Structural opening-up works involve the controlled removal of finishes, coverings or structural materials so that concealed construction can be inspected, measured and recorded directly.
The work may be as limited as removing a section of plasterboard to inspect a steel connection, or as substantial as forming a concrete breakout, opening masonry around a bearing or excavating beside an existing foundation.
Opening-up is commonly used during refurbishment, structural assessment, façade remediation, demolition planning, temporary works design and investigations into cracking, corrosion, water ingress or undocumented construction.
The key point is this: opening-up should be planned to answer a defined engineering question. The location, dimensions, depth, sequence, measurements, stop conditions and reinstatement requirements should be agreed before material is removed.

What Are Structural Opening-Up Works?

Structural opening-up works are intrusive investigation activities used to expose concealed parts of a building or structure.
They may involve removing:
  • Plasterboard and dry lining.
  • Suspended ceilings.
  • Floor finishes and screeds.
  • Plaster or render.
  • Concrete cover.
  • Masonry units or mortar.
  • Fire-protection boards or coatings.
  • Roof finishes.
  • Façade panels and internal linings.
  • Floorboards and timber decking.
  • Insulation and membranes.
  • Local ground or backfill beside foundations.
The objective is not simply to create an opening. It is to reveal enough of the concealed construction to answer a defined technical question.

Opening-Up Works Versus a Visual Survey

A visual survey records the construction and defects that can already be seen. Opening-up exposes details hidden by finishes, encasement, concrete, masonry, ground or other materials.
Investigation Type Typical Evidence Main Limitation
Visual survey Visible defects, geometry, finishes and exposed construction. Concealed details remain unknown.
Non-destructive survey Estimated reinforcement, interfaces, thickness and concealed feature positions. Some findings remain indirect or interpreted.
Opening-up works Direct inspection and measurement of concealed construction. Evidence is local to the opened area and requires repair.
The three approaches are often used together. Visual and non-destructive work can help select where intrusive opening-up will provide the greatest value.

Why Are Structural Opening-Up Works Required?

Opening-up may be required where drawings and non-destructive surveys do not provide enough confidence for a structural or construction decision.
Typical reasons include:
  • Confirming how a steel beam is connected.
  • Exposing reinforcement within concrete.
  • Confirming the build-up of a slab, wall or roof.
  • Determining whether a wall is loadbearing.
  • Inspecting a lintel or bearing detail.
  • Confirming façade brackets and anchors.
  • Inspecting timber joist ends or roof members.
  • Checking fire protection around steelwork.
  • Investigating water ingress or corrosion.
  • Confirming foundation dimensions.
  • Checking undocumented alterations.
  • Supporting demolition or temporary works design.
The structural engineer should define what evidence is needed and how it will be used.

What Questions Can Opening-Up Answer?

Engineering Question Possible Opening-Up Method Evidence Obtained
How is the beam connected? Remove ceiling and local fire protection. Connection plates, bolts, welds, bearings and member geometry.
What reinforcement is present? Controlled concrete breakout. Bar diameter, spacing, cover, arrangement and condition.
What is inside the wall? Local wall opening or borescope access. Layers, cavities, framing, insulation, ties and services.
How does the façade connect? Remove local façade or internal lining. Bracket, anchor, rail and substrate arrangement.
What foundation is present? Trial pit or controlled excavation. Foundation type, width, depth and founding level.
Is concealed timber decayed? Lift flooring or open wall and ceiling finishes. Timber dimensions, moisture, bearing and visible deterioration.

Types of Structural Opening-Up Works

Opening-up may be classified by the material or concealed detail being investigated.
  • Concrete reinforcement breakouts.
  • Concrete core openings.
  • Steel connection exposure.
  • Masonry opening-up.
  • Timber floor and roof openings.
  • Façade and cladding investigations.
  • Fire-protection removal.
  • Foundation trial pits.
  • Roof and waterproofing openings.
  • Borescope or endoscope inspection holes.
  • Service and riser investigations.
  • Anchor and fixing exposure.

Local Inspection Opening

A local inspection opening is intended to expose a small area of concealed construction with limited disruption.
It may be suitable for confirming:
  • Wall or ceiling build-up.
  • Presence of insulation.
  • Member position.
  • Cavity depth.
  • Service routes.
  • Local water damage.
  • Visible condition of a fixing or bracket.
A small opening may not reveal the complete structural detail. Its dimensions should be matched to the information required.

Extended Structural Opening

A larger opening may be needed to expose an entire connection, several reinforcement bars, a bearing length or multiple construction layers.
The larger the opening, the greater the potential impact on:
  • Structural stability.
  • Fire resistance.
  • Acoustic separation.
  • Weatherproofing.
  • Dust and noise.
  • Occupancy.
  • Repair scope and programme.
Extended openings should therefore be specifically designed and approved rather than created by gradually enlarging an undefined inspection hole.

