Concrete, gypsum and steel are primarily domestically produced. Similar goes for wood (although a substantial amount is imported, e.g. from Canada - the tariffs range from 25% to 50%). Labour & Materials may make up say 60% of the cost of a house, but only 50% of this is likely materials, with likely a minority of the materials tariffed.
What is likely to actually reduce rent and house prices is making development permission and laws more lax, as well as preventing rent control.