The dead were not buried under houses.
It was seen as very dirty to live among those in Sheol.
Actually; it's a violation of burial laws.
That passage that you are looking at is the common manner in which they referred to their family "tombs", or more properly thought of as familial entrances to Sheol.
That "house" is the Sheol house of the family where one goes to lay with their Father and their Father's Father, etc...
There are countless burial cave infrastructures exterior to the village or city boundaries of the same time periods.
To be more to the point, looking at this with practical biological thought: it would be really disgusting to keep the body in your house, anywhere, because the rotting corpse in the non-air-conditioned, yet extremely hot climate would be extremely foul and be really unsanitary.
The infant bones under houses in jars practice is very likely a taboo practice (at the time, but not earlier and earlier was done on large mounds and not hidden under houses) by remnant followers of a fertility Goddess of 'Ashtart.
See: The Biblical World, Volume 36. The Cult of the Mother Goddess, round about page 33/34 area.
I found a copy on Google Books so you don't have to buy it:
http://books.google.com/books?id=qY7NAAAAMAAJ&printsec=frontcover#v=onepage&q&f=false