en_tn_condensed/luk/06/48.md

dug down deep in the ground and built the house's foundation on solid rock

"dug down deep into the ground until he found a large, solid rock. Then he built his house on that rock so that it would be strong and stable." Some cultures may not be familiar with this process of building a house and may need to use another image for a stable foundation.

torrent of water

"fast-moving water" or "river"

flowed against

"crashed against"

shake it

Possible meanings are 1) "cause it to shake" or 2) "destroy it."

because it had been well built

This can be stated in active form. Alternate translation: "because the man had built it well" (See: rc://en/ta/man/translate/figs-activepassive)