Agreeing tolerances before the work starts
The floor finish contractor checks a completed slab and says it is outside the required flatness. The concrete foreman says nobody told the crew that the finish needed a different result. Each trade brought a different way of measuring it.
Find the project's measurable limits and agree how, where and when they will be checked before the work starts. Bring the producing trade and the following trade into that discussion. Tolerance arguments often combine an unclear requirement with different measurement methods. An agreed method makes the result comparable; it does not give the site team authority to relax the specification.
- Read the relevant specification sections and referenced requirements for both the work and the next installation. Record the applicable limit and document revision without copying a number from another job.
- Ask the responsible designer to resolve gaps or conflicting requirements. Identify which result the producing trade must achieve and which substrate condition the following trade needs.
- Agree the measurement method, instruments, reference points and timing with the responsible reviewer. State how the sampled locations are chosen so neither side selects only convenient spots.
- Brief the foreman before production. Use a marked detail or a small trial area to explain the requirement and the evidence expected at the check.
- Check the first suitable area together and record the result. If the method exposes a problem, resolve it before the same work continues across the whole floor.
- Keep the agreed measurement record and any authorized clarification with the inspection plan. Rebrief replacement supervisors and affected trades when the requirement or installation sequence changes.
Common mistakes
- Assuming every referenced standard uses the same measuring method.
- Agreeing the limit but leaving the inspection timing unspecified.
- Letting the follow-on trade introduce an undocumented stricter criterion at handover.
- Treating a visually acceptable sample as proof that a numeric requirement was met.
Checklist
Before the crew begins
- Applicable requirement and revision
- Follow-on installation needs understood
- Measurement method and timing
- Locations and reference points agreed
- Foreman briefed
- First result and clarifications recorded
Check your understanding
Two trades agree on a limit but their instruments produce different results. What should you resolve first?
Show the answer
Confirm the specified measurement method, reference points and conditions with the responsible reviewer. Comparing results from different methods may not answer the requirement at all. Use the agreed method to establish the record before discussing whether correction is needed.
