As with any building, home extensions can be affected by subsidence which can crack walls and cause doors to become misaligned. During the planning process, your builder and architect should discuss the site with you and put in place appropriate foundations to provide the most stable base possible to build on.
What to do if extension subsidence occurs?
You should consult with a structural engineer to assess the extent of the damage and recommend appropriate repairs.
You can learn more here: https://forums.moneysavingexpert.com/discussion/6322654/possible-subsidence-to-extension-how-concerned-should-i-be-please-help
