r/HouseSubsidence

We're currently planning a renovation and had two bore holes drilled at the back of the house for soil testing. Just got the report back and the recommendation was underpin one side of the house with deep screw pile underpins to at least 3.5m. Although not specifically in the report, the engineer mentioned the large tree in the backyard has roots going at least as far as bore holes he drilled by the footings.

I'm questioning all of this because the back (new) part of the house is 25 years old and there is very minor cracking to the existing brickwork. Essentially a single crack above a window that has stayed about 1-2mm wide for as long as we've owned the place (2.5 years). If we weren't planning on doing renovation and replacing some of the brick wall with a glazed door, I'd be happy to just watch and wait. If underpinning is the right choice then I'm happy to do it, but my understanding is that partial underpinning might actually worsen differential movement and cause even more cracking. Also the report itself said that there was no risk of load bearing capacity being impacted by the current soil condition.

What are my options here? Is it worth getting a second soil test and geotech opinion?