I don't see why your project was self-defeating: since you no longer have scrap wood cluttering your garage, it seems it was actually self-fulfilling. But I think the self-contradictory part comes into the consideration of whether you've built a scrap-wood storage system. Clearly making the shelving eliminated the need to consider the question since the solution itself did away with the need to consider the problem. When a question is an academic enterprise, devoid of practical consequences, it is called moot. When an activity makes itself a moot consideration, it is called self-mooting. Consider this example from a motion from a long-suffering defendant in a law suit who complained that the plaintiff had decided to
prevent the deposition from going forward by filing this patently frivolous, self-contradictory, self-mooting motion by which Plaintiffs are moving on May 10, 2011 for an order retroactively preventing a deposition from taking place on April 19, 2011, when the deposition already has to be rescheduled because they blocked it by filing this motion.
As far as I can tell, the motion is frivolous because it seeks to prevent a deposition from taking place after the deposition had been cancelled. This had the effect of blocking any rescheduling of the deposition since the rules of civil procedure require that the parties to wait for the court to consider the motion. Once the defendants got the delay they wanted by filing the motion, there was no reason for the court to consider the merits of the motion, making the motion self-mooting.
Here's another example from the December 1989 issue of Spy magazine (which I still miss):
Infamy has become a self-mooting concept.
This is from an article by Richard Stengel called "Here Today, Here Tomorrow" on why we can't seem to get rid of celebrities. Even disgrace cancels its own opprobrium with the glamor of the fame it induces.
Finally, an example from the website The DailyKos about the 22nd Amendment to the Constitution of the United States, which forbids anyone from being elected President more than twice. Some people claim that the amendment does not preclude a President who has been elected twice (e.g, Bill Clinton or Barack Obama) from serving a third term by being elected Vice-President on a ticket with a Presidential candidate who immediately resigns upon election. This would allow the Vice-President to assume the office of President a third time by succession, not election. A commenter notes that this interpretation
... requires a claim that the language of the 22nd [Amendment] was
drafted so as to make the provision essentially self-mooting....
Legal interpretation generally holds that provisions of the law not be interpreted to be self-defeating.