A carbon fibre strengthening evidence pack should prove what was installed, where it was installed, how it was tested and what future works must avoid. While CFRP plates and carbon fibre wrap may be thin and easy to conceal behind finishes, the evidence pack is what allows the client, engineer, contractor and future maintenance team to understand the strengthening system after the work has disappeared from view.
This is especially important on refurbishment projects, slab openings, beam strengthening, column wrapping and change-of-use works where the strengthened area may later be hidden by ceilings, services, fire protection, access panels or architectural finishes. Without a clear evidence pack, the project may have a completed CFRP installation but no reliable record of the design assumptions, substrate condition, pull-off results, resin controls or no-drill zones.
This article completes London Construction Magazine’s practical series on carbon fibre strengthening in existing concrete structures, where CFRP is treated as a designed, tested and evidenced structural intervention rather than a simple surface product.
Start With the Final Strengthening Record
The handover pack should start by identifying the structural element strengthened and the reason for the strengthening. It should show whether the work involved CFRP plates, carbon fibre wrap, slab soffit strengthening, beam strengthening, column confinement, slab opening reinforcement or local repair before alteration works.
The pack should include the latest design drawing or marked-up installation layout, with enough information to show the installed locations, plate lines, wrap areas, fibre direction, number of layers, termination zones and any areas where the design was changed after site inspection. If the CFRP is later covered, the record may become the only practical way to understand where the strengthening sits.
This is why photographs should not be treated as optional. The evidence pack should include clear images of the area before preparation, after preparation, during installation and after completion. Where possible, photographs should include location references, date records or drawing references so they remain useful after the site team has left.
Substrate Evidence Should Not Be Lost
CFRP strengthening depends on the concrete substrate, so the evidence pack should show how that substrate was checked and accepted. This may include existing drawings, investigation results, GPR or rebar scanning records, concrete strength information, opening-up photographs and notes on the exposed concrete condition.
If the design relied on a concrete class such as C30/37, C32/40 or C40/50, the handover information should make clear whether that assumption was based on drawings, investigation, testing or engineering assessment. The client does not need a pile of unexplained documents, but they do need a clear chain between design assumption and site evidence.
Surface preparation evidence is also important. Laitance removal, mechanical grinding, grit-blasting, coating removal, local repair, vacuum cleaning and substrate acceptance should be recorded. Where the specification required a prepared surface profile such as ICRI CSP 3 to CSP 5, the evidence pack should show how that requirement was checked or signed off.
| Evidence Pack Item | Why the Client Needs It |
|---|---|
| Design and layout records | Shows what element was strengthened, where the CFRP was installed and what structural action the system supports. |
| Substrate preparation photos | Proves that laitance, coatings, dust and weak material were removed before bonding. |
| Pull-off test records | Confirms whether the prepared concrete achieved the required tensile bond strength and records the failure mode. |
| Resin and environmental logs | Records batch numbers, expiry dates, temperature, humidity, dew point and curing conditions. |
| No-drill and maintenance information | Protects the strengthened zones from later drilling, cutting, chasing, impact damage or unreviewed alteration. |
Pull-Off Results Must Be Included Clearly
Pull-off testing records are one of the most important parts of a CFRP evidence pack. The client should receive the test locations, dolly size, curing period, test date, equipment details where relevant, failure load, calculated tensile bond strength and failure mode.
A typical minimum value used on many bonded CFRP strengthening projects is 1.5 N/mm², but the handover pack should not present this as a universal rule. It should refer back to the project specification, engineer’s design and selected CFRP system. The pack should also make clear whether the result was accepted, rejected, retested or reviewed by the responsible engineer.
Failure mode is essential. Concrete substrate failure, adhesive failure and interface failure do not mean the same thing. A clean record allows the client and design team to understand whether the substrate itself failed, whether the adhesive bond failed or whether the surface preparation may have affected the test. This is why the evidence pack should link directly back to the project’s CFRP strengthening ITP requirements, where pull-off testing, inspection points and final sign-off should already be controlled.
Resin, Curing and Environmental Records Matter
CFRP strengthening uses epoxy adhesives and resin systems, so the handover pack should include the product data, resin batch numbers, expiry dates, mixing records and installation dates. This helps show which materials were used and whether they were installed inside the required working and curing windows.
Environmental records should also be kept. The pack should include substrate temperature, ambient temperature, relative humidity and dew point readings taken before installation and, where required, during curing. For epoxy resin works, substrate temperature should normally be at least 3°C above dew point to reduce condensation risk, and the selected resin system may include minimum and maximum temperature limits that must be followed.
These records protect more than the installer. They help the client understand that the CFRP was not only applied to the correct location, but applied under conditions suitable for bonding and curing. This is especially important where the work took place in basements, cold slabs, damp structures, enclosed refurbishment areas or overhead soffit zones.
Final Restrictions Protect the Strengthening
A CFRP evidence pack should always include final restrictions. The client should be told that drilling, chasing, cutting, fixing, grinding or later penetrations through strengthened zones should not be carried out unless reviewed by the responsible engineer. The installed system may be thin, but it is part of the structural load path.
This becomes critical once the CFRP is hidden. A future trade may not know that a black plate or wrap sits behind a ceiling, above a service zone or around a structural opening. Without drawings, photographs and no-drill notes, the strengthened area can be damaged accidentally during later fit-out, maintenance or refurbishment works.
This is one of the most common long-term risks in CFRP works. London Construction Magazine’s article on common CFRP strengthening failures explains why future trade damage, missing records and poor handover controls can undermine an otherwise competent installation.
What Clients Should Keep for the Building Record
The final evidence pack should be retained as part of the building record. It should be useful not only on completion day, but also years later when the building is altered, maintained, sold, inspected or refurbished again. The pack should explain the CFRP system in plain enough terms for future teams to understand the restrictions without needing to reconstruct the full project history.
The strongest handover packs include design drawings, marked-up locations, photographs, ITP records, pull-off test sheets, resin batch records, environmental logs, inspection sign-offs, defect records, repair records, maintenance notes and no-drill zones. If fire protection, impact protection, coatings or access restrictions apply, these should also be recorded.
For clients, the benefit is simple: the structure remains understandable. CFRP strengthening should not become invisible risk. A good evidence pack turns a hidden structural intervention into a recorded asset that can be managed, protected and inspected over time.
Handover Reading
A carbon fibre strengthening evidence pack should show what was designed, what was found on site, how the concrete was prepared, whether the bond was proven, which materials were used, what conditions existed during installation and what restrictions apply after handover. The strongest CFRP projects do not end when the plate or wrap cures. They end when the client receives a clear record that protects the strengthened element from being misunderstood, damaged or forgotten.
Client Questions on CFRP Handover Evidence
What should a CFRP evidence pack include?
It should include design records, marked-up locations, preparation photos, pull-off test results, ITP records, resin batch numbers, environmental checks, installation photographs, final sign-off and no-drill restrictions.
Why do clients need CFRP photographs at handover?
Photographs help prove where the CFRP was installed and what condition the substrate and finished system were in before the strengthening is hidden by finishes or services.
Should no-drill zones be included in the handover pack?
Yes. No-drill and no-cut zones should be clearly recorded so future trades do not damage CFRP plates or wrap without engineer review.
How long should CFRP handover evidence be kept?
CFRP handover evidence should be retained with the building record for as long as the strengthened element remains in service, especially where future refurbishment or intrusive works may occur.
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Expert Verification & Authorship: Mihai Chelmus
Founder, London Construction Magazine | Construction Testing & Investigation Specialist |
