Where does To Kill a Mockingbird describe the Finches' house?

Jem and Scout’s house is on the main street in town.

 Jem and Scout are fairly well-off.  Their father is a lawyer, and they live in a nice house on the main residential street of Maycomb.  People coming from the country have to pass it.  There are a few places where the house and neighborhood are described. 

When I was almost six and Jem was nearly ten, our summertime boundaries (within calling distance of Calpurnia) were Mrs. Henry Lafayette Dubose’s house two doors to the north of us, and the Radley Place three doors to the south. (Ch. 1) 

There is a treehouse in the backyard.  From the treehouse, Scout can see the schoolyard.  Behind the house is a Deer’s Pasture, and then the schoolyard (Ch. 6).  The Finches' house is large enough that Scout, Atticus, Jem, and Alexandra all have their own rooms.  Every room seems to have a fireplace too (Ch. 8).  There is also a carhouse. 

Scout describes the house’s foundation when she thinks there is a snake under her bed (it is actually Dill).  The house has no cellar and is “built on stone blocks a few feet above the ground” (Ch. 14).  When Scout walks Boo Radley home, she describes her house from his porch. 

There were Miss Maudie’s, Miss Stephanie’s—there was our house, I could see the porch swing—Miss Rachel’s house was beyond us, plainly visible. I could even see Mrs. Dubose’s. (Ch. 31) 

There are steps leading up to the house, because it is raised on stone blocks, and there is a front and back porch.  Scout and Jem sometimes sleep on the back porch in the summer, which is screened in. 

In case you are referring to the Finch family house at Finches’ Landing, there is a very good description of it in Chapter 9.  It is “a two-storied white house with porches circling it upstairs and downstairs” with “six bedrooms upstairs,” but the daughters’ staircase was in the parents’ bedroom so they would always know where they were. 

There was a kitchen separate from the rest of the house, tacked onto it by a wooden catwalk; in the back yard was a rusty bell on a pole, used to summon field hands or as a distress signal; a widow’s walk was on the roof, but no widows walked there … (Ch. 9) 

The Landing is off a river, and described as “self-sufficient.”  Scout visits it with her family during Christmas and a few other holidays.  Aunt Alexandra and her husband live there.