Structural investigations should be planned around the engineering decision that the project needs to make. The investigation may need to confirm construction details, material properties, reinforcement, structural condition, connections, foundation arrangements or the cause of visible defects.
The strongest investigations begin with a clear brief, a review of available records and a staged strategy that uses non-destructive methods before targeted intrusive work. Locations, quantities, opening sizes, tests, access requirements, reinstatement and reporting outputs should be agreed before the site team mobilises.
Poorly planned investigations can create unnecessary damage while still failing to collect the evidence required by the structural engineer. A request to “scan the slab” or “open the wall and see what is there” is rarely detailed enough to control the technical work, site risks or final deliverables.
The key point is this: structural investigation planning should work backwards from the decision that must be supported. Every scan, breakout, core, trial pit or sample should have a defined purpose, location, method, output and review route.

What Is the First Step in Planning a Structural Investigation?

The first step is to define the engineering question. The investigation should not begin by selecting equipment or deciding how many holes to form.
The project team should first identify what must be known and what decision will be made using the results.
Examples include:
  • Can an existing floor support new plant?
  • Can a new opening be formed through a concrete slab?
  • What reinforcement is present around a proposed penetration?
  • How is an existing steel beam connected?
  • Is a masonry wall loadbearing?
  • What is the construction and thickness of an existing slab?
  • What caused cracking or movement?
  • What foundation type and dimensions are present?
  • What material properties should be used in a structural assessment?
  • How is an existing façade bracket connected to the primary structure?
A clear question allows the structural engineer to identify the minimum evidence required and select methods that are proportionate to the decision.

Why the Engineering Decision Must Be Defined

The same structural element may require very different investigations depending on the proposed work.
Proposed Decision Information Potentially Required Possible Investigation Methods
Install several shallow anchors Shallow reinforcement, tendons, services, concrete condition and fixing zone. Scanning, drawings and local substrate checks.
Form a large slab opening Slab thickness, top and bottom reinforcement, tendons, support zones and load paths. GPR, cover survey, breakouts, cores, drawings and structural analysis.
Install heavy plant Structural system, member sizes, reinforcement, material strength and existing condition. Dimensional survey, scanning, cores, connection exposure and calculations.
Investigate cracking Crack pattern, movement, reinforcement, material condition, loading and environmental history. Visual mapping, monitoring, scanning, opening-up and material testing.
Plan demolition Structural system, continuity, connections, prestressing, stability and concealed alterations. Document review, opening-up, scanning, surveys and temporary works assessment.
Without the proposed decision, the investigation contractor may collect technically correct information that is not sufficient for the engineer’s assessment.

Who Should Prepare the Investigation Brief?

The structural engineer or designer responsible for the assessment should normally define or approve the technical investigation brief.
The brief may be developed with input from:
  • The client or building owner.
  • The principal designer.
  • The principal contractor.
  • The temporary works designer.
  • The demolition engineer.
  • The façade engineer.
  • The materials specialist.
  • The structural investigation contractor.
  • The building operator.
  • The laboratory.
The investigation contractor can advise on access, equipment, practical methods and likely limitations. However, the responsible engineer should determine what information is necessary for the engineering decision.

What Should the Investigation Brief State?

  • The purpose of the investigation.
  • The proposed alteration, load or assessment.
  • The building, level, grid and structural element.
  • The exact information required.
  • The investigation methods.
  • The number and distribution of locations.
  • The permitted opening or sample dimensions.
  • Required depths and orientations.
  • Acceptable alternative positions.
  • Required site and laboratory measurements.
  • Photographic and drawing requirements.
  • Reinstatement responsibility.
  • The report format.
  • The review and approval route.
The brief should be detailed enough for the work to be priced and delivered consistently without requiring operatives to make structural decisions on site.

How Does the Desk Study Support Investigation Planning?