How Are Structural Opening-Up Works Planned?

Planning should begin with the information required by the structural engineer, not with the easiest material to remove.
The opening-up brief should state:
  • The engineering purpose.
  • The building, level, grid and structural element.
  • The exact opening location.
  • The required length, width, diameter and depth.
  • The construction layers to be removed.
  • The concealed feature to be exposed.
  • The measurements and photographs required.
  • Acceptable alternative locations.
  • Temporary works requirements.
  • Inspection hold points.
  • Stop conditions.
  • Reinstatement requirements.
  • The final reporting output.
A vague instruction to “open up and confirm construction” can result in an opening that is too small, incorrectly located or unable to answer the intended question.

Who Should Specify the Opening?

The structural engineer or designer responsible for the assessment should normally specify or approve the opening location and dimensions.
The investigation contractor may advise on:
  • Practical access.
  • Suitable tools.
  • Likely opening dimensions.
  • Dust and debris controls.
  • Scanning requirements.
  • Repair implications.
  • Potential programme constraints.
However, the contractor should not be expected to decide whether removing structural material is acceptable without engineering instruction.

Reviewing Existing Information

Before opening-up, the project should review available:
  • Structural drawings.
  • Architectural drawings.
  • Reinforcement drawings.
  • Post-tensioning layouts.
  • Service drawings.
  • Façade drawings.
  • Fire-strategy information.
  • Previous investigation reports.
  • Repair records.
  • Hazardous-material surveys.
  • Alteration and refurbishment records.
The drawings guide the opening-up, but critical details should be checked against actual site evidence.
Related STRUCTinspect Guidance
STRUCTinspect has discussed the importance of verified existing-building evidence in Structural Investigation for Office Retrofit: Beyond the Energy Model. Opening-up often becomes necessary where structural, services and façade assumptions cannot be confirmed reliably from record information alone.

Why the Opening Dimensions Must Be Defined

The opening should be large enough to expose the required detail but no larger than reasonably necessary.
Required Detail Likely Opening Requirement Risk if Undersized
Steel member identification Expose enough of the flange and web to measure the section. Only part of the section is visible and the member cannot be identified.
Beam connection Expose the beam end, connection plate, bolts or welds and support. The member is visible but the load-transfer detail remains concealed.
Reinforcement spacing Expose at least two adjacent bar centrelines. Only one bar is exposed and spacing cannot be verified.
Wall build-up Pass through all required layers while maintaining safe edges. The opening stops within a lining or cavity and the structure remains unknown.
Foundation profile Expose the side and underside level where permitted. Foundation depth or width cannot be established.
If the approved dimensions are reached without exposing the required detail, the opening should not be enlarged automatically. The engineer should review the next step.

Selecting Opening-Up Locations

Locations should be selected because they are relevant to the engineering assessment.
The investigation may target:
  • Representative structural bays.
  • Support and connection zones.
  • Areas affected by proposed alterations.
  • Locations of cracking or deterioration.
  • Different construction phases.
  • Previous repairs or modifications.
  • Façade support zones.
  • Areas where drawings are uncertain.
  • Comparison areas away from visible defects.
The most accessible location may not be structurally representative.

How Many Openings Are Required?

There is no universal number. The required quantity depends on:
  • The size of the structure.
  • The expected construction variability.
  • The number of structural zones.
  • The reliability of available drawings.
  • The proposed engineering decision.
  • The distribution of visible defects.
  • The results of initial openings.
  • Access and reinstatement constraints.
A staged approach may begin with selected openings and add further locations where the findings differ from expectations.

Engineer Inspection Hold Points

Some openings should remain accessible until inspected by the responsible engineer.
The brief should confirm:
  • Whether the engineer will attend in person.
  • Whether photographs or video inspection are acceptable.
  • The notice period required.
  • The measurements needed before inspection.
  • Whether the opening may be enlarged only after review.
  • Whether written approval is required before reinstatement.
Closing the opening before the required inspection may result in repeat work.

Should Concrete Be Scanned Before Opening-Up?

Concrete should normally be scanned before drilling, cutting or breaking where reinforcement, post-tensioning tendons or embedded services may be present.
Scanning can help identify:
  • Reinforcement position and direction.
  • Approximate concrete cover.
  • Possible reinforcement layers.
  • Post-tensioning tendons or ducts.
  • Embedded services.
  • Areas of heavy congestion.
  • Possible clear zones for initial access.
For a wider explanation of scanner outputs and limitations, read What Can a Concrete Scanner Detect?.
Scanning reduces risk but does not guarantee that every small, deep or masked feature will be identified. The opening should still proceed using controlled depths and stop conditions.

