Your photo is not sharp enough to show what the issue is, but I suspect these are cheap replacement doors that were installed at some time and are not of the same quality as the originals. An 80-year-old house would put it in the 1940's, and interior doors then were often not hollow core and were of better quality in any case.

Yes i did my math wrong the house is 70 years old….i know hollow core doors are very cheap and prone to holes easily, i just havent seen anyone else in ny research have entire vertical strips like this of damage.

were going to replace then anyways, im just cutious how damage like that happens

“i know hollow core doors are very cheap and prone to holes easily”

Neither of these things are really true. Hollow core doors are much more economical, but that doesn’t make them very cheap. They are not prone to holes easily unless someone in your household is prone to punching them and hollow core doors are cheaper than ER visits so maybe that is a good thing.

If you want solid doors then great, I have them in one house and there is nothing at all wrong with paying the significant premium for the heft of solid core doors. However, hollow core doors will last a lifetime when properly maintained and proper maintenance is the same as solid core doors.

As for what likely caused the damage…I am not sure it matters. The important question is how likely are you to repeat that damage, which is information that you have better access to. If you are rough on your doors, solid core will be more durable but much more expensive to replace.

Agree with Sigrid: dog.

Im not a pet person so i didnt even think of that! but makes sense.

i know it doesnt matter the why since im going to replace them anyways- was just curious, really really appreciate everyones thoughts! Thanks Bry for your advice on solid vs hollow, im a new homeowner so my assumptions were wrong. will definitely consider hollow based on prices

I have some doors of a similar style and vintage. It was the fashion of the day. :)

It seems like little damages add up over the years. Teenagers, furniture moving, pets, carpet catching the bottom, etc...little snags become big snags...