Expert article
Preventing defects: the timing costs more than the fault
A connection set in the wrong place is a minor matter on the day it is installed. Once the screed is down it is a building operation; after acceptance it is a case with a solicitor attached.
Expert article by Open Experience GmbH. As of: September 2026
Why is preventing defects cheaper than putting them right?
Because the cost of a building defect depends not on its nature but on when it is discovered. As long as the element is still accessible and the firm is still on site, the correction is a piece of craftsmanship. After that come access, the follow-on trades, delay to the programme and finally the question of responsibility — and once the works have been accepted, the client carries the burden of proof (§ 640 of the German Civil Code). Every stage later multiplies the effort, without anything changing about the defect itself.
Legal framework: Germany (Civil Code BGB, construction contract rules VOB/B, fee schedule HOAI). Other countries have different rules, and contractual agreements take precedence over the standard periods named here.
The same defect at five points in time
The table does not describe an exceptional case but the normal course of a wrongly executed penetration.
| Discovered | What has to be done | Who carries it |
|---|---|---|
| *During installation* | Set it again, within the same working hour | The subcontractor, without discussion |
| *Before closing up* | Rework and one additional visit to site | The subcontractor, plus the scheduling effort |
| *After closing up* | Open up, rework, reinstate, follow-on trades | Disputed — several parties involved |
| *At acceptance* | Reservation, deadline, remedial work under time pressure | The contractor, if the reservation was declared |
| *During the defects liability period* | Notice of defect, evidence, expert, often a building in use | The client has to prove the defect |
The jump between rows three and four is the largest one: from acceptance onwards it is no longer about craftsmanship but about evidence.
Why defects stay undetected
It is rarely the difficult details that slip through. It is the places where nobody was responsible, where the deadline was pressing, or where the information never arrived.
- Nobody saw itDuring the walkthrough the area was obstructed, locked, or work was in progress — and by the next visit it was closed up.
- Someone saw it but did not record itThe remark was made verbally, and the person who heard it was not the person responsible.
- The preceding work was not soundAnyone building on an out-of-true substrate produces a defect they did not cause.
- The operative did not know any betterConnection details that exist only in the designer's head do not get built correctly by chance.
- The deadline mattered moreUnder pressure people carry on building instead of stopping — that is a question of leadership, not of software.
The site diary is a tool for prevention
The site diary is regarded as an instrument of proof, but above all it is an early warning system. If you record every day which firm worked where and with how many people, what the weather was and which obstruction was reported, you see deviations before they turn into programme problems — and programme problems are the most common cause of hasty workmanship.
- Obstructions visible earlyA piece of missing preceding work that appears in the diary three times is no longer coincidence but a pattern.
- Weather without manual effortFrost periods and rain days turn up later in every discussion about variations — if they are captured automatically, they are correct too.
- A daily report instead of recollectionEntries made on site contain details that nobody can recall by the evening.
Inspection and diary interlock
Taken separately, checklists and the site diary are two documentation duties. Together they form a system: the checklist says whether an element is sound, the diary says under what circumstances it came about. Only the two together explain why a trade stands out — and supply the basis for planning the next section differently.
A rule from practice: an inspection result without context explains nothing. A daily report without an inspection result proves nothing.
Five habits that get expensive
A walkthrough without a route
Walk the same accessible areas every time and you will always find the same defects.
Sign-off by shout
"You can close it up" is not an approval but a later problem of proof.
The diary on a Friday
Five days in retrospect are an essay, not a site diary.
Defects left until acceptance
Collect them up and you end up negotiating over a list instead of over a building element.
Repeat defects without consequence
The same defect in three flats points to the detail, not to the tradesman.
Better
Fixed inspection points, fixed walkthrough routes, daily entries — and an evaluation that somebody reads.
A daily report that arises along the way
With Construction Diary the entry is made as you go rather than in the evening: weather and walkthrough data are carried over, everyone involved keeps their own diary, and from that a joint daily report is formed. The system reports open tasks itself — the most common cause of gaps is not reluctance but a forgotten day.
Frequently asked questions
Can the benefit of preventing defects be quantified?
In an individual case yes, in general terms not credibly. What can be compared is your own track record: the number of defects at acceptance, the number of remedial appointments, the number of cases in the defects liability period.
Isn't preventing defects the contractor's business?
Defect-free work is what the contractor owes. Site supervision nevertheless owes monitoring of its own — and carries the risk where that monitoring was omitted.
Which trades need the closest monitoring?
Everything that gets closed up or draws consequential damage after it: waterproofing, thermal insulation, reinforcement, fire stopping, connection details.
How often should walkthroughs take place?
As often as the state of the works changes. Daily while elements are being closed up, usually weekly during fit-out — fixed appointments beat spontaneous walkthroughs.
What is the point of evaluating inspection results?
It shows up repeat defects. The same inspection point failing in several units points to a detail, an instruction or a briefing — not to an individual tradesman.
Where do you start if none of this exists?
With the two building elements that produced the most defects on the last project. Build an inspection plan for those, use it consistently and only then extend it.
Sources and legal basis
The legal statements in this article are based on the primary sources listed below. The article is not a substitute for legal advice in an individual case.
- Section 640 German Civil Code (BGB) — acceptance and the shift in the burden of proof
- Section 634 German Civil Code (BGB) — the client's rights in the event of defects: subsequent performance, self-remedy, price reduction, damages
- VOB/B (2016 edition), official text of the Federal Ministry for Housing, Urban Development and Building — Section 4 (7): removal of defective work during execution
- Annex 10 HOAI — basic services of site supervision, among them keeping a site diary
Find defects while they are still craftsmanship.
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