Service Drawings and Isolation

Opening-up can expose or damage electrical, mechanical, hydraulic and communication services.
The project may need to provide:
  • Current service drawings.
  • Electrical detection.
  • Signal-generator tracing.
  • Concrete scanning.
  • Building-operator information.
  • Isolation certificates.
  • Permit-to-drill or permit-to-break-out approval.
A concealed feature identified by scanning may not be conclusively identifiable as a service, reinforcement bar or tendon. Uncertain responses should be treated conservatively.

Post-Tensioning Controls

Post-tensioned concrete requires additional control because tendons contain stored force and form part of the structural system.
Before opening-up, the project should review:
  • Post-tensioning drawings.
  • Tendon profiles.
  • Anchorage and stressing locations.
  • GPR findings.
  • Permitted opening dimensions and depth.
  • Structural or post-tensioning specialist approval.
A tendon-like response should not be exposed using uncontrolled breaking.

Hazardous-Material Information

Opening-up can disturb concealed hazardous materials that are not visible during an ordinary inspection.
Potential materials include:
  • Asbestos-containing boards and insulation.
  • Asbestos coatings or fire protection.
  • Lead-based paint.
  • Silica-containing concrete and masonry dust.
  • Contaminated soil.
  • Historic sealants and mastics.
  • Biological contamination.
The project should confirm that appropriate intrusive hazardous-material information is available before work begins.

Concrete Opening-Up Works

Concrete opening-up may be used to expose reinforcement, confirm slab build-up, inspect cracking, extract samples or access concealed structural details.
Common methods include:
  • Local concrete breakouts.
  • Diamond-drilled inspection holes.
  • Concrete core extraction.
  • Controlled saw cutting.
  • Small borescope holes.
  • Removal of repair mortar.

Concrete Reinforcement Breakouts

A reinforcement breakout removes the concrete cover around selected steel so it can be measured and inspected directly.
The opening may confirm:
  • Bar diameter.
  • Bar spacing.
  • Concrete cover.
  • Reinforcement direction.
  • Links and reinforcement layers.
  • Laps and couplers where sufficiently exposed.
  • Corrosion and local section loss.
  • Condition of surrounding concrete.
Concrete should be removed progressively, with smaller and lower-impact tools used as the reinforcement is approached.

Concrete Cores as Opening-Up Works

A concrete core may provide a physical sample and create a local opening through the structural element.
Cores may be used to investigate:
  • Concrete compressive strength.
  • Element thickness.
  • Layered construction.
  • Carbonation or chloride content.
  • Internal cracking.
  • Material composition.
  • Interfaces between pours or materials.
Core diameter, orientation, depth, location and laboratory requirements should be specified before drilling.

Saw Cutting Around Concrete Openings

Saw cutting may create defined edges, but cutting depth must be controlled because shallow reinforcement, tendons and services may be present.
The method should confirm:
  • The maximum permitted blade depth.
  • The reinforcement cover.
  • The location of tendons and services.
  • The required edge profile.
  • How corner overcuts will be prevented.
  • How slurry will be contained.
Saw cutting should not be treated as safe merely because the required structural opening is shallow.

What If Reinforcement Is Encountered?

Reinforcement should not be cut automatically when it obstructs an opening.
Where steel is encountered unexpectedly:
  • Work should stop.
  • The bar should be photographed.
  • Its position and dimensions should be recorded.
  • The responsible engineer should be notified.
  • The opening should not be enlarged or redirected without approval.
Any accidental damage to reinforcement should be reported before the area is repaired.

Opening-Up Existing Steelwork

Structural steel members and connections are frequently concealed behind ceilings, wall linings, cladding, concrete encasement or fire protection.
Opening-up may be used to confirm:
  • Member section size and type.
  • Plate dimensions.
  • Bolt quantity and diameter.
  • Bolt spacing and edge distances.
  • Weld location and extent.
  • Bearing length.
  • Stiffeners and cleats.
  • Corrosion and physical damage.
  • Relationship with surrounding concrete or masonry.
  • Fire-protection thickness and condition.

Exposing a Steel Connection

The opening should expose the connection rather than only the member.
For example, seeing the lower flange of a beam may not confirm:
  • Whether the beam is seated or end-plated.
  • How many bolts are present.
  • Whether welds exist.
  • The bearing length.
  • Whether stiffeners are installed.
  • How loads transfer into the support.
The engineer should identify the components that must be visible before the opening dimensions are agreed.

