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Construction

The installer who arrives last

You arrive with the job finished, in a hurry, and sign over work you never saw done. That is where the risk sits.

Updated on 13/08/2026

You arrive last, when the job is running late and everyone is in a hurry. Much of what you have to connect is already done: closed ducts, executed penetrations, material installed by someone else. And what you are asked for at the end is a certificate with your name on it.

What gets signed and what people think gets signed

What people believeWhat it usually means
«I certify what I installed»The certificate usually covers the whole installation
«What came before is not mine»Connect to it and it becomes yours
«The design team already checked it»Their check does not replace yours
«It is a formality to finish»It is the document examined if something fails

Important

**What you cannot see, you cannot certify — and saying so in writing is the only thing that protects you.** If the duct was closed before you arrived, record it at the time, with a date: «section X could not be verified as it was already executed and closed». That sentence, written the day it happens, is the difference between certifying with reservations and certifying blind. Written afterwards, it is no longer worth the same.

What to do on arrival, hurry or no hurry

  1. 1

    Photograph what you find, dated

    Especially what you will connect to and did not build.

  2. 2

    Ask for documentation of what was executed before

    Material, markings and who installed it.

  3. 3

    Record what cannot be verified, at the time

    And put it in writing to whoever hired you.

  4. 4

    And hand over your documentation on finishing, not months later

    At handover everyone disappears, you included.

Watch out

The pressure typical of this position and how to hold it: **you will be asked to sign so the job can be handed over, and asked the same day**. A flat refusal breaks the commercial relationship; signing without reservations leaves you alone if something fails. The third way works: certify what you did verify and record, in the same document, what could not be checked and why. It is nearly always accepted, because whoever asks knows exactly what they are asking.

Worth knowing

What an installation certificate covers, who may issue one and what liability it carries depends on the installation type and the applicable rules. **Your adviser or professional body settles that before you sign**; here we explain how to reach that signature with what you did not see written down rather than remembered.

Can I certify only my part?

It depends on the installation. Ask BEFORE accepting the job, not at signing.

What if the duct was already closed?

Record it at the time and in writing. Later is not the same.

I am being pressed to sign today

Certify what was verified and write down what was not. It is usually accepted.

A real case

The situation

The duct was closed before arrival and the certificate is signed saying nothing.

What you do

  1. Records on the certificate which section could not be verified, and why

What you get

The signature covers what was checked, not what nobody saw.

The situation

You are asked to sign the same day so the job can be handed over.

What you do

  1. Certifies what was verified and records in writing what remains unchecked

What you get

The job is handed over without signing blind or breaking with the client.

The situation

Months later a fault appears in a section built by someone else.

What you do

  1. Photographs what is found on arrival, dated

What you get

The condition of what was connected to can be evidenced.

The situation

Installed material has no documentation and nobody knows who fitted it.

What you do

  1. Requests documentation of prior work before connecting

What you get

The installation is certified knowing what it is made of.

The situation

Their own documentation is handed over three months after completion.

What you do

  1. Hands over documentation on finishing, before everyone disappears

What you get

The project file closes with their part inside it.

The situation

A job is accepted without knowing whether only part of it can be certified.

What you do

  1. Asks the certificate's scope before accepting the commission

What you get

The scope is known while saying no is still possible.

This article answers

  • installer certificate liability
  • signing off an installation i did not do
  • documentation an installer hands over
  • asked to certify someone elses work