Expert article
Site supervision: duties, liability, and the checklist for practice
What is owed is supervision according to criticality, not permanent presence — and what was checked must be provable.
Expert article by Open Experience GmbH. · As of: July 2026
What is site supervision?
Site supervision (construction supervision) is the monitoring of construction work for conformity with the permit, the execution planning, the service specification, and the recognized rules of technology — the core of service phase 8 of the German HOAI ('Leistungsphase 8', the fee and service structure for architects and engineers). The site supervisor does not owe permanent presence but supervision according to criticality: simple work checked on a sample basis, supervision-intensive trades monitored closely. What they check, they must document — otherwise, in a dispute, they didn't do it.
What exactly does the site supervisor owe?
Case law requires supervision "to an appropriate and reasonable extent" — graduated by the difficulty and risk of the work. Routine craftsmanship calls for spot checks; critical construction stages call for presence. Whoever only sees the site fence from the outside is not supervising.
The individual basic services are covered in the guide to service phase 8 — including what has to be documented for each basic service.
Supervision-intensive trades — where you have to look
Work that experience shows to be damage-prone requires particularly close supervision. Here, case law demands heightened attention up to and including presence — and here the most expensive omissions occur.
| Trade | Why critical | What to document |
|---|---|---|
| Waterproofing (basement, roof, bathrooms) | Most frequent cause of damage, no longer visible later | Photos before closing up, connections and penetrations in detail |
| Reinforcement before concreting | No longer verifiable after concreting | Approval photos per section with date and location |
| Thermal insulation | Thermal bridges and moisture damage only show up after years | Document build-up, joints, and connections photographically |
| Screed | Build-up heights, edge strips, drying times | Measurement reports and approvals before flooring work |
| Building services routing | Collisions and leaks behind shafts | Leak tests, photos of the routes before closing up |
| Grouting and injection work | Result cannot be checked from the outside | The contractor's reports plus your own spot checks |
The liability trap — not the omission, the missing proof
In court, what counts is not how often you were on the construction site — but what you can prove. If a defect in a supervision-intensive trade surfaces years later, the site supervisor must set out how they supervised. Without a site diary, photos, and records of site walks, proper work turns into a lost case — including joint and several liability alongside the contractor.
The risk is real, the answer is simple: document what you do anyway — and in a way that explains itself later.
The duty checklist for every project phase
Four phases, four routines. Whoever sticks to them has the proof together at the end — without extra effort.
At construction start
Check the plan status, set up the list of parties, define the documentation routine — who records what, with what, and when.
Ongoing
Site walks with photo evidence, site diary daily, notify defects immediately (with deadline), evidence before building elements are closed up.
At acceptance
Accept formally, with a report, defects, deadlines, and express reservations.
Afterwards
List limitation periods, supervise defect remediation, hand over the documentation in full.
How the proof of supervision emerges along the way
Site walks, defects, site diary, and photos in one tool: every finding carries a timestamp, location, and responsible party — the file builds itself during the work, not afterwards.
Frequently asked questions
Does the site supervisor have to be on the construction site daily?
No — what is owed is supervision according to criticality, not permanent presence. For supervision-intensive work, the duty intensifies up to presence.
Is site supervision the same as construction management?
No: site supervision is service phase 8 under the HOAI (private law, for the client); the construction manager under the state building code bears public-law responsibility. The roles can coincide.
Is the site supervisor liable for the companies' execution errors?
They are not liable for the error itself, but for failing to detect it if proper supervision should have revealed it — often jointly and severally.
How do I prove supervision?
Site diary, dated photos with location reference, documented site walks and defect notices — created continuously, not reconstructed.
What does poor documentation cost?
In the worst case, the lawsuit — and before that, the fee: missing basic services such as the site diary justify a reduction.
Keep supervising as you do — prove it better.
45 minutes on your project: site walk, defect, deadline, proof — in the real workflow.