We have a strong-willed eight-year-old son that occasionally wets his pants (once every two to three months when he's too busy playing and the like). Recently, after a wetting episode, I decided to discipline him by diapering him. My wife felt it was not appropriate, and that I should just increase the severity of the spanking given to him. I thought perhaps, a different method would make more of an impact. Was I out of line?
You have the right idea when you thought to use a different tactic, but your choice won't lead to the conclusion you desire. First, let me make it clear that I am not opposed to spanking. The Scriptures teach that it is an effective method for dealing with foolish childhood behaviors. The problem is that sometimes we parents tend to get stuck in a rut. Since spanking works for one set of problems, then it must be the best solution for all problems; but that is not necessarily true. I recommend reserving spanking for willful behavior. You know it when your child looks at you as if to say, "I know its wrong, but I'm doing it anyway." I also recommend it for dangerous behavior, such as a child reaching for a hot pot, or a child who is destroying property. You want the child to know the action is wrong right then and now -- before something worse happens.
In your case, you are not describing deliberate defiance. Your boy is not wetting his pants to get back at you. You describe him as strong-willed, but in this case I would argue that his will is not directly involved. Instead you are describing a boy with the ability to strongly focus on a task that he likes, to the point of not noticing even his own body signals that his bladder is over full. The joy of what he is doing exceeds the need to temporarily interrupt his activities to use the toilet.
While wearing a diaper would be embarrassing for an eight-year-old, it won't have a large impact. Since his pants cover the diaper, it is simply uncomfortable and soon forgotten. In addition, it removes all need to run to the restroom. So what if he has an accident? The diaper will catch it. Meanwhile, he can continue with his absorbing activity.
What you need is something that makes the cost of wetting his pants exceed the fun of his activity. Allow him to dress normally (no diaper). Get a large pail handy. The next time he has an accident, calmly take him to the bathroom, have him strip down and show him how to thoroughly wash out all his clothing in the pail until all urine and smell is removed from his clothing. Once he is shown how to do it, don't stand over him, let him do the task on his own. Require him to ask you inspect his work when he is done. If it is not up to your standards, show him what he missed and have him do it again. If his accident caused other things to get urine on them, show him how to clean it up and then inspect it for cleanliness. Once his clothing and anything else are adequately cleaned, have him bathe himself thoroughly. Again, don't stand over him, but he has to check with you that he is completely washed. Then have him dress in his pajamas and stay in his room the rest of the day (only coming out for meals and using the toilet). Do this even if the accident happens early in the morning. Right after supper, he is sent to bed.
You don't have to raise your voice or become frustrated. It is simply the rules he will now have to follow. If he breaks these rules, then a spanking would be proper because you are now dealing with defiance. Once the spanking is done, he is to continue where he left off. If you and your wife calmly and consistently apply this system, you will manage to harmlessly make your child's life miserable each time he forgets to pay attention to the call of nature. (Notice that this effectively cuts him off from his absorbing activity.) Since the accidents are infrequent, don't expect a quick cure. However, it won't take very many scrubbings followed by nothing to do before he will find his own motivation to pay attention to his bladder. You are firmly moving the problem out of your court and into his.
By the way, to get urine smells out of things like carpeting or upholstery, my wife and I found that the products made to clean up after pet accidents work wonders. Some, like Nature's Miracle, even work on other disgusting things like vomit that leave lingering smells.