Removing Fire Protection

Fire-protection systems may include boards, spray-applied materials, encasement or intumescent coatings.
Before removal, the project should confirm:
  • The material type.
  • Hazardous-material information.
  • The permitted removal area.
  • Containment and PPE requirements.
  • The inspection hold point.
  • The reinstatement system.
  • Who will inspect or certify the repair.
The opening should not leave an unrecorded or unprotected fire-resistance defect.

Measuring Existing Steel Members

The survey may record:
  • Overall depth.
  • Flange width and thickness.
  • Web thickness.
  • Plate dimensions.
  • Bolt diameters and spacing.
  • Weld size where accessible.
  • Bearing dimensions.
  • Coating and corrosion condition.
Measurements should be supported by clear photographs and sketches showing where each dimension was taken.

Masonry Opening-Up Works

Masonry opening-up may be required to investigate wall construction, bearings, lintels, ties, embedded steelwork or previous alterations.
The opening may confirm:
  • Wall thickness.
  • Solid or cavity construction.
  • Brick, block or stone arrangement.
  • Bond pattern.
  • Mortar type and condition.
  • Wall ties and restraint fixings.
  • Lintel type and bearing.
  • Embedded columns or beams.
  • Infilled openings.
  • Connection with floors, roofs and returns.

Opening Masonry Near Bearings

Masonry around a beam, lintel, arch or slab bearing forms part of the load-transfer zone.
The structural engineer should define:
  • The permitted opening dimensions.
  • The safe removal sequence.
  • Whether temporary support is required.
  • The minimum masonry to remain.
  • The inspection hold point.
  • The reinstatement method.
Operatives should not remove additional masonry to improve visibility without approval.

Investigating Wall Ties

A local masonry opening may expose wall ties so their type, spacing, embedment and condition can be inspected.
The opening may show:
  • Tie material and shape.
  • Embedment into each leaf.
  • Corrosion or deformation.
  • Insulation and cavity condition.
  • Mortar engagement.
One tie should not automatically be treated as representative of an entire elevation. Further locations or non-destructive tie surveys may be required.

Lintel Investigations

Opening-up above a door or window may be used to confirm:
  • Whether a lintel is present.
  • The lintel material and profile.
  • Bearing length.
  • Relationship with cavity construction.
  • Corrosion or cracking.
  • Whether separate inner and outer lintels are used.
Removing finishes or masonry around a lintel should be controlled because the opening may affect local support.

Timber Opening-Up Works

Timber floors, roofs and wall framing are often concealed by finishes and insulation.
Opening-up may confirm:
  • Joist or rafter dimensions.
  • Spacing and direction.
  • Bearing details.
  • Connections and trimmers.
  • Moisture condition.
  • Fungal decay.
  • Insect damage.
  • Splits or previous notching.
  • Historic repairs or strengthening.
  • Fire and acoustic build-up.

Inspecting Timber Joist Ends

Joist ends embedded in masonry can be vulnerable to concealed moisture and decay.
The opening may need to show:
  • The full bearing length.
  • The interface with masonry.
  • Visible decay or section loss.
  • Moisture sources.
  • Ventilation around the bearing.
  • Previous repairs or resin treatments.
A joist that appears sound at mid-span may still be significantly deteriorated at its concealed bearing.

Lifting Floorboards

Floorboards and finishes should be lifted with consideration for:
  • Hidden electrical and plumbing services.
  • Fragile or historic finishes.
  • Asbestos-containing floor products.
  • Fire and acoustic separation.
  • Temporary open-floor hazards.
  • Reinstatement and matching materials.
The opening should be made safe whenever it is left unattended.

Façade Opening-Up Works

Façade opening-up may expose brackets, anchors, rails, cavity barriers, insulation, membranes, fire stopping and the interface with the primary structure.
It may be required to confirm:
  • Bracket and rail arrangement.
  • Anchor type and embedment.
  • Connection to concrete, masonry or steel.
  • Cavity depth.
  • Insulation type and continuity.
  • Cavity barriers.
  • Membranes and weather seals.
  • Corrosion or water ingress.
  • Differences from façade drawings.

External and Internal Façade Access

Façade components may be opened from outside, inside or from both sides depending on the system.
The access strategy should consider:
  • Scaffold, MEWP or rope-access requirements.
  • Panel weight and support.
  • Falling-object risk.
  • Wind and weather.
  • Occupied internal areas.
  • Temporary weatherproofing.
  • Fire and compartmentation implications.
Panels and components should not be removed without understanding how they are supported and restrained.

Cavity Barrier and Fire-Stopping Investigations

An opening may be used to inspect the location, continuity and installation of cavity barriers or fire stopping.
The survey should record:
  • Product type where identifiable.
  • Position and orientation.
  • Fixing arrangement.
  • Compression or contact with adjacent surfaces.
  • Gaps and penetrations.
  • Relationship with insulation and membranes.
  • Visible damage or deterioration.
The investigation record should distinguish observation from a formal compliance assessment.

