Funny that 1500-1700 square feet is "smaller" here in the US. A little perspective: in most European nations, that's a BIG house. For example, the typical middle class French house, out away from the big cities where land is more affordable, is still only 800-1100 square feet. A 1500 square foot house for sale there is advertised as "for big families."

But to get to the gist of things here, your 1920s house will be a fundamentally sturdier and longer lasting house than anything being built today. Modern lumber can't come close to the dense, solid old growth wood that was used in houses then. I know, I've drilled into both!

Current lumber is softer, more flawed. Just look at a house under construction. Many dimensional boards supplied are warped, bent, scarred with knots. I've seen evidence of previous insect infestations.

Even modern lumber's nominal dimensions are smaller than in the old days. And sometimes they cheat even that; I've bought lumber in the last few years and had to adapt my projects to the lumber's actual dimensions, a fraction of an inch smaller than the supposed nominal.

Old houses were designed to be plenty strong, by architects with seat-of-the-pants experience. Modern architects use computers to adopt the cheapest, lightest, flimsiest materials and design that will still hold the house up. It's all about a low price while still maximizing return for the builder and his investors. Wall Street requires it.

I expect that your 1920 house will still be standing proudly a couple hundred years from now, when the newer houses around it have fallen down, or been torn down to be rebuilt.