Yes, the 1960s and 1970s were pretty much the low-water mark of building quality, I think (at least in the UK). Thousands of new homes were thrown up across the country at maximum speed and minimum cost. My house was built in 1964 and the construction quality is pretty terrible. The mortar joints between the bricks vary between about a quarter of an inch and two inches where they had to fudge the wall because it was going out of true. When I replaced my kitchen a couple of years ago I had to do all sorts of fiddling and packing-out of the units because the “rectangular” room was actually a rhomboid. Even now you can see that the units along two of the walls are several degrees out of parallel with the floor tiles. If I’d built the walls out to be perpendicular then I’d have lost several square feet of floor space!
As others have said. surviving 200- and 300-year-old houses are generally very solidly built, and, because they are often the more expensive properties, they have usually been renovated carefully.
I’ve been doing some googling as this thread piqued my interest, and I’m sorry if this is a bit of a hijack, but what is the oldest house in America that is still privately owned and actually still used as a residence and not say, a museum? I’m not having a lot of luck.
Our second 1920 had 3 or 4 additions, no problems with any of them for the 13 years we lived there. It’s something to watch out for, but not necessarily a deal-breaker.
In the States, aluminum wiring is a big problem with houses built between 1965 and 1975. It’s not that there’s a problem with aluminum wiring by itself, but rather, where aluminum meets copper. It’s very difficult to find switches, dimmers, circuit breaker boxes, and the like that are safe to use with aluminum wiring.
Also, 1960s and 1970s-era interior design is perhaps the least admired. Dark kitchens, dark paneling, shag carpeting, wallpaper with metallic or loud patterns, intricate Rococo-style ornamentation, a lot of orange and avocado green, and the like are very common. If you live in the Rust Belt or an area where there’s a lot of elderly folks, prepare to encounter a lot of 1970s kitchens in your househunting adventures, even in 1950s ramblers, 1930s Capes, 1920s Craftsman bungalows, 1890s Queen Annes, and 1850s Greek revivals.
Size is one thing, but it can be more challenging to find a pre-WWI house with a floorplan that isn’t awkward, or at the very least with some complications.
The area I live in is absolutely silly with 1800s-era cottages and farmhouses. I wouldn’t live in most I’ve stepped foot in. Stairways are narrow, and treads are often short and steep. Bathrooms are usually far removed from bedrooms, typically right off a living room or kitchen. Kitchens are usually sited in a way that forces awkward placement of counters and appliances. Some have bedrooms that are only accessible from other bedrooms. Ceiling height is often low, and the floor level can vary from room to room.
“Victorian” (Queen Anne, Eastlake, Romanesque, Shingle, etc) houses aren’t nearly as bad, but the floorplans of many were shaped by the rituals of the day. Houses from the era are often chopped up into a number of small rooms and parlors. Opening up the floorplan can be a challenge, because most internal walls will be load bearing.
I asked my home inspector a similar question before we purchased our 135 yr old home. His words, " A house that stands a hundred years will stand two, if it’s maintained, even minimally. Not many new built houses will be standing in 100 yrs from now no matter how much maintenance they get, from what I routinely see."