Q: The east-facing railing at my home is topped by a 2-inch-by-6-inch piece of redwood, which has always been painted with a dark brown latex paint.
One 12-footer out of a total of about 92 feet of railing top will not retain its finish–the paint cracks and peels.
The house (and railing) was built in 1963. In the 34 years we have lived here, I have repainted that railing three times.
About six years ago, I noted that the surface of this one 12-foot-long 2-by-6 was cracking and peeling. I planed the surface down to bare wood. After priming it and letting it dry thoroughly, I painted this piece with a top-grade latex paint.
Two years later, the finish started peeling again. I repeated the procedure: plane to bare wood, prime, dry, paint. This year, the finish is cracked and peeling again.
No amateur or professional I have asked has had any notion what could be wrong. The problem did not start until about 25 to 28 years after the house and railing were built.
Do you have any idea what started this problem? What keeps it repeating?
A: We think you have a piece of lumber that is delaminating. The grain is flat or tangential, and the exterior layers are peeling. The cause could well be the natural expansion and contraction of the wood due to moisture over time.
Boards with a flat grain are cut from the outside of a log that is “plain” sawn at the mill. This means that the log is placed in a carriage where the entire log is sliced into boards. Boards cut from the center of a log have more of a vertical grain, whereas boards from the edges tend to have a flat grain.
Boards with tangential grain tend to be less stable and also react to changes in moisture more than vertical-grain boards.
Logs can also be quarter sawn. This timber is cut in quarters and then sawn in such a manner as to produce mostly vertical-grain boards.
As to why, after so many years and several paint jobs, this board failed now, we don’t know. Rather than continue to fight it, we suggest you replace it.
Buy a piece of 12-foot, 2-by-6 redwood that has a vertical grain. That is, the grain runs as much as possible in the 2-inch direction. Take it home but do not install it immediately. Place it on edge on the east side of your house for 4-6 weeks so that the moisture content of the wood will adjust and stabilize to the conditions where it ultimately will be installed. After allowing it to acclimatize, cut it to length, prime it, paint it and install it.
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