The desk study reviews available information before site methods and locations are finalised.
Relevant documents may include:
  • Original structural drawings.
  • Reinforcement drawings and schedules.
  • Post-tensioning layouts and stressing records.
  • Architectural drawings.
  • Mechanical and electrical service drawings.
  • Specifications.
  • As-built information.
  • Previous structural reports.
  • Historic investigation reports.
  • Repair records.
  • Alteration drawings.
  • Fire-strategy and façade information.
  • Hazardous-material surveys.
  • Operation and maintenance records.
The purpose is not only to collect drawings. It is to identify what is known, what is uncertain and where records conflict.

How Reliable Are Existing Drawings?

Existing drawings should be classified according to their likely reliability.
Drawing Type What It May Represent Planning Implication
Design drawing Original design intent. Critical details should normally be verified on site.
Construction drawing Information issued for construction. Later changes and site variations may not be included.
As-built drawing Intended record of completed construction. The accuracy and preparation process should still be considered.
Later alteration drawing Recorded modification to part of the structure. Earlier and later information may need to be coordinated.
Unverified sketch or survey Approximate observed arrangement. Should guide investigation rather than replace it.
The investigation plan should identify which assumptions are sufficiently supported by records and which must be checked physically.

Why Refurbishment Projects Need Verified Evidence

Refurbishment design often depends on existing structural capacity, concealed services, façade interfaces and undocumented alterations.
STRUCTinspect has discussed this wider issue in Structural Investigation for Office Retrofit: Beyond the Energy Model. Architectural, energy and services proposals may appear workable until actual slab construction, riser positions, structural depths or concealed interfaces are verified.
Investigation planning should therefore be coordinated with the proposed design rather than completed as an isolated testing exercise.

Why Is an Initial Site Inspection Important?

An initial site inspection checks whether the proposed investigation can be delivered safely and whether the available records reflect visible site conditions.
The inspection may identify:
  • Structural grids and element positions.
  • Visible changes from drawings.
  • Cracking, movement or deterioration.
  • Previous openings or repairs.
  • Surface finishes and encasements.
  • Congested services.
  • Restricted working areas.
  • Occupied or sensitive spaces.
  • Work-at-height requirements.
  • Potential access for scaffold or MEWPs.
  • Water, power and welfare availability.
  • Reinstatement and protection constraints.
The initial inspection may show that the preferred investigation position is inaccessible or that another method would provide better evidence.

What Should Be Recorded During the Initial Inspection?

  • General location photographs.
  • Proposed investigation points.
  • Fixed dimensions and structural references.
  • Surface materials and finishes.
  • Visible services and obstructions.
  • Potential exclusion zones.
  • Access routes for equipment.
  • Conditions above and below the work.
  • Requirements for permits or isolations.
  • Any inconsistency with the investigation drawings.
This information allows the scope, method and quotation to be refined before mobilisation.

Why Are Structural Investigations Often Planned in Stages?

A staged investigation reduces unnecessary damage and allows later work to respond to initial findings.
Stage Typical Activities Purpose
Stage 1: Desk study Review drawings, reports, loading information and history. Identify assumptions, contradictions and information gaps.
Stage 2: Visual and dimensional survey Inspect visible construction, defects, access and dimensions. Confirm site conditions and refine investigation points.
Stage 3: Non-destructive investigation Scanning, cover surveys, monitoring and other surface tests. Map concealed features and target intrusive work.
Stage 4: Intrusive verification Breakouts, cores, inspection openings, trial pits and samples. Physically confirm critical dimensions, materials and details.
Stage 5: Additional targeted work Further testing prompted by unexpected or variable findings. Resolve remaining uncertainties before final assessment.
Stage 6: Engineering assessment Review results, calculations and proposed design. Reach conclusions and identify design, repair or strengthening requirements.
The project may pause after each stage so the engineer can review whether the next stage remains necessary or needs to be modified.

Why Not Begin with Intrusive Opening-Up?

Starting with uncontrolled intrusive work can produce openings in the wrong locations, damage important features and increase reinstatement requirements.
Non-destructive investigation may first establish:
  • The direction of reinforcement.
  • Possible bar or tendon locations.
  • The location of embedded services.
  • Approximate element thickness.
  • The most representative areas.
  • Areas of congestion or uncertainty.
This allows intrusive openings to be smaller, safer and more targeted.