Foundation Opening-Up and Trial Pits

Foundation investigations commonly involve controlled excavation beside a wall, column base or other support.
A trial pit may confirm:
  • Foundation type.
  • Plan dimensions.
  • Depth and founding level.
  • Material and condition.
  • Relationship with the supported structure.
  • Adjacent foundations.
  • Ground conditions at the exposed face.
  • Evidence of movement or undermining.

Structural Risks of Trial Pits

Excavation can remove lateral support or disturb material beneath or beside the foundation.
The brief should define:
  • The maximum pit length, width and depth.
  • The permitted side of excavation.
  • Whether excavation beneath the foundation is prohibited.
  • The sequence of excavation.
  • Temporary shoring requirements.
  • Groundwater controls.
  • Engineer inspection requirements.
  • Backfill and compaction requirements.
The excavation should not be enlarged because the foundation was not found at the expected level without engineering review.

Underground Services

Trial pits and external openings require service checks before excavation.
Controls may include:
  • Utility drawings.
  • Cable-avoidance tools.
  • Signal-generator tracing.
  • Ground-penetrating radar.
  • Permit-to-dig procedures.
  • Hand excavation within defined zones.
Service records should be treated as guidance rather than proof of exact position.

Site Controls for Structural Opening-Up

Opening-up may involve drilling, cutting, breaking, excavation and work at height. The RAMS should reflect the actual work and structural context.
Typical controls include:
  • Permit-to-drill, permit-to-break-out or permit-to-dig procedures.
  • Service detection and isolation.
  • Post-tensioning review.
  • Maximum opening dimensions and depths.
  • Temporary works.
  • Dust and silica controls.
  • Noise and vibration controls.
  • Water and slurry containment.
  • Work-at-height arrangements.
  • Falling-object protection.
  • Exclusion zones.
  • Manual-handling controls.
  • Stop-work procedures.
  • Waste and sample handling.
  • Temporary making-safe.

Project-Specific RAMS

Generic wording is rarely sufficient for structural opening-up because the risks depend on the exact location, material, depth and concealed construction.
STRUCTinspect has discussed the importance of connecting technical work with real site controls in What a Structural Testing RAMS Must Contain Before Loading Starts.
Although opening-up is not necessarily a structural load test, the same operational principles apply:
  • The location and method must be clear.
  • Responsibilities must be assigned.
  • The equipment must match the task.
  • Hold points and stop conditions must be defined.
  • Unexpected findings must trigger review.

Work at Height

Soffit, roof and façade openings may require scaffold, MEWPs or temporary platforms.
The access system should allow:
  • Safe control of cutting and breaking tools.
  • Accurate measurement.
  • Safe handling of removed materials.
  • Tool restraint.
  • Debris containment.
  • Emergency access and recovery.
The platform must be suitable for the operative, equipment, removed materials and any temporary support system.

Dust and Silica Control

Cutting concrete and masonry can release respirable crystalline silica dust.
Controls may include:
  • Local dust extraction.
  • Suitable respiratory protective equipment.
  • Wet cutting or drilling where appropriate.
  • Sealed enclosures.
  • Negative-pressure units.
  • Vacuum cleaning using suitable equipment.
  • Restricted access to the work area.
Wet methods should not be used without considering electrical hazards, leakage and damage to occupied areas.

Noise and Vibration

Breakers, drills and saws can create significant noise and vibration.
The project may require:
  • Restricted working hours.
  • Low-impact tools.
  • Vibration monitoring.
  • Advance notification to occupants.
  • Protection of sensitive equipment.
  • Alternative cutting or drilling methods.
The lowest-disruption method should still be capable of exposing the required detail safely.

Water and Slurry Containment

Diamond drilling and cutting can produce water and slurry that may affect areas below or adjacent to the work.
The method should include:
  • Local collection rings.
  • Wet vacuums.
  • Protective sheeting.
  • Drainage and disposal arrangements.
  • Protection of services and finishes.
  • Monitoring of the opposite side.

What Should Cause the Work to Stop?

Stop conditions should be agreed before opening-up begins.
Work should normally stop if:
  • An unidentified service is encountered.
  • A tendon-like feature is found.
  • The construction differs significantly from drawings.
  • The approved opening dimensions are reached without exposing the required detail.
  • Unexpected cracking, movement or instability occurs.
  • Structural reinforcement is damaged.
  • Loose material extends beyond the planned area.
  • Hazardous material is suspected.
  • Water ingress or contamination cannot be controlled.
  • Temporary support appears inadequate.
The finding should be recorded and referred to the responsible engineer or authorised project representative.

