's probably mildew.  A slight change, with some scrubbing, after a couple of minutes then it's probably moss/lichen.  If the bleach has little effect (without vigorous scrubbing) then it's probably some sort of chemical discoloration.

4. 
   sawdust_steve | May 30, 2018 12:45pm | #15

   The best approach is try various washes and options on a concealed or less conspicuous area. Start ith the least abrasive  and work your way up.