(Please note that in certain situations,  what ,  when , and  where  can function as relative pronouns.) Relative pronouns introduce relative clauses, which are a type of dependent clause. Relative clauses modify a word, phrase, or idea in the main clause.
The 2014 Survey of Construction (SOC) from the Census Bureau shows that the average completion time of a single-family house is around 7 months, which usually includes around 25 days from authorization to start and another 6 months to finish the construction.
Finally, a stone house doesn't take long to build. Our walls went up in just eight weeks, and we moved in a short five months after beginning construction with 100% of the work having been done by Sharon and me, and our two girls (who were then 9 and 11 years old).