What Measurements Should Be Recorded?

The required measurements depend on the technical objective.
Possible records include:
  • Opening length, width and depth.
  • Thickness of finishes and linings.
  • Structural element dimensions.
  • Concrete cover and bar diameter.
  • Reinforcement spacing and layers.
  • Steel-section dimensions.
  • Plate, bolt and weld dimensions.
  • Bearing lengths.
  • Wall and cavity thicknesses.
  • Timber section sizes and spacing.
  • Anchor diameter and embedment.
  • Foundation width, depth and founding level.
  • Crack width or visible section loss.
Measurements should be taken from identified reference points and supported by photographs or sketches.

How Should Construction Layers Be Recorded?

Where an opening passes through several materials, the report should record the order and thickness of each layer.
For example:
  • Floor finish.
  • Screed.
  • Membrane.
  • Insulation.
  • Structural slab.
  • Ceiling void.
  • Fire or acoustic lining.
A photograph with a scale and annotated layer boundaries can be more useful than a brief written description alone.

Photographic Records

A useful photographic sequence includes:
  • A general view of the room, elevation or structural area.
  • The marked opening location before work.
  • Scanning and service-detection markings.
  • Each major layer during removal.
  • The fully exposed structural detail.
  • Measurements with a visible scale.
  • Unexpected defects or construction.
  • The temporary making-safe arrangement.
  • The completed reinstatement.
Close photographs should be supported by wider views so the opening can be relocated accurately.

Unique Opening References

Each opening should have a unique reference used consistently on:
  • Plans.
  • Site markings.
  • Photographs.
  • Sample labels.
  • Measurement schedules.
  • Laboratory submissions.
  • The final report.
Revised or relocated openings should be recorded clearly rather than silently replacing the original reference.

Samples Taken During Opening-Up

Opening-up may produce concrete, mortar, steel, timber, insulation or coating samples for testing.
Each sample should record:
  • A unique sample reference.
  • The corresponding opening reference.
  • The exact location and depth.
  • Orientation where relevant.
  • Date of collection.
  • Condition and dimensions.
  • Requested laboratory tests.
  • Packaging and transport arrangements.
Poor sample traceability can make an otherwise valid laboratory result unusable.

Reinstatement After Structural Opening-Up

Reinstatement should be planned before the opening is formed.
The project should confirm whether the opening will be:
  • Repaired immediately.
  • Left open for engineer inspection.
  • Made temporarily safe.
  • Reinstated by another contractor.
  • Incorporated into later construction work.

What Performance Must Be Restored?

The repair may need to restore:
  • Structural integrity.
  • Concrete cover and durability.
  • Fire resistance.
  • Acoustic separation.
  • Weatherproofing.
  • Waterproofing.
  • Air tightness.
  • Thermal performance.
  • Security.
  • Surface appearance.
A cosmetic patch may not restore the original performance of the opened construction.

Concrete Reinstatement

A concrete repair may require:
  • Removal of loose concrete.
  • Preparation of sound repair edges.
  • Cleaning of reinforcement.
  • Corrosion treatment where specified.
  • Substrate preparation.
  • Compatible repair mortar.
  • Compaction and finishing.
  • Curing and protection.
  • Reinstatement of coatings and finishes.
The material and method should be specified for the opening geometry, orientation and exposure condition.

Fire-Protection Reinstatement

Where fire-protection boards, sprays, encasement or cavity barriers are removed, reinstatement should use an appropriate compatible system.
The record may need to identify:
  • The product used.
  • The installed thickness.
  • Fixings and joints.
  • Substrate preparation.
  • Installer details.
  • Inspection or certification.

Temporary Making-Safe

Where permanent reinstatement is delayed, temporary protection may include:
  • Rigid covers.
  • Barriers and exclusion zones.
  • Temporary weatherproofing.
  • Temporary fire stopping.
  • Edge protection.
  • Warning labels.
  • Daily inspection arrangements.
Temporary measures should not be recorded as permanent completion.

Who Is Responsible for Reinstatement?

Responsibility should be stated clearly in the investigation brief and quotation.
Possible arrangements include:
  • The investigation contractor completes all repairs.
  • The investigation contractor makes openings safe only.
  • A specialist repair contractor completes structural reinstatement.
  • The principal contractor reinstates finishes.
  • A façade or fire-stopping specialist completes specialist repairs.
Responsibility for decoration, waterproofing, fire protection and architectural finishes should not be assumed.

What Should an Opening-Up Report Include?