How Are Investigation Methods Selected?

The method should be selected according to the information required, structural material, access conditions and acceptable level of disruption.
Required Information Potential Method Important Qualification
Reinforcement location GPR or electromagnetic cover meter. Exact diameter and condition may require breakout confirmation.
Concrete strength Concrete cores and laboratory testing. Sampling quantity and locations must be representative.
Slab thickness GPR, ultrasonic methods, cores or drilled measurement. Non-destructive values may require physical calibration.
Steel connection detail Removal of finishes, fire protection or encasement. Opening must expose the complete relevant connection.
Wall build-up Borescope hole or controlled opening-up. One opening may not represent variable wall construction.
Foundation dimensions Trial pit or controlled excavation. Temporary works and stability controls may be required.
Concrete deterioration Cover survey, carbonation, chloride, half-cell and breakout inspection. Results should be assessed together rather than individually.

Planning Concrete Scanning

Concrete scanning should have a defined feature, area and required output.
The planning information should include:
  • The element to be scanned.
  • The purpose of the survey.
  • The required survey dimensions.
  • The expected reinforcement or tendon arrangement.
  • The required investigation depth.
  • Accessible survey faces.
  • Surface finishes.
  • The required grid spacing.
  • Whether physical verification is permitted.
  • The required report and drawings.
For more detail on the types of concealed features that may be identified, read What Can a Concrete Scanner Detect?.
Scanning should not be specified simply as a guarantee that an area is clear. The method has limitations, particularly where features are deep, closely spaced or masked by shallow reinforcement.

Planning Concrete Breakouts

A concrete breakout should identify:
  • The exact bar or reinforcement layer to be exposed.
  • The opening width, length and maximum depth.
  • Whether links, laps or couplers must be located.
  • Measurements required.
  • Condition observations required.
  • The permitted tools.
  • The stop conditions.
  • The required repair system.
The breakout should normally be preceded by scanning so the opening can target the required reinforcement without cutting or damaging it.

Planning Concrete Core Sampling

Core sampling should be coordinated with both the structural engineer and the laboratory.
The specification should state:
  • Core diameter.
  • Required length.
  • Core orientation.
  • Number of samples.
  • Target structural elements or concrete pours.
  • Whether reinforcement may be present.
  • Required laboratory tests.
  • Sample storage and transport requirements.
  • Hole repair requirements.
The core position should provide representative concrete while avoiding significant reinforcement, tendons and services.

Planning Steel Connection Opening-Up

A connection investigation should identify which components need to be exposed.
The engineer may require confirmation of:
  • Member section size.
  • End plate or fin plate dimensions.
  • Bolt quantity and diameter.
  • Bolt spacing and edge distances.
  • Weld size and length.
  • Bearing length.
  • Stiffeners.
  • Corrosion or physical damage.
  • Fire-protection build-up.
The opening should be large enough to expose the required connection rather than only the most accessible section of the member.

Planning Masonry Investigations

Masonry investigations may need to confirm:
  • Wall thickness.
  • Solid or cavity construction.
  • Unit and mortar type.
  • Wall ties.
  • Embedded steelwork.
  • Lintel type and bearing.
  • Bonding at returns.
  • Support at floor and roof levels.
  • Previous infill or alteration.
Openings near arches, bearings, piers or slender sections may affect stability and should be approved by the structural engineer.

Planning Foundation Trial Pits

Trial pits should have defined dimensions, locations and excavation limits.
The brief should state:
  • The wall, column or foundation to be investigated.
  • The permitted excavation side.
  • Maximum width, length and depth.
  • Whether stepped or shored excavation is required.
  • Service information.
  • Groundwater controls.
  • Measurements and samples required.
  • Engineer inspection requirements.
  • Backfilling and compaction specification.
Excavation should not be extended beneath or along the foundation without engineer approval because this may remove support or disturb bearing material.

How Are Structural Investigation Locations Selected?

