The pilot of a tailwheel aircraft lost control and departed the runway surface when the aircraft veered right after tailwheel touchdown. Possible cause was reported as loss of tailwheel spring.

Narrative

Landing on private grass airstrip in tailwheel aircraft. Landing on runway with tailwind of reported 5 MPH (from 250). This was preferred runway established by radio contact with ground personnel. Runway is an uphill grade and therefore the preferred landing runway unless wind conditions too strong. Approach and landing initially uneventful. Was performing a two wheel landing and had increased my approach speed some to compensate for tailwind conditions. Touchdown was uneventful (no bounce; straight down middle of runway). Rollout going well until tail dropped. When tailwheel contacted the ground; aircraft suddenly veered right and did not correct with first full left rudder; then left braking. Aircraft was too slow and mis-aligned to apply power and power out. Sides of runway have a downhill slope and runway is somewhat narrow. So aircraft was immediately traveling off runway downhill. I was braking and trying to rudder left without success. Airplane first contacted bushes (with a prop strike to bushes) and left wing hit a tree with outer leading edge. Right wing tip came to rest on outside corner of a building. No damage to building or tree; only two shrubs/bushes damaged. Airplane damaged on both wings; left wing strut; and prop strike to engine. No physical injury to me; the only occupant. Inspection following the accident revealed a missing tailwheel spring. The tailwheel did not contact anything during the event. Also; on pre-flight inspection the tailwheel springs were present (my tie down of the tail is immediately under them; and they are very visible when untying the airplane). Spring must have been lost prior to landing and accounts for the sudden veer right when the tail touched down. Of Note: A very seasoned pilot on the ground witnessed the entire event and confirmed to me that all was looking good until the tail touched down and the aircraft veered right suddenly with the tail touchdown.