A practical, evidence-based screening framework for factories, warehouses and logistics facilities before final PV structural and mounting design.
Commercial rooftop solar structural due diligence is the first decision gate for a factory, warehouse or logistics facility. It classifies a project as ready for a preliminary quotation, needing more evidence, requiring a site survey and engineering review, or paused for roof repair or replacement. The purpose is to organize evidence before a supplier issues a final fixing layout or a load-related proposal within engineer-approved project limits.
Rooftop PV in Southeast Asia is a long-term infrastructure decision, not only an equipment purchase. Roof age, waterproofing, structural load paths, wind exposure, corrosion, drainage, fire access and local requirements all influence whether a project can proceed. A mounting supplier can support a concept design within verified limits, but it cannot certify the building itself.
What this due diligence covers
It covers
- Ownership, lease and roof-life screening
- Roof condition, waterproofing and drainage
- Structural load paths and existing alterations
- PV layout, access and cable-route constraints
- Required documents and responsibility boundaries
- A four-level project decision model
It does not cover
- Step-by-step installation instructions
- Universal roof-load or wind-speed values
- Generic screw spacing or rail-span advice
- Country-specific legal opinions
- Final structural approval or certification
- A substitute for a local engineer or roof specialist
Ziyuan Energy may prepare a preliminary mounting concept and bill of materials from information supplied and verified by responsible project parties. Building capacity, roof compatibility, waterproofing acceptance and regulatory compliance must be determined by the competent parties for the project.
The early go or no-go screen
Before detailed calculations or layout optimization, confirm whether the project is commercially viable and whether the building can be investigated without disrupting operations. This evidence-first gate is consistent with the project-development logic described in the Asian Development Bank’s Rooftop Solar Development Handbook; it is a planning reference, not a substitute for the applicable local code or engineer’s assessment.
| Screen | Questions to answer | Why it matters |
|---|---|---|
| Ownership and lease | Who controls the roof? Does the lease permit PV, penetrations, repairs and future access? | A short or uncertain tenure can make a long-life PV asset commercially unsuitable. |
| Roof age and service life | When was the roof built? What repairs or reroofing have occurred? Is its remaining life compatible with the project plan? | Roof replacement may require PV removal and reinstallation. |
| Warranty restrictions | What do the roof manufacturer and contractor say about clamps, penetrations and additional equipment? | Incompatible fixing details can restrict or void warranty coverage. |
| Operations and shutdown | Can the facility accept surveys, lifting, strengthening work, dust, noise or temporary exclusion zones? | Production and safety constraints affect the design and construction sequence. |
Roof condition and waterproofing review
The roof sheet and its waterproofing system form the physical interface between the PV array and the building. Review this interface before selecting a clamp, rail or fixing method.
| Item | What should be checked | Why it matters | Who verifies |
|---|---|---|---|
| Roof profile and system | Trapezoidal, corrugated, concealed-fix standing seam or concrete; manufacturer and system where available. | The profile determines compatible attachment methods and exclusion zones. | Roof contractor, EPC, roof manufacturer |
| Corrosion and repairs | Rust, coating loss, pitting, fatigue, patch repairs, damaged fixings and previous leaks. | Degraded sheets or fixings may not transfer PV forces safely to the frame. | EPC site team, roof specialist, engineer |
| Existing equipment | Skylights, vents, HVAC, safety anchors, signage and other penetrations. | These features constrain layout, waterproofing and cable routing. | EPC, roof contractor |
| Drainage | Gutters, downpipes, overflow routes, ponding and water paths around proposed arrays. | PV framing or cable trays must not create dams or obstruct drainage. | Roof designer, EPC, engineer |
Where the roof system has manufacturer-specific warranty rules, obtain the original manual and written clarification. Do not assume that a fixing method suitable for one metal profile is suitable for another.
Technical reference: For insurer-oriented roof-PV risk guidance, see FM Global Data Sheet 1-15. Roof-specific fixing and warranty decisions remain subject to the roof manufacturer’s current documents.
Structural load path review
Structural due diligence looks beyond the roof skin to the members that carry PV forces into the building frame and foundation. A typical load path may include modules, clamps, rails or brackets, roof sheets, purlins, trusses, beams, columns and foundations. The actual path must be confirmed from drawings and site evidence.
- Confirm purlin and rafter types, spacing, spans and connection details.
- Record existing equipment and historic alterations that consume structural reserve.
- Compare available drawings with the roof as built; do not rely on drawings that cannot be reconciled with site conditions.
- Ask the local structural engineer to determine the applicable load combinations and connection checks.
- Do not use the mounting supplier’s component calculation as proof of building-level capacity.
PV and construction loads
Project screening should identify, at minimum, permanent equipment loads, wind uplift and lateral actions, maintenance actions, and temporary construction loads. The relevant values depend on the building, location, roof geometry, exposure, equipment and national code. Generic figures from another project must not be treated as design values.
Wind effects are especially sensitive to roof edges, corners, array geometry, tilt, gaps and surrounding buildings. The roof sheet, attachment, purlin and frame all need a compatible design path. During construction, pallets, tools and workers can create temporary concentrated loads; the EPC should define safe staging and access areas.