Locations should be selected to provide evidence that is relevant to the engineering decision.
Potential selection criteria include:
  • Areas of highest loading.
  • Support and connection zones.
  • Locations of visible defects.
  • Areas affected by proposed alterations.
  • Representative structural bays.
  • Different construction phases.
  • Locations where drawings are uncertain.
  • Areas with previous repairs.
  • Changes in element size or construction.
  • Locations that can be reinstated acceptably.
The easiest location to access may not be the most representative or structurally relevant location.

Representative Locations Versus Critical Locations

A representative location is selected because it is expected to reflect typical construction. A critical location is selected because it is important to the structural decision or presents greater risk.
Location Type Example Purpose
Representative A typical internal slab bay away from supports. Establish typical slab construction.
Critical The location of a proposed large penetration. Provide evidence for a specific alteration.
Defect-related An area of cracking, corrosion staining or movement. Investigate condition and possible cause.
Comparison An apparently sound area near a damaged location. Provide comparative evidence.
A balanced investigation may include several types of location.

Should Locations Be Marked on Drawings?

Yes. Each location should have a unique reference that appears consistently on:
  • The investigation brief.
  • Marked-up plans.
  • Site markings.
  • Photographs.
  • Sample labels.
  • Laboratory schedules.
  • The final report.
The reference system should remain clear if locations are moved or added. Revised locations should not reuse references in a way that creates ambiguity.

What If the Specified Location Cannot Be Used?

The brief should define how alternative positions are approved.
A location may need to move because of:
  • Embedded services.
  • Post-tensioning tendons.
  • Heavy reinforcement congestion.
  • Plant or fixed obstructions.
  • Hazardous materials.
  • Occupied areas.
  • Inadequate access.
  • Structural instability.
  • Finishes that cannot be disturbed.
The operative should not select a replacement solely for convenience. The revised position should remain technically representative and should be approved by the responsible engineer or project representative.

How Many Investigation Locations Are Required?

There is no universal number of investigation points suitable for every building.
The quantity depends on:
  • The size of the structure.
  • Expected variability.
  • Number of construction phases.
  • Reliability of drawings.
  • Proposed loading or alterations.
  • Importance of the structural decision.
  • Distribution of visible defects.
  • Accessibility.
  • Results from the initial investigation stage.
The number should be sufficient to support the intended decision but proportionate to disruption and cost.

Why One Location Is Often Insufficient

One location confirms the condition or construction at that specific point. It may not represent:
  • Other structural bays.
  • Different concrete pours.
  • Support zones.
  • Perimeter construction.
  • Different building phases.
  • Areas affected by later alterations.
  • Defective or water-exposed locations.
The engineer should assess whether repeated locations or comparison areas are required.

How a Staged Quantity Can Be Used

The initial scope may define a minimum number of locations with an option for additional testing.
Further locations may be triggered where:
  • Construction differs from drawings.
  • Results vary significantly.
  • A defect is more extensive than expected.
  • A connection cannot be fully exposed.
  • Samples are unsuitable for testing.
  • The proposed design changes.
  • The engineer requires confirmation in another structural zone.
This approach provides flexibility without authorising uncontrolled scope expansion.

How Does Access Affect Investigation Planning?

The required technical work may only be possible if suitable access is provided.
Planning should consider:
  • Floor and room access.
  • Ceiling removal.
  • Scaffold or mobile towers.
  • MEWP access.
  • Temporary platforms.
  • Roof access.
  • Confined spaces.
  • Excavation access.
  • Occupied areas.
  • Security restrictions.
  • Delivery routes for equipment.
The access system should allow the operative to control equipment, measure the exposed construction and photograph the findings safely.

Who Provides Access Equipment?

Responsibility should be agreed before pricing and mobilisation.
The project should state who provides:
  • Scaffold.
  • MEWPs.
  • Temporary platforms.
  • Ceiling removal.
  • Floor protection.
  • Service isolations.
  • Lighting.
  • Power and water.
  • Traffic management.
  • Welfare.
Unclear responsibilities can result in aborted attendance or methods being changed after mobilisation.

