Okay, so your step #1 for building a 1000 year house is to just... have a house that never has any leaks or termites? I can see some issues. If you want somet

Okay, so your step #1 for building a 1000 year house is to just... have a house that never has any leaks or termites? I can see some issues. If you want something to last, you plan for when it does go wrong. You should be designing a house that survives ten once-in-a-century floods and storms. Freezing pipes. Hot and cold. Termites, carpenter ants, mice. > ... which also means that unburied steel, protected from elements, up in the air, is going to last more than 1000 years. Rust is protective. That's why cars can rust so quickly, because vibration breaks the rust flakes off and exposes steel to more air and water. Steel beams are subject to bending and vibration. Steel buried underground is not. A larger problem is also that rust is expansive. I'm not positive what you mean by plate connectors, but nailed tie plates push their nails out over time. Screws and bolts work fine. The biggest problem comes with using treated wood and steel together. Treated wood, even the non-arsenic ones, use copper compounds. That causes galvanic corrosion. It'll even eat through zinc-coated steel. Galvanized steel is enough for at least a couple decades, but I have no idea about a millenium.