While building things is great, it isn't a substitute for weight training. If you are training for strength there is no substitute for progressive overload with barbell weights. The best part is that it isn't a tremendous time investment either. I train 3 days a week for about 3 hours at a time. I could possibly do it faster. That leaves plenty of time left to build things with your hands on your own land assuming you have the resources for that.
In two weeks I'll need help with 80 bags of cement. Loading them, unloading them, humping a barrow to the back of my property. There will be mixing and pouring and beer. I've already cleared the roots, shoveled Nd rolled the path, etc. So don't worry, the hard work is already done.
It is difficult to offer a reply to this comment because it is hard to tell what the intent is. It reads tongue in cheek to me. I apologize if that is not the case.
The work you are describing is difficult, but that doesn't mean that it will translate to absolute strength or that it is the same as strength training. Moving 80 bags of cement won't translate to deadlifting 405 pounds a few days later unless the person doing that is already very strong. If the person doing that work does not overexert themselves they'll certainly be adapted to doing more of that type of work though.
Strength training is about making deliberate progression through repeated cycles of overloading and adaptation, and not about making equivalencies from one type of work to another. A bag of cement in the United States weighs 94 pounds. If you move 80 of them, you'll adapt to moving 80 bags of cement that weigh 94 pounds. That will not translate to the ability to lift four or five bags of cement at a time without deliberate effort. Will you empty the cement into a container adding a little more each time with appropriate recovery periods between until you can lift four bags worth of cement? Or will you move them one at a time, or maybe two at a time if you are able, to get the job done?
I know you touched on it but the importance of consistent overload is paramount as well for strength and hypertrophy. 80 bags of cement won't cause adaptation unless it's a regular occurance.
Responding to both at once. Yes, lighthearted comment. You're right about adaptation. The point I'm trying to make is simple: building physical exertion into your daily life is the best way to retain strength, flexibility, health and mood as you age. The habits are easier to keep. Combine that with physical recreation and reasonable habits regarding food, drink, chemicals and rest.
It's entirely likely they do. However, the work done farming serves a different purpose than strength training. Farming requires the strength and endurance to do the work day after day, but there is no particular emphasis on strength beyond what is necessary to do the work. Training for strength differs because the emphasis is developing the ability to lift more weight each session. Endurance is not particularly important because the interval for training strength is short. 3 to 5 repetitions, followed by a break. Will a farmer be able to outlift a novice or even intermediate weightlifter? It's entirely possible. Will a farmer be able to outlift an advanced power lifter or olympic lifter who is approaching the top of they physical potential? Not likely. The farmer is adapted for a different type of work.