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Snagging is the process of identifying visible defects, incomplete work and items that need correction before or around project handover. On a commercial roof project, that can include waterproofing details, gutters, outlets, rooflights, penetrations, coatings, fixings, access equipment, debris and other visible workmanship issues.
For a building owner or facilities manager, the objective is not to prove that the roof has no defects whatsoever. Some defects are latent, meaning they are hidden and may only become apparent later. A snagging inspection is therefore a structured acceptance check, not a guarantee that every concealed issue has been found.
This guide explains what to check, how to record defects and when to pause project acceptance. It is focused on the physical roof and visible completion standard. Document handover, warranties and the CDM health and safety file are separate close-out tasks and should be checked alongside, not confused with, the snagging process.
This checklist does not replace the contract administrator, project manager, surveyor or other professional responsible for certifying practical completion. The legal and contractual test for practical completion depends on the contract and the judgement of the relevant certifier.
It also does not detect every latent defect. RICS distinguishes patent defects, which are obvious or discoverable, from latent defects that remain hidden and appear later. A roof can therefore pass a careful visual snagging inspection and still develop a concealed defect afterwards.
The purpose of snagging is to make visible completion issues difficult to miss and easy to close out. Where hidden condition, structural integrity or system performance is uncertain, further investigation may be needed.
Pause the inspection if safe roof access has not been established. HSE guidance says roofs should be treated as fragile until a competent person confirms otherwise, and effective precautions are required when working on or near fragile surfaces. A facilities manager should not climb onto a roof simply to complete a snagging checklist if the access system and fall-risk controls are unclear.
Escalate before acceptance if there is active water ingress, open or incomplete waterproofing, unsafe rooflights, missing edge or access protection included in the contract, exposed structural defects, unsecured materials or incomplete work that could affect safe use of the roof or building below.
A commercial roof snagging inspection asks whether the completed visible work matches the agreed scope, is complete enough for its intended use and contains identifiable defects that should be corrected.
That means checking three things separately:
The snag list should not become an informal redesign exercise. If the client wants additional work that was not part of the original contract, record that separately from defects in the contracted work.
Before inspecting, gather the latest agreed drawings, specifications, approved variations and roof-zone information. If the project changed during construction, use the current information rather than the original tender drawing.
A snagging inspection is much stronger when each roof area can be checked against what was supposed to be installed. Without that baseline, the client may identify cosmetic preferences but miss a significant scope omission.
If the building owner needs an independent condition view rather than a contractor-led close-out inspection, a commercial roof condition inspection can provide a broader assessment of the completed or existing roof.
Check for obvious splits, punctures, poorly finished laps, lifted edges, incomplete seams, exposed fixings where they should be covered, loose sheet edges or other visible discontinuities. The exact detail depends on the roof system, so compare against the approved specification rather than applying one generic standard to every roof.
Inspect parapets, kerbs, abutments, perimeter trims and transitions between materials. Look for incomplete terminations, loose components, gaps, poorly sealed junctions or details that do not match the agreed drawing.
Where areas were damaged or changed during construction, confirm the repair has been completed and recorded. Temporary patches should not be accepted as permanent work unless that was the agreed final detail.
Penetrations are common snagging locations because they bring together waterproofing, services and structural details. Check pipework, ducts, vents, cable penetrations, plant supports and other openings against the agreed design.
Look for incomplete seals, poorly formed upstands, unsupported services, unsealed gaps, fixings through waterproofing that were not part of the design, or later contractor work that has damaged completed roof details.
If several trades have worked on the roof, establish responsibility for each defect rather than assuming every issue belongs to the roofing contractor. The snag list should still record the roof impact even where another trade must rectify it.
Drainage should be visually complete and free from construction debris at handover. Check gutters, sumps, outlets, overflows and downpipe connections that form part of the works.
Look for offcuts, packaging, sealant tubes, fasteners, insulation fragments or other debris that could obstruct drainage. Confirm that outlet guards, leaf guards or other specified components are fitted where required.
Where practical and safe, check whether visible falls and local details support drainage rather than creating obvious trapped-water points. Do not infer hydraulic performance from a brief visual inspection where a drainage design or test is required.
Check rooflights for visible damage, incomplete seals, poor interfaces with the surrounding roof and any protective systems included in the project. Where old rooflights or fragile areas remain, confirm that the handover information identifies them clearly.
Do not walk onto or near a rooflight to inspect it unless the safe system of work specifically allows that access. HSE identifies fragile surfaces as a serious roof-work risk and requires appropriate precautions.
The existing commercial roof access planning guide is useful where the project has changed the long-term access arrangement or where future FM access remains unclear.
On sheeted or mechanically fixed systems, inspect accessible areas for visibly missing, loose, poorly seated or inconsistent fixings. Check trims, flashings and other metalwork for sharp projections, incomplete fixings, damage or obvious distortion.
Do not use snagging as a substitute for technical pull-out testing or design verification where those are specified. The visual check is intended to identify obvious anomalies and incomplete work.
For coated or liquid-applied roofs, inspect the finished surface for obvious missed areas, contamination, damage, incomplete reinforcement details or irregular transitions around penetrations and edges.
Visual appearance alone does not prove required film thickness, adhesion or cure performance. Where the specification requires test results, wet-film records, dry-film measurements or other quality evidence, check those records separately as part of project close-out.
Where the project includes walkways, guardrails, anchors, fixed ladders, access hatches or other safety equipment, confirm that the visible installation is complete and that the associated handover information has been provided.
Check for incomplete sections, loose components, blocked access routes, missing labels or equipment positioned differently from the approved layout. Where testing, certification or specialist commissioning is required, do not treat a visual check as a substitute for that evidence.