Layout constraints
Drainage and roof equipment
Keep gutters, downpipes, valleys, overflow routes, vents and maintenance zones accessible. Coordinate cable trays and penetrations with the roof design.
Fire and maintenance access
Check the applicable local fire, safety and insurer requirements for access paths, equipment clearances and emergency operations. Do not assume one regional aisle rule.
Electrical coordination
Use the electrical single-line concept, inverter locations and cable routes to avoid clashes with structural and waterproofing details.
Future access
Reserve routes for inspection, roof repair, equipment replacement and safe fall-protection arrangements.
Documents required before final mounting-system design
A preliminary concept can be prepared from limited information. A final mounting-system configuration within the supplier’s scope requires a verified document set and remains subject to the project engineer’s approval, roof-system conditions and applicable permits.
| Document | Why it is needed | Prepared or verified by | Risk if missing |
|---|---|---|---|
| As-built structural drawings | Shows framing, member sizes and connections. | Owner’s engineer or original designer | Load paths and attachment zones cannot be confirmed. |
| Structural capacity assessment and approved design actions | Defines permissible additional actions, relevant load combinations and roof-interface or connection constraints under applicable codes. | Licensed structural engineer in the project country | No safe envelope for final spans, spacing, attachment density or interface forces. |
| Roof manuals and warranty documents | Defines compatible clamps, penetrations and maintenance conditions. | Roof manufacturer or contractor | Fixings may conflict with roof performance or warranty. |
| Written roof-manufacturer approval or interface detail, where required | Confirms that the proposed clamp or penetration detail is acceptable for the identified roof system. | Roof manufacturer or authorized roof contractor | A manual alone may not confirm project-specific warranty acceptance. |
| Roof condition survey | Records corrosion, leaks, repairs and drainage. | EPC site team and roof specialist | Deterioration may be hidden until construction or extreme weather. |
| Roof plan and equipment layout | Shows geometry, access, obstructions and no-go zones. | EPC or owner’s consultant | Arrays may conflict with drainage, access or existing equipment. |
| Module datasheet and electrical concept | Provides dimensions, weight, fixing zones and cable/inverter constraints. | Module supplier and electrical designer | Mechanical and electrical layouts may not align. |
| Local policy and permit summary | Confirms the applicable rooftop PV programme and approvals. | EPC and permit adviser | A technically viable project may not be approvable or connectable. |
| Engineer-approved interface reaction schedule, where applicable | Provides the mounting designer with approved local forces, reactions or boundary conditions without asking the supplier to infer building capacity. | Licensed structural engineer and EPC | The supplier may otherwise design from assumptions that are not approved for the building. |
Responsibility matrix
The mounting supplier designs its own hardware within specified forces and verified interface conditions. Its final mounting-system configuration remains subject to the licensed structural engineer’s approval, roof-manufacturer conditions and applicable permits. It does not certify the building or interpret the roof warranty on behalf of the manufacturer.
| Task | Owner | Roof party | Structural engineer | EPC | Mounting supplier |
|---|---|---|---|---|---|
| Roof history and condition records | R/A | C | I | R | I |
| Warranty and fixing restrictions | A | R/A | C | R | C |
| Building structural capacity | A | C | R/A | C | I |
| Design loads and code parameters | C | I | R/A | C | I |
| Overall PV layout coordination | C | I | C | R/A | C |
| Mounting configuration and BOM | I | C | C | C | R/A |
| Waterproofing execution | A | R/A | C | R | Follows approved interface details |
| Final building structural approval | A | I | R/A | Coordinates | I |
| Testing and handover records | A | I | C | R/A | C |
R = responsible for execution; A = accountable for the decision or approval; C = consulted; I = informed. The exact contractual allocation must be checked for each project.
Documentation reference: For PV documentation, verification and handover context, see IEC 62446-1. The project team must still apply the edition and additional requirements adopted by the responsible authority.
Four-level project outcome model
| Outcome | Entry conditions | Recommended next steps |
|---|---|---|
| Ready for preliminary quotation | Basic roof, site and component information is available and no obvious major damage or commercial conflict is known. | Prepare a non-binding concept and budgetary quote, clearly subject to engineering and regulatory review. |
| More documents required | Owner interest is confirmed, but drawings, warranties, survey records or policy information are missing. | Freeze detailed design and issue a formal document-request checklist. |
| Site survey and engineering review required | Corrosion, uncertain roof age, unclear framing, historic upgrades or other red flags are present. | Commission a local site survey and written engineering review before ordering hardware. |
| Pause, repair or replace roof | The roof or structure cannot safely support the proposed system or waterproofing risk is unacceptable. | Complete repair, replacement or strengthening, then restart the screening with updated evidence. |
Country context in Southeast Asia
Southeast Asia is not governed by one structural or rooftop-solar rule. The following context is directional only. Confirm the current programme, permit pathway and national code through the responsible official authority and local professionals before design or publication claims are finalized.