  • Project name, address and report reference.
  • Client and instructing party.
  • Purpose of the investigation.
  • Documents and drawings reviewed.
  • Unique opening references.
  • Level, grid and exact location.
  • Opening dimensions and depth.
  • Methods and equipment.
  • Scanning and service checks completed.
  • Materials and layers removed.
  • Exposed structural construction.
  • Measurements and condition observations.
  • Samples taken.
  • Differences from drawings.
  • Unexpected findings.
  • Photographs and annotated sketches.
  • Engineer inspection status.
  • Temporary making-safe or permanent repair.
  • Limitations and further recommendations.

Measured Evidence Versus Engineering Interpretation

Evidence Type Example
Observed A steel beam end and bolted plate were exposed.
Measured The exposed end plate measured approximately 12 mm thick.
Compared The observed connection differed from the cleated detail shown on the drawing.
Assessed The connection requires strengthening for the proposed load.
The investigation team should record the exposed evidence. The responsible structural engineer should determine its significance.

How Should Unexpected Findings Be Reported?

Unexpected findings should be recorded clearly rather than described only in informal site communication.
The record should include:
  • The opening reference.
  • The time and stage at which the finding occurred.
  • Photographs.
  • Measurements.
  • The action taken to stop or make safe.
  • The person notified.
  • The instruction received before work resumed.

Structural Opening-Up Within a Wider Investigation

Opening-up is usually one part of a wider evidence process.
The overall investigation may include:
  • Document review.
  • Visual surveys.
  • Dimensional surveys.
  • Concrete scanning.
  • Cover surveys.
  • Opening-up works.
  • Concrete cores.
  • Material testing.
  • Crack monitoring.
  • Structural calculations.
Opening-up should target the uncertainties that cannot be resolved adequately through less disruptive methods.

Limitations of Structural Opening-Up Works

Opening-up provides direct evidence but only at the exposed location.
Important limitations include:
  • Construction may vary elsewhere.
  • The opening may not expose the full connection or reinforcement detail.
  • Access may restrict the viewing angle.
  • Some layers may remain concealed for structural or safety reasons.
  • Hazardous materials may limit the investigation.
  • Immediate reinstatement may prevent later reinspection.
  • One sample may not represent a whole material phase.
  • Condition outside the opening remains unknown.
The report should explain where the findings apply and whether further locations are required.

Can One Opening Represent the Whole Building?

Not automatically. One opening confirms the construction at one local position.
Representativeness depends on:
  • Consistency of drawings.
  • Repeated non-destructive survey patterns.
  • Construction phases.
  • Previous alterations.
  • Position within the structural system.
  • Differences between perimeter, support and typical zones.
  • Variation in visible condition.
The structural engineer should determine whether additional openings are required.

What Opening-Up Cannot Confirm Alone

Opening-up does not automatically establish:
  • Structural capacity.
  • Material strength across the whole structure.
  • Continuity outside the opened area.
  • Condition of all concealed components.
  • Compliance across untested areas.
  • Suitability of a proposed alteration.
  • The remaining life of the structure.
These conclusions require engineering assessment and, where necessary, additional testing.

Common Structural Opening-Up Mistakes

Mistake Why It Is a Problem Better Approach
No defined engineering question. The opening may not expose the required detail. State exactly what must be verified.
Opening selected only for convenience. The location may not be structurally representative. Select representative and critical locations.
No approved opening dimensions. Too much or too little material may be removed. Define width, length, depth and stop conditions.
No scanning before concrete removal. Reinforcement, tendons or services may be damaged. Review drawings, scan and apply permit controls.
Exposing only the member rather than the connection. The load-transfer detail remains unknown. Define all connection components that must be visible.
Continuing after unexpected construction is found. The method may become unsafe or technically invalid. Stop, record and obtain review.
No contextual photographs. The finding may not be traceable later. Use general views, plans, references and close measurements.
Reinstating before engineer inspection. The required evidence may be concealed too early. Agree inspection and closure hold points.
Using a cosmetic patch only. Structural, fire, acoustic or weather performance may not be restored. Use a specified compatible reinstatement system.
Applying one result to the whole structure. Construction may vary between locations. Assess representativeness and state limitations.

