You face the same problems you face everywhere with old houses, it is always a surprise once you start opening walls. Even the best built house, that stood for a 100 years, might have developed termite infestation in the last 5 years or a pipe started leaking in the wall last year and rotted something expensive.
Those are things that are completely apart from Chile.
Things I would expect in Chile among houses that old would be things like lead paint. Possibly pipes that are way pass their prime or have suffered earthquake damage over the years. Foundations and supports, although they might not have failed for 100 years, might not have completely missed the bullet with the last earthquake.
To look at any structure and say, "well it stood for a 100 years through all those earthquakes, it must be fine" with no more knowledge than that about the status and history, is to engage in the gamblers fallacy. Every quake is different, and every quake effects different buildings in different ways. It only takes the right one to effect the building in just the right way, for it to fail or be damaged. Especially when we are talking about structures that pre-date modern earthquake engineering.
I have had a look at a lot of old houses, some in the 150 year old range, and a lot of times just because it is old does not mean it is good. Once you start doing the costs breakdown, often building a replica from scratch would be half the costs of trying to restore it (because essentially you will be rebuilding it stick for stick anyway by the time it is all done).
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