Occupied Building Constraints

Investigations in occupied buildings may require:
  • Out-of-hours working.
  • Noise restrictions.
  • Dust enclosures.
  • Protection of furniture and equipment.
  • Water and slurry containment.
  • Fire-alarm isolation.
  • Temporary closure of rooms or routes.
  • Security escorts.
  • Daily making-safe and cleaning.
These requirements should be reflected in programme, cost and method selection.

Planning Work Above and Below a Slab

Drilling, coring or opening a slab can affect both the work face and the area on the opposite side.
The project should confirm:
  • What is located below or above the work.
  • Whether the area is occupied.
  • Whether services are present.
  • Whether falling debris or water can be contained.
  • Whether an exclusion zone is required.
  • Whether both faces need to be inspected or scanned.
  • Whether temporary support is required.

How Are Structural Risks Considered?

Some investigation activities can affect the structure rather than merely inspect it.
Potentially significant activities include:
  • Breaking out around reinforcement.
  • Cutting concrete cores.
  • Exposing connections.
  • Removing masonry near bearings.
  • Excavating beside foundations.
  • Removing façade supports.
  • Loading floors with equipment or reaction plant.
  • Removing fire protection or structural encasement.
The structural engineer should identify maximum opening sizes, sequences, temporary works and stop conditions.

Temporary Works During Investigations

Temporary works may be required where the investigation could reduce support or stability.
Examples include:
  • Propping below a major concrete breakout.
  • Supporting masonry near a bearing.
  • Shoring a foundation trial pit.
  • Supporting façade panels during connection exposure.
  • Providing a designed loading platform.
  • Supporting removed floor or roof finishes.
The temporary works design and installation sequence should be completed before the investigation activity begins.

Embedded Service Risks

Investigation planning should include review of embedded and concealed services.
Possible controls include:
  • Service drawings.
  • Building-operator information.
  • Concrete scanning.
  • Cable-avoidance tools.
  • Signal generators.
  • Isolation procedures.
  • Permit-to-drill systems.
  • Controlled drilling depth.
Scanning may locate a possible service route without confirming whether it is live or pressurised. Isolation responsibility should remain with the appropriate project team.

Post-Tensioning Risks

Post-tensioned structures require additional planning because tendons contain stored force and form part of the structural system.
The project should provide:
  • Post-tensioning drawings.
  • Tendon and anchorage layouts.
  • Available stressing records.
  • A suitable GPR survey.
  • Approved penetration locations.
  • Defined drilling depths.
  • Structural or post-tensioning specialist review.
Unidentified or tendon-like responses should be treated conservatively rather than investigated using uncontrolled drilling.

Hazardous-Material Planning

Intrusive work may disturb concealed hazardous materials.
The project should confirm appropriate survey information for:
  • Asbestos-containing materials.
  • Lead coatings.
  • Historic fire-protection products.
  • Contaminated soil.
  • Silica-containing dust.
  • Biological contamination.
A general management survey may not be sufficient where the planned work will disturb concealed construction.

How Are RAMS Developed for a Structural Investigation?

The RAMS should translate the technical brief into a practical, controlled site method.
It should identify:
  • The exact work locations.
  • The investigation sequence.
  • Equipment and tools.
  • Access arrangements.
  • Services and post-tensioning controls.
  • Maximum drilling or opening depths.
  • Dust, noise, vibration and water controls.
  • Temporary works.
  • Exclusion zones.
  • Falling-object controls.
  • Stop conditions.
  • Sample handling.
  • Making-safe and reinstatement.
  • Emergency arrangements.
STRUCTinspect has explained the importance of connecting technical methodology to real site responsibilities in What a Structural Testing RAMS Must Contain Before Loading Starts. The same principle applies to investigation work even where no structural load test is involved.

Why Generic RAMS Are Often Inadequate

Generic wording may describe drilling, coring or breaking but fail to identify:
  • The actual structural element.
  • The permitted opening size.
  • The maximum depth.
  • The tendon or service risk.
  • The required temporary support.
  • The opposite-side conditions.
  • The stop-and-review process.
  • The repair requirement.
The method should reflect the investigation brief and actual site conditions.

