If you need something in a hurry try a web search for english manor floor plans. They won't have a grid, but most will have room sizes so overlaying a grid is easy. They also won't be as good as a home-made plan because they're generally missing secret doors and such, and the layouts aren't always good for adventures.
I use them for inspiration and to add a bit of realism to my maps. Sometimes I forget to add rooms that some might consider critical, like kitchens, closets, bathrooms.
