Bottom piece of exterior trim is rotting away. Window is on the western side of the house with full sun exposure for the last half of each day. This trim is ten years old. Two other windows on this side of house, only one of which shows some rot (not nearly as much).
What do I need to do and what do I need to look for to determine the scope of the problem?
Framing the floor inside a crawlspace foundation keeps a gable-end addition close to grade.
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Replies
This looks like cheap white pine flat lumber, probably not backprimed or sealed properly, not that it would have helped a lot since white pine just loves to rot away. I'd replace it with something better like PVC trim.
Trim on the west side of my house did that in about a year. I'm not much of a painter and a western exposure can be very significantly more detrimental than e.g. a southern exposure (i.e. suns rays are more direct). Unless you have reason to believe you have moisture issues (e.g. prevailing winds blowing rain on that orientation), then your situation is not surprising.
Someone may chime in w/ a how to on painting application that will maximize your durability. A sloped Piece of trim might be good to drain the water better rather than allow it to sit on the top of the trim.
Drainage?
It appears to be a slider - correct? Assuming yes, there must be some kind of drains in the bottom tracks. Where do those drain? Perhaps the windows were not really made to be 'captured' around the perimeter with trim and the drains are actually draining on top of and/or behind the trim boards.
Take a closer look - both from inside (with window open) and from outside.
The western exposure is significant, but exactly why depends on the weather patterns for your location. Here, for example, most storms approach from the south west. My bet though is that windows on other sides of your home all have the same problem, they are just not is such an advanced state of decay - YET.
Sometimes a piece of wood is just bad, but that storm/screen may be adding to the problem by trapping water and letting it pool up.
Replace the wood. Prime the new pieces with alkyd exterior primer and paint with good acrylic latex on all six sides before installing. Drill weep holes in the storm/screen (or clear the ones that are present) so that water can drain out. (It looks like there might be drain slots, but not at the very bottom of the storm frame, some water can still pool. If so, fix that.)
How about Trex?
There was someone here who used to make window sills out of that Trex deck material. It should be invulnerable to rot and termites, not sure how you paint it, though.
-- J.S.