Textured walls are not an indication of the age of the house, but of home trends in certain geographical areas. Texture should be consistent throughout the house. Since your ceilings are all finished in knockdown texture, continuing that throughout the house would be the least expensive fix. Go with what you like, what is typical in your area, and what your budget allows.

Knockdown Texture

Old World Texture

Hi Ria, to elaborate, something "simple" like changing drywall texture is done all the time. You rip out all the drywall and start from scratch. That is incredibly labor intensive and there is a long long list of other things you might do/need to do anyway with the drywall out to bring your home up to date. Ends up being a whole house remodel really, assuming you can work your floorplan into the style you want. If the floor plan doesn't play well, now you are looking at modifying structural members. Retrofitting an old house is always 10x more labor intensive than starting from scratch. If you are able to provide most of the labor and knowledge, you may be able remodel a whole house with 5 to 10 years of hard work (I've seen this done). It's the reason why many folks in my neighborhood end up buying old run down homes for $1.3M and completely bulldozing and building from scratch. It's cheaper and you get what you want. Hope that helps.

Changing drywall texture should not require replacing the drywall unless it is badly damaged. Sanding down the old texture or adding a new skim plaster coat, followed by the sprayed-on texture coat should suffice. The knockdown texture is very forgiving.

That is a lot of work for a whole house...would be less labor intensive to redrywall. Not to mention the amount of effort to get those walls nearly perfectly flat...just thinking of it makes me tired. Full disclosure I am not a drywall expert, but I know enough to know there is a very good reason it is not common practice to plaster a whole house to remove texture. Just my opinion of course. I've seen crazier things done.

To those who are suggesting that all textured walls must be redone/replaced, PLEASE consider the location of the house in northern California. Textured walls are quite common in western states and do NOT date a house. The wall texture, however, should be consistent throughout the house. Focusing on redoing the texture only in the rooms that are different, rather than redoing/replacing all the walls in the house, will free up money for other improvements likely needed in a 47-year old house.