---
id: KB-CN-019
url: https://app.codecontract.io/help/construction/the-installer-who-arrives-last
idioma: en
categoria: sector-construccion
subcategoria: noresidencial
audiencia: usuario
nivel: intermedio
actualizado: 2026-08-13
tambienEn: [es]
relacionados: [KB-CN-018, KB-CS-017, KB-CN-007]
citadoPor: [KB-CN-021, KB-CN-023, KB-CN-029]
---

# 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._

**Responde a:** installer certificate liability · signing off an installation i did not do · documentation an installer hands over · asked to certify someone elses work

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 believe | What 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. **Photograph what you find, dated** — Especially what you will connect to and did not build.
2. **Ask for documentation of what was executed before** — Material, markings and who installed it.
3. **Record what cannot be verified, at the time** — And put it in writing to whoever hired you.
4. **And hand over your documentation on finishing, not months later** — At handover everyone disappears, you included.

> [!WARNING]
> 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.

> [!NOTE]
> 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.

## Ejemplos

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

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

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

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

- Certifies what was verified and records in writing what remains unchecked

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

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

- Photographs what is found on arrival, dated

→ The condition of what was connected to can be evidenced.

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

- Requests documentation of prior work before connecting

→ The installation is certified knowing what it is made of.

**Their own documentation is handed over three months after completion.**

- Hands over documentation on finishing, before everyone disappears

→ The project file closes with their part inside it.

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

- Asks the certificate's scope before accepting the commission

→ The scope is known while saying no is still possible.