Planning Stop Conditions

Stop conditions should be defined before work begins.
Work may need to stop if:
  • Unexpected reinforcement is encountered.
  • A tendon-like feature is identified.
  • An unknown service is exposed.
  • The construction differs from drawings.
  • Movement or instability is observed.
  • Hazardous material is suspected.
  • The opening reaches its permitted dimensions without exposing the required detail.
  • The sample is damaged or unsuitable.
  • Water or contamination enters the work area.
The operative should know who must be contacted and what evidence should be recorded before work resumes.

How Is Structural Sampling Planned?

Sampling should be planned with the laboratory before extraction where possible.
The laboratory may need to advise on:
  • Minimum sample dimensions.
  • Number of samples.
  • Orientation.
  • Preparation requirements.
  • Storage conditions.
  • Transport times.
  • Test standards.
  • Whether damaged or reinforced samples are acceptable.
A sample that is too small, damaged or taken from the wrong location may not provide a valid result.

Sample Location and Representativeness

Sample locations should reflect the material or condition being assessed.
The plan may distinguish between:
  • Typical material.
  • Areas of visible deterioration.
  • Different concrete pours.
  • Different elevations or exposure conditions.
  • Original and repaired construction.
  • Wet and dry zones.
  • Comparison locations.
Sampling only the easiest or best-looking area can provide misleading confidence.

Sample Identification and Traceability

Each sample should receive a unique reference linked to:
  • The project.
  • The structural element.
  • The exact location.
  • The depth and orientation.
  • The extraction date.
  • Photographs.
  • The requested test.
  • The laboratory submission record.
Poor traceability can make an otherwise valid laboratory result unusable.

Chain of Custody

The project may require a documented chain of custody showing who extracted, labelled, transported and received each sample.
This becomes particularly important where results support:
  • Structural design.
  • Insurance or legal assessment.
  • Compliance decisions.
  • Defect investigations.
  • Contractual disputes.

Planning Reinstatement

The reinstatement strategy should be agreed before intrusive work begins.
The project should identify:
  • Who completes the repair.
  • Whether the opening remains available for engineer inspection.
  • The temporary making-safe requirement.
  • The repair material or system.
  • Required structural performance.
  • Fire, acoustic and thermal requirements.
  • Waterproofing requirements.
  • Finish and decoration requirements.
  • Curing and protection.
  • Inspection and acceptance responsibility.
A cosmetic patch may not restore the original structural, fire or durability performance.

Temporary Making-Safe

Where permanent repair cannot be completed immediately, the plan may require:
  • Temporary covers.
  • Barriers.
  • Weatherproofing.
  • Temporary fire stopping.
  • Edge protection.
  • Warning labels.
  • Inspection and handover records.
Temporary protection should not be described as permanent reinstatement.

How Is the Reporting Output Planned?

The report requirements should be agreed before site work so the correct measurements, photographs and references are collected.
The report may need to include:
  • Project and investigation objectives.
  • Documents reviewed.
  • Investigation locations.
  • Methods and equipment.
  • Site conditions and access limitations.
  • Visual observations.
  • Measured dimensions.
  • Scanning results.
  • Opening-up findings.
  • Sample references.
  • Laboratory results.
  • Photographs and drawings.
  • Differences from record information.
  • Unexpected findings.
  • Reinstatement status.
  • Limitations.
  • Recommendations for additional work.
The report should distinguish measured evidence from engineering interpretation.

What Photographs Should Be Planned?

A useful photographic sequence includes:
  • A general location view.
  • The investigation point before work.
  • Surface markings and scanner findings.
  • Progressive stages of opening-up.
  • The fully exposed detail.
  • Measurements with a visible scale.
  • Samples and labels.
  • Unexpected defects or construction.
  • The repaired or made-safe opening.
Photographs should provide both context and close technical detail.

How Are Unexpected Findings Managed?

Investigation planning should expect the possibility that site construction will differ from records.
The process should identify:
  • Who is notified.
  • Whether work stops immediately.
  • What photographs and measurements are required.
  • Whether the opening should remain accessible.
  • Who approves additional work.
  • How changes are recorded commercially and technically.
The investigation team should not extend the work automatically because a feature was not found at the expected location.

