Redwood and Cedar Stain Removal
When it comes to wood siding, you will not find much better than cedar or redwood. Both types of wood are durable, strong, insect resistant, and they look fabulous. Because cedar and redwood are such great choices for siding, we see many people going this route. However, just as with any type of siding, even cedar and redwood can experience stains.
For instance, let us say you had redwood siding with a light but solid colored stain. If you had stains, you might begin to notice brown streaks running down the side. Sometimes, siding stains such as this actually look as if they are coming from the backside. Other times, you might notice bluish/black stains at the location of the screws and nails.
Unfortunately, this phenomena is known as "extractive bleeding", which can occur with cedar, redwood, and other types of wood siding. The reason is that both cedar and redwood are from the forest. Because of this, they contain chemical extractives that occur naturally. Sometimes, the stains seen on cedar and redwood especially could be from water. If any moisture or vapors condensed on the backside of the siding, it would penetrate the walls, thus causing the problem.
If the water traveled on the siding and then dissolved some of the extractive chemicals, the water would likely create a break through in the siding's seam. However, as the water evaporates, the remnants are the spots see. In addition, if water were to go through the wood's surface, it would naturally soak into the wood, which again, would cause the chemicals to dissolve, drawing them out through the surface, and leaving spots.
Another common problem has to do with the nails. For instance, these same chemicals would likely cause problems with the iron in the nails. Therefore, any wood siding installer should know to use only stainless steel or galvanized nails on cedar and redwood to eliminate this risk. However, if iron nails were already used, another option is to have them countersunk, after which time the holes would be filled with high quality water repellant. Then once the repellant dries, exterior wood filler would go on top.
Keep in mind that in many cases, these types of stains can be removed. For instance, in a bucket, you could mix one cup of trisodium phosphate with one cup of bleach and one cup of water. Using a cloth, you would clean the spots on the siding. After washing down the siding area affected, mix another solution of four ounces oxalic acid crystals with one gallon of warm water, which would be used to wipe down the area again. Once dry, you would rinse the siding with regular water.
The best way to eliminate this problem occurring in the first place is to have the wood siding sealed. However, rather than having, the wood sealed after installation, each panel or plank would be sealed prior to installation.