Painting the Home, Exterior Spaces: The Front Porch Part 2

We just completed a very large porch project.  Upon inspection, we found a 14 year old house with the original polyurethane on the Beadboard ceiling.  The home owners wanted to restore the original natural wood look, but mildew developed between the poly and the wood.  What do we do?

 

After talking with the homeowners a bit more, we understood that they tried to power wash it the previous summer and they sanded a few patches, but since this was labor intensive, they did not get too far.  Yes, you can clean up the mildew, but you have to get to it first and that means sanding of the polyurethane.  The homeowners took all the right steps to evaluate.  Our recommendations were sanding or replacing the wood, but both were more than the homeowners wanted to spend.  The solution was to paint.

 

Why did mildew develop between the poly and the wood?  We have seen this before in polyurethane coated ceilings, picnic tables and in other areas.  Wood has moisture when installed.  I suspect the hidden or underside of this wood was not primed.  Since the wood can not breath as effectively under a polyurethane coating, its moisture is a perfect environment for mildew.  To avoid this, the best you can do is install kiln-dried wood and prime the hidden or underside before installing.  In the long run, mildew may still develop, but these 2 steps should keep the desired look for a longer period.