Note
What Happens to a Subcontractor's Work at Handover
On most C&I solar and factory LED projects in Thailand, the main contractor does not do all the work. A roofing company prepares the mounting structure. A civil contractor lays the cable trench. A scaffolding company handles the lift for a high-bay LED installation. The main contractor’s technicians do the electrical installation itself. But when the factory’s engineer picks up a pen to sign the handover document, there is one signature at the bottom: the main contractor’s. That signature covers all of it, including the work the main contractor’s crew never touched.
What Does “Covering All of It” Actually Mean?
The factory signed a contract with the main contractor. From the customer’s point of view, the main contractor is responsible for the complete installation, regardless of who physically did each part. If the roof mount fails eighteen months after handover and water enters the factory ceiling, the factory calls the main contractor. If the civil work undermines a cable run, the factory calls the main contractor.
This is not unusual. It is how construction contracts work. The main contractor’s obligation is to deliver a complete, functioning installation. Which subcontractors they use to deliver it is their business decision, not the customer’s problem.
The difficulty is not the legal structure. The problem is that most main contractors do not document the subcontractor’s work in a way that lets them do anything useful with that responsibility later.
What Does a Subcontractor Actually Leave Behind?
When a subcontractor finishes their part of a factory installation, they typically submit their invoice to the main contractor and leave for the next job. What they rarely leave behind is documentation the main contractor can actually use: a formal scope of work, a list of installed materials with model numbers and warranty periods, or a contact that will still work in two years.
The main contractor accepts the work, pays the invoice, and moves on. The materials the sub used, the verbal warranty from the site visit, the contact for warranty claims: these end up in an email thread or a project folder labeled in a way that is impossible to search when something fails eighteen months later.
What gets captured in the close-out record is usually only what the main contractor’s own crew installed: the inverters, the panels, the wiring, the DB connections. The roofing sub’s mounting rails, the civil sub’s conduit runs, the scaffolding company’s lift record: none of it appears, because the close-out workflow was built around the main contractor’s own scope.
The Gap That Shows Up at Inspection Time
A site register exists to answer one question on any future visit: what is installed here, who is responsible for it, and when does the coverage run out.
For the main contractor’s own work, this is usually documented. Panel specification, inverter brand, manufacturer warranty period: these come from procurement records and end up in the close-out file, in the same item-by-item installation record a signed handover depends on.
For the subcontractor’s work, the entry is typically blank or missing entirely. Two years after handover, when the annual electrical inspection is due, the inspection team goes to site with whatever register was built at close-out. They check the inverters and the panels. They do not check the roof mounting system because it is not on their list. They have no list of who warranted it or for how long.
When a leak appears six months later and the factory asks who is responsible for the waterproofing, the answer requires hunting through old invoices and hoping the subcontractor’s number still works. None of that is necessary if the record was built at the time.
What a Complete Record Actually Looks Like
The site register should cover the subcontractor’s work the same way it covers the main contractor’s own installation:
- Who did it: subcontractor name and a working contact number
- What they installed: materials, brand if known, specification, quantity
- When they completed it: the date the work was done
- What warranty they gave: period, what it covers, and any exclusions
- Who the warranty runs to: whether the sub warranted to the main contractor or directly to the factory
For most subcontracts on factory electrical projects, this is a few lines in the site record, not a separate document. A roofing subcontractor’s entry might read: ABC Roofing, 40 metres of aluminium mounting rails and 12 roof penetrations with EPDM sealing, completed March 2026, five-year waterproofing warranty to the main contractor, contact 081-XXX-XXXX.
That entry answers every question a future inspection or warranty claim will raise, and it takes five minutes to create while the information is still fresh.
A Worked Example
A 300kWp rooftop installation at a factory in Chonburi. Three parties do work on site:
- Main contractor’s crew: 1,200 panels, 4 inverters, AC cabling, DB connections, commissioning
- Roofing subcontractor: steel mounting rails, roof penetrations, EPDM waterproofing with a five-year warranty from the sub to the main contractor
- Civil subcontractor: cable trench from roof to main DB, 80 metres in conduit, sole trader with no formal warranty documentation
At handover, the factory signs one document with the main contractor. The site register should capture all three scopes.
For the civil sub, where no formal warranty paperwork exists, a name, phone number, scope, and date is still better than a blank entry.
Three years later, a conduit run is damaged during factory floor modifications. The factory asks the main contractor who is responsible. The main contractor opens the register: civil sub, 80 metres conduit, completed [date], contact [number]. That question is answered in under a minute. Without the entry, it cannot be answered from memory and someone has to start calling around.
FAQ
Does the subcontractor need to sign the main contractor’s handover document?
No. The handover document is between the main contractor and the factory. The subcontractor’s job is to give the main contractor enough information to represent their work accurately in the site record. The main contractor then incorporates that into the close-out package before the factory signs.
What if the subcontractor will not provide any documentation?
Build the requirement into the subcontract agreement before work starts. If the sub’s contract says they provide a material list and warranty confirmation at completion, they will. If it does not, most will not. The time to negotiate this is before mobilization, not after the factory has signed the handover.
What about sole traders and informal subcontractors?
Capture what is available: name, contact number, scope of work, completion date, and any verbal warranty they described on site. An informal note beats a blank entry. The liability may still fall back to the main contractor if something fails, but a basic record at least shows what was agreed and who to contact.
If your current close-out process has no structured place to record subcontracted work separately from your own installation, the TRACE 30 program page describes how the site register is built from closed jobs and what it captures. If you want to talk through how this applies to projects where you use roofing, civil, or other specialized subcontractors, you can schedule a call.