Planning the Engineer’s Review

Some openings may need to remain available for inspection by the structural engineer before reinstatement.
The plan should confirm:
  • Whether live or remote inspection is acceptable.
  • The notice period required.
  • The photographs and dimensions needed.
  • Whether the engineer must approve closure.
  • What happens if the finding differs from expectations.
Closing an opening before the required inspection may result in repeat work.

Programme and Laboratory Lead Times

Investigation programmes should allow for more than the site attendance.
The sequence may include:
  • Document review.
  • Site inspection.
  • Preparation and approval of RAMS.
  • Permits and isolations.
  • Access installation.
  • Non-destructive surveys.
  • Intrusive work.
  • Engineer inspection.
  • Sample transport.
  • Laboratory testing.
  • Result review.
  • Additional investigation where required.
  • Reporting and structural assessment.
Laboratory testing and additional investigation can affect the design programme if not considered early.

How Should the Investigation Be Priced?

A clear scope allows the quotation to identify what is included and what may create additional cost.
The quotation should clarify:
  • Number and type of locations.
  • Scanning areas.
  • Opening or core dimensions.
  • Site attendance duration.
  • Access assumptions.
  • Out-of-hours working.
  • Laboratory testing.
  • Waste and sample transport.
  • Temporary protection.
  • Reinstatement.
  • Reporting format.
  • Rates for additional locations.
  • Abortive attendance conditions.
Ambiguous scopes often create disagreement over whether scanning, repairs, access, reports or laboratory fees were included.

Common Structural Investigation Planning Mistakes

Planning Mistake Why It Causes Problems Better Approach
No defined engineering question. Testing may not provide the information required for the decision. Work backwards from the proposed assessment or alteration.
Vague location descriptions. The wrong element or area may be investigated. Use marked-up drawings, grids and unique references.
Starting with uncontrolled opening-up. Damage may occur without answering the engineering question. Use a staged strategy with non-destructive mapping first.
Selecting only convenient locations. Results may not represent critical or variable construction. Select representative, critical and defect-related areas.
No opening dimensions. Too much or too little material may be removed. Specify width, length, depth and stop conditions.
No access review. The investigation may not be achievable when the team arrives. Complete a preliminary inspection and assign access responsibilities.
No service or tendon information. Drilling and breakout work may damage concealed systems. Review records, scan and use permit controls.
No laboratory coordination. Samples may be too small, damaged or prepared incorrectly. Confirm sample requirements before extraction.
No reinstatement scope. Openings may remain unsafe or compromise performance. Agree temporary and permanent repair responsibilities.
No process for unexpected findings. Operatives may improvise or continue into unsafe construction. Define stop, record, review and approval steps.

Structural Investigation Planning Checklist

  • Engineering objective: state the decision the investigation must support.
  • Proposed works: describe the loading, alteration, repair or demolition proposal.
  • Responsible engineer: identify who specifies and interprets the investigation.
  • Desk study: review drawings, reports, repairs and alteration records.
  • Drawing reliability: distinguish design information from verified as-built records.
  • Initial inspection: confirm access, visible construction and site restrictions.
  • Staged strategy: plan visual, non-destructive and intrusive phases.
  • Methods: select tests that provide the information required.
  • Locations: mark representative, critical and defect-related positions.
  • References: assign unique identifiers to every investigation point.
  • Quantities: define minimum locations and triggers for additional work.
  • Opening dimensions: specify size, depth, orientation and stop conditions.
  • Scanning: identify reinforcement, tendons and services before intrusive work.
  • Access: assign responsibility for scaffold, MEWPs, platforms and ceiling removal.
  • Occupied areas: define noise, dust, water and working-hour restrictions.
  • Structural stability: identify temporary works and sequencing requirements.
  • Services: provide drawings, detection and isolation controls.
  • Post-tensioning: provide tendon information and specialist review.
  • Hazardous materials: confirm suitable intrusive survey information.
  • RAMS: connect the technical scope to actual site methods and controls.
  • Samples: agree dimensions, quantities, labels and laboratory tests.
  • Inspection hold points: confirm when engineer review is required.
  • Unexpected findings: define the stop-and-review process.
  • Reinstatement: agree temporary making-safe and permanent repairs.
  • Reporting: define photographs, drawings, measurements and final deliverables.
  • Programme: include approvals, access, laboratory work and additional investigation.
  • Commercial scope: clarify exclusions and rates for additional work.