A completed commercial roof should not be left with construction waste, redundant materials or loose items that can block drainage, damage the membrane or create a windborne hazard.
Check that offcuts, fixings, packaging, temporary protection and unused materials have been removed unless there is a clear reason for approved spare materials to remain. If spare materials are left for future repairs, they should be stored appropriately rather than abandoned on the roof.
A snag list should be specific enough that another person can find the issue, understand it and confirm when it has been corrected.
This structure prevents common problems such as “repair flashing” with no location, photograph or agreed completion evidence.
Pause close-out if the inspection identifies an issue that could compromise immediate weatherproofing, safe access or the agreed functional use of the roof. Minor cosmetic items can be prioritised differently, but the classification should be explicit.
A snag is an incomplete or defective part of the contracted work. A maintenance item is an action expected during the normal life of the roof. Mixing the two can shift responsibility unfairly or make genuine defects look like routine FM tasks.
For example, construction debris left in a gutter is a handover issue. Future periodic gutter cleaning is a maintenance task. A missing seal at a penetration is a defect. Inspecting that seal as part of a future planned maintenance visit is an FM responsibility after the work has been accepted.
The site’s planned industrial roof maintenance service provides the longer-term route once handover defects have been closed and the roof moves into normal operation.
The snag list should feed into the project’s contractual defect process. RICS guidance explains that minor patent defects may be recorded on snagging or defect lists around practical completion, but the treatment of defects and completion depends on the contract.
The client should therefore avoid inventing a separate informal process that conflicts with the contract administrator’s role. Agree who issues the snag list, who accepts close-out evidence and how outstanding items are tracked after practical completion.
If a significant defect calls the broader repair strategy into question rather than simply requiring correction of new work, the existing commercial roof repair-or-replacement decision guide provides a separate framework for assessing the wider intervention.
Inspecting only from ground level. Ground-level photographs can miss important roof details. Use a safe, planned inspection appropriate to the roof.
Treating photographs as the snag list. Photographs without location, description and responsibility are difficult to manage.
Accepting temporary repairs as permanent work. Confirm whether a patch or temporary protection is part of the approved final detail.
Ignoring work by other trades. Plant installers, electricians, or other contractors may have damaged completed roofing. Record the roof defect even if responsibility lies elsewhere.
Using snagging to demand extra work. Keep genuine contract defects separate from new client requests or enhancements.
Assuming no visible defect means no hidden defect. Snagging is strongest at identifying patent defects. It cannot prove there are no latent defects.
Closing snags without evidence. Record completion photographs or reinspection notes rather than relying on verbal confirmation.
After the first inspection, issue one controlled snag list rather than several competing versions. Give every item an owner and status. When rectification is reported complete, verify the item in a way proportionate to its importance.
High-priority weatherproofing or safety items may justify physical reinspection. Minor cosmetic items may be closed through clear photographic evidence if the project team accepts that method.
Do not delete closed items from the record. Mark them complete with the date and evidence. This creates a simple audit trail and makes it easier to see which issues remain outstanding.
Once the snag list is closed, retain the final inspection record with the roof handover information. The photographs and roof-zone references can provide a useful baseline for later inspection.
If a future leak or defect appears, the FM team can compare the condition with the accepted handover state rather than starting with no record of how the roof looked when the project finished.
Plan the snagging inspection before the contractor demobilises. Agree who will attend, which drawings and specifications will be used, how safe access will be managed and who has authority to classify and close items.
Walk the roof systematically by zone rather than following defects randomly. Check the covering, drainage, penetrations, rooflights, edges, access systems and housekeeping in each area before moving on.
Issue one numbered snag list with photographs and target dates. Separate urgent weatherproofing or safety issues from minor cosmetic items and from future maintenance requirements. Reinspect important defects after rectification and retain the final closed list with the project handover records.
If the building owner wants an independent roof-condition check before or after accepting the works, send the project details to Industrial Roofing Services to discuss the appropriate survey or inspection.
Commercial roof snagging is a structured acceptance check for visible defects, incomplete work and outstanding items. It should be based on the agreed roof scope, carried out using safe access and recorded in enough detail for every issue to be found and closed.
The strongest checklist covers waterproofing, seams, flashings, penetrations, drainage, rooflights, fixings, coatings, access systems, safety equipment and housekeeping. Each snag should have a unique ID, location, description, photograph, responsible party and close-out status.
Snagging does not prove that the roof has no latent defects, and it does not replace the contractual practical-completion or defects process. Its value is in making visible problems explicit before they are forgotten, disputed or passed into routine FM responsibility.
Roof snagging is the process of identifying visible defects, incomplete work and outstanding items around project completion so they can be recorded and corrected.
No. Snagging checks completed work against the agreed project scope. A roof survey can have a broader purpose, such as assessing condition, defects, remaining life or repair requirements.
Yes. Snagging is mainly effective at identifying patent defects that are visible or discoverable at the time. Latent defects can remain hidden and become apparent later.
That depends on the contract and project team. It may be prepared by the contract administrator, surveyor, clerk of works, project manager or another person acting for the client. The process should align with the contract.
Not necessarily. RICS guidance notes that minor items may be dealt with through snagging or defects lists around practical completion. The actual decision depends on the contract and the judgement of the relevant certifier.
Yes, where they form part of the project. Check that drainage components are complete, connected and free from construction debris, while recognising that hydraulic performance may require separate design or testing evidence.
Warranty documents belong in the wider handover process rather than the physical snagging list. The snagging inspection should focus on visible defects and incomplete work.