Structural Opening-Up Works Checklist

  • Engineering objective: state exactly what must be exposed and confirmed.
  • Responsible engineer: identify who specifies and assesses the findings.
  • Location: provide level, grid, elevation and unique opening reference.
  • Drawings: provide structural, architectural, services and façade information.
  • Opening dimensions: define width, height, diameter and maximum depth.
  • Construction layers: identify finishes and materials expected to be removed.
  • Scanning: locate reinforcement, tendons and possible services.
  • Service controls: provide drawings, detection and isolation information.
  • Post-tensioning: confirm whether tendons are present or suspected.
  • Hazardous materials: review suitable intrusive survey information.
  • Structural stability: assess propping, support and removal sequence.
  • Access: define scaffold, MEWP, roof, floor or excavation arrangements.
  • Opposite side: identify occupied areas, falling-object and water risks.
  • Tools: select cutting, drilling and breaking equipment appropriate to the detail.
  • Dust and noise: define extraction, enclosure and working restrictions.
  • Stop conditions: state what happens if unexpected construction is encountered.
  • Measurements: list dimensions and condition observations required.
  • Samples: define quantities, references and laboratory tests.
  • Photographs: require context, progress, measurements and final condition.
  • Engineer hold point: confirm whether inspection is required before closure.
  • Temporary making-safe: define protection where the opening remains exposed.
  • Reinstatement: specify structural, fire, acoustic and weather requirements.
  • Responsibility: identify who completes each stage of repair.
  • Reporting: define plans, schedules, photographs and issue requirements.

Evidence-Based Summary

Structural opening-up works expose concealed building construction so it can be inspected, measured and recorded directly.
They may involve concrete breakouts, steel connection exposure, masonry openings, timber investigations, façade removals, inspection holes or foundation trial pits.
Every opening should answer a defined engineering question and have an approved location, size, depth and removal sequence.
Drawings, scanning, service detection, post-tensioning information and hazardous-material records should be reviewed before intrusive work.
Unexpected construction should trigger a stop-and-review process rather than uncontrolled enlargement of the opening.
Opening-up provides direct evidence at the exposed location but should not automatically be assumed to represent the whole structure.
The strongest opening-up investigations combine precise planning, project-specific RAMS, traceable measurements, engineer inspection and an agreed reinstatement strategy.

FAQ: Structural Opening-Up Works

What are structural opening-up works?
They are controlled intrusive works that remove finishes or materials to expose concealed structural construction for inspection and measurement.
Why are opening-up works required?
They are required where drawings, visual inspection or non-destructive surveys cannot confirm an important concealed detail with sufficient confidence.
Who specifies a structural opening?
The responsible structural engineer or designer should normally specify or approve the location, dimensions, depth and information required.
Should concrete be scanned before opening-up?
Normally, yes. Scanning helps locate reinforcement, tendons, services and congested areas before drilling or breaking begins.
What can a structural opening expose?
It may expose reinforcement, steel connections, masonry construction, timber bearings, façade brackets, anchors, cavity barriers, foundations or concealed services.
How large should an opening be?
It should be large enough to expose the required detail but no larger than necessary. The dimensions should be agreed before work begins.
Can an opening be enlarged on site?
It should not be enlarged beyond the approved limits without review and authorisation from the responsible engineer or project representative.
Can reinforcement be cut during opening-up?
Reinforcement should not be cut unless the responsible structural engineer has specifically assessed and authorised it.
Can opening-up be carried out in post-tensioned concrete?
Only with appropriate drawings, scanning and structural or post-tensioning specialist approval. Tendon-like responses should be treated as restricted areas.
Do opening-up works require RAMS?
Yes. The RAMS should address the exact location, method, tools, services, tendons, structural risks, access, dust, debris, stop conditions and reinstatement.
What happens if unexpected construction is found?
Work should stop at the agreed safe point, the condition should be recorded and the responsible engineer should review the next step.
Do openings need to remain available for inspection?
Some openings should remain exposed until the engineer has inspected the detail or confirmed that photographs and measurements are sufficient.
Do structural openings need to be repaired?
Normally, yes. Reinstatement may need to restore structural, fire, acoustic, waterproofing, thermal and durability performance.
Can ordinary filler be used for reinstatement?
Not necessarily. The repair material and system should be compatible with the original construction and the performance that must be restored.
Can one opening represent an entire building?
Not automatically. One opening confirms the construction at its local position. Additional openings may be required where construction varies.
What should an opening-up report include?
It should include the purpose, exact location, opening dimensions, methods, measurements, exposed construction, photographs, unexpected findings, reinstatement status and limitations.
Does opening-up confirm structural capacity?
Opening-up provides physical evidence. The responsible structural engineer must use that evidence with calculations and loading information to assess capacity.

Source Context and Editorial Note

This article is a STRUCTinspect technical explainer covering structural opening-up works used to expose concealed construction within existing buildings and structures.
It provides general construction information rather than a project-specific opening-up specification. Locations, dimensions, methods, access, temporary works, measurements, samples and reinstatement should be selected for the particular structure and engineering objective.
This article does not provide structural engineering, temporary works, post-tensioning, hazardous-material, fire-safety, health and safety, contractual or construction advice. Opening-up works should be specified, reviewed and interpreted by the appropriate structural engineer, designer, specialist contractor or competent professional responsible for the works.