- Philippines: Check the applicable Department of Energy rooftop-solar pathway and the current National Structural Code requirements. A Lingayen Municipal Hall public tender illustrates how one Philippine project can require roof stability studies and code-based design; its requirements do not become a universal rule for every roof.
- Malaysia: Check current Suruhanjaya Tenaga self-consumption guidance and applicable Malaysian structural and wind-loading standards. Programme requirements and technical studies can vary by project scope.
- Thailand: Check current Energy Regulatory Commission guidance and the relevant MEA or PEA connection requirements. Administrative pathways do not remove the need to check wind actions, roof capacity and safety with a Thai professional.
- Indonesia: Check current rooftop-PV policy and quota or approval information through the Ministry of Energy and Mineral Resources and the applicable Indonesian structural standards. Existing industrial roofs require project-specific review before a mounting configuration is committed.
- Vietnam: Check the current self-production/self-consumption framework through the Ministry of Industry and Trade and the applicable Vietnamese construction, fire and structural requirements. Policy names and editions must be confirmed before publication.
Country-source note: The links above are official authority portals, not a substitute for the current project-specific regulation, permit or engineering review. Use the exact current document edition applicable to the project.
What can prevent final mounting design approval?
| Potential blocker | Evidence needed | Why design cannot proceed | Who must act |
|---|---|---|---|
| No as-built structural drawings | Verified drawings or a measured structural survey | Load paths and member capacities cannot be confirmed. | Owner, structural engineer |
| No signed capacity assessment | Formal report under applicable local codes | There is no safe envelope for mounting design. | Owner, structural engineer |
| Unclear roof warranty | Manufacturer documents and written clarification | Fixings may conflict with the roof system or warranty. | Owner, roof party |
| Severe corrosion or leakage | Roof inspection report with photographs and condition grading | Sheets and fixings may not transfer forces or maintain waterproofing. | Owner, roof party, engineer |
| Unresolved material compatibility | Mounting specification and roof interface details | Incompatible metals may create corrosion risk. | EPC, mounting supplier |
| Drainage or access conflict | Coordinated roof layout | PV may obstruct water paths or required access. | EPC, safety professionals |
| No local engineer sign-off | Signed project-specific structural assessment | Building-level adequacy remains unverified. | Owner, structural engineer |
Frequently asked questions
How can we quickly screen a factory roof for PV?
Check ownership, lease rights, roof age, warranty conditions, visible damage, existing equipment, drainage and basic project-policy fit. This only determines the next investigation step; it does not approve the roof.
What does a mounting supplier need before issuing a final fixing layout?
Typically, verified structural drawings or a survey, a project-specific capacity assessment with approved design actions where applicable, roof manuals and warranty documents, written roof-interface approval where required, roof-condition evidence, the module datasheet, roof layout and the electrical concept.
Can generic wind or dead-load figures from another project be reused?
No. Design actions depend on location, exposure, roof geometry, equipment and the applicable national standards. They must be determined for the project.
What if the planned fixing method conflicts with the roof warranty?
Ask the roof manufacturer or responsible roof contractor to confirm an approved interface. Adapt the mounting method or pause the project if the warranty and waterproofing requirements cannot be reconciled.
Does a lighter PV system remove the need for structural checks?
No. Weight is only one part of the assessment. Wind actions, connections, corrosion, drainage and existing structural condition still require review.
Can a mounting supplier certify that a building is structurally safe?
No. The supplier can design its own mounting components for specified forces. Building-level capacity and code compliance must be assessed and approved by the responsible local professionals.
When should a project pause for roof repair or replacement?
Pause when the roof or supporting structure cannot safely carry the proposed actions, when waterproofing risk is unacceptable, or when required evidence cannot be verified.
How should disagreements between the EPC and supplier be resolved?
Use the project-specific structural engineer’s code-based assessment, obtain the roof party’s warranty interpretation, and request an alternative mounting configuration that respects both.
Prepare a better preliminary review
For an initial mounting review, prepare roof photographs, roof-profile information, building location, roof plan, structural drawings if available, module datasheets, target capacity and any roof warranty documents. Ziyuan Energy can use verified project information to prepare a preliminary mounting concept for review by the responsible project professionals.
Related technical resources
- Commercial trapezoidal and metal-roof mounting guide
- Standing seam installation guide
- Solar mounting materials comparison
- Solar carport selection guide
- Grounding and bonding guide
Sources and technical references
- Asian Development Bank, Rooftop Solar Development Handbook. Referenced for independent technical and structural review in project due diligence.
- FM Global Data Sheet 1-15, Roof Mounted Solar Photovoltaic Panels. Referenced for insurer-oriented roof-PV hazards, access and natural events.
- IEC 62446-1. Referenced for PV system documentation, testing and handover context.
- Lingayen Municipal Hall public bidding document. A project-specific Philippine example, not a regional rule.
- For current country requirements, begin with the official authority portals linked in the country-context section and confirm the exact national code, programme, permit and edition applicable to the project.
Technical note: Source references provide context and do not replace project-specific engineering, roof-manufacturer instructions, local permits or professional approval.
