I built the house we live in from lumber I salvaged by tearing down several small buildings I bought at auction on some expropriated property. I laid it all out (I had 2x4's ranging from full dimension rough sawn to modern planed two by's and a couple sizes in between), figured what I could build and started sawing and hammering. I was able to add two offices and a bathroom to the 12x18' cabin that was on the property when we bought it. A few years later I bought finished lumber to build on a two-story extension and again a number of years later built a stand-alone 20x20' two story storage, tool shop, two-studio building with full size attic (I hated the waste of space made by the trusses I'd installed on the extension, so I built the roof on this building with open joists). I still use a hammer, not a nail gun, but I do use a fair number of power tools and have always used a circular saw. I built everything with no help and no plans. That's how I do most things. We've lived in the house for 30 years and there are only a couple of leaks that I'll get around to fixing before I die, possibly.
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WELCOME to the forums, if I forgot to say it!