past perfect:
The Smiths hadn't built their house four years.
Had the Smiths built their house four years?
past perfect continuous:
The Smiths hadn't been building their house four years.
Had the Smiths been building their house four years?
past perfect:
The Smiths hadn't built their house four years.
Had the Smiths built their house four years?
past perfect continuous:
The Smiths hadn't been building their house four years.
Had the Smiths been building their house four years?