Witness stakes (reference stakes) are set at a known offset from a layout point so the layout can be re-established after construction activity destroys the original. Set at least two witness stakes per critical point, at different azimuths and distances so you can recover the point from intersecting measurements. Record the offset distance and direction on each stake lath.
Why Witness Stakes Are Essential
On any active construction site, layout stakes are destroyed constantly — by equipment traffic, by grading, by trench excavation. If the only record of the design point location is the original stake, losing the stake means losing the point. Witness stakes let you recover the original location from surviving stakes without a full re-stakeout from control.
Witness stakes are especially critical for: building corners before foundation excavation, alignment control points that will be disturbed by grading, pipe laser instrument setup points, and any layout point that took significant time to establish.
Setting Witness Stakes
- After setting the original layout point (hub with tack), set at least two witness stakes at different azimuths, typically 5–10 ft from the point in directions where they will not be disturbed.
- Record on each witness stake lath: the original point ID (station, corner number, etc.), the offset distance, the direction to the original point, and the date set.
- For critical points (building corners, alignment control), also photograph the witness stake setup showing all stakes and their relative positions.
Recovering a Point from Witness Stakes
To recover an original layout point after the original stake is destroyed:
- Find two surviving witness stakes for the same original point.
- Tape from each witness stake in the recorded direction at the recorded distance. The intersection of the two measurements is the original point location.
- Verify by checking with a third witness stake (if available) or by shooting the recovered point from the total station to confirm it matches the design coordinates.
When Witness Stakes Are Destroyed Too
If both witness stakes for a critical point are gone, re-stake from control using the total station and the design coordinate file. This is slower but unavoidable. Keep the project coordinate file backed up in the office so a re-stake is always possible even if all field stakes are gone.