Evidence-Based Summary

Structural investigations should be planned around a defined engineering question and the decision that the findings must support.
The planning process normally includes a desk study, initial site inspection, non-destructive surveys, targeted intrusive work, laboratory testing and engineering assessment.
Investigation locations should be structurally relevant and representative rather than selected only because they are easy to access.
Every opening, core, sample and scan should have a defined location, size, method, output and review route.
Access, temporary works, services, post-tensioning, hazardous materials and conditions on the opposite side of the work should be reviewed before mobilisation.
A staged strategy allows the scope to respond to unexpected findings while reducing unnecessary damage and cost.
The strongest investigation plans connect the engineering objective, site method, sample traceability, reporting requirements and reinstatement strategy into one coordinated process.

FAQ: Planning Structural Investigations

Who should plan a structural investigation?
The responsible structural engineer or designer should normally define or approve the information, methods, locations and quantities required for the assessment.
What is the first step in planning an investigation?
The first step is defining the engineering question and the decision that the investigation findings must support.
Why is a desk study required?
A desk study identifies existing information, contradictions, previous alterations and gaps that need to be verified on site.
Should drawings be trusted as exact as-built information?
Not automatically. Drawings may show design intent, while construction changes and later alterations may not have been recorded.
Why are investigations carried out in stages?
A staged approach uses initial findings to target later work, reduce unnecessary damage and respond to unexpected construction.
Should scanning be completed before opening-up?
Where concrete contains reinforcement, tendons or possible services, scanning should normally be completed before drilling, coring or breakout work.
How are investigation locations selected?
Locations should be selected according to structural relevance, proposed work, visible defects, construction variability and the reliability of existing information.
How many investigation points are required?
The quantity depends on the size and variability of the structure, the proposed decision and the confidence provided by the available records.
Can an operative move an investigation location?
A location may need to move because of access, services or tendons, but the alternative should remain technically relevant and be approved through the agreed process.
Who should specify concrete core dimensions?
The structural engineer or materials specialist should coordinate the core diameter, length, quantity and required tests with the laboratory.
Do structural investigations require RAMS?
Yes, where site activities involve scanning, drilling, coring, breakout, excavation, access equipment or other controlled work. The RAMS should reflect the project-specific scope and risks.
When are temporary works required?
Temporary works may be required where opening-up, excavation, loading or removal of construction could affect stability or support.
What should happen if unexpected construction is found?
Work should stop at the agreed safe point, the finding should be recorded and the responsible engineer or project representative should review the next step.
Should reinstatement be planned before opening-up?
Yes. The project should define temporary making-safe, permanent repair, required performance and responsibility before the opening is formed.
Why must samples have unique references?
Unique references link laboratory results to the correct structural element, location, depth and investigation record.
What should the final investigation report include?
It should include the objectives, reviewed information, methods, locations, measurements, scan findings, opening-up results, samples, photographs, limitations and recommended further work.
Does an investigation report provide structural approval?
The investigation report provides evidence. The responsible structural engineer should use that evidence to assess capacity, design alterations and provide engineering conclusions.

Source Context and Editorial Note

This article is a STRUCTinspect technical explainer covering the planning of structural investigations for existing buildings, refurbishment, temporary works, demolition and structural assessment.
It provides general construction information rather than a project-specific investigation specification. Methods, test quantities, locations, opening dimensions, sampling, temporary works, access and reporting requirements should be selected for the particular structure and engineering objective.
This article does not provide structural engineering, temporary works, hazardous-material, post-tensioning, health and safety, contractual or construction advice. Structural investigations should be planned, reviewed and interpreted by the appropriate structural engineer, designer, materials specialist, contractor or competent professional responsible for the works.