Understanding Structural Surveys and Appraisals

The three things people mean by 'survey'

The critical distinction is scope. A surveyor assesses the condition of the building. An engineer assesses the behaviour and adequacy of its structure. A surveyor who finds structural movement will usually recommend that a structural engineer is consulted — that recommendation is the trigger for an appraisal, not a duplication of it.

• —Homebuyer report or condition report — a chartered surveyor's overview of a property's general condition for a purchaser, using a traffic-light style rating. Broad, non-intrusive, and not a structural analysis.
• —Building survey (formerly full structural survey) — a chartered surveyor's detailed inspection of the whole property, covering condition, defects, materials and maintenance. Wider in scope, still not an engineering assessment.
• —Structural inspection and appraisal — a structural engineer's assessment of a specific structural question: is this crack significant, can this floor carry this load, is this wall stable, what caused this movement.

When a structural engineer is the right appointment

• —Cracking has been noticed, has changed, or has been flagged in a survey or mortgage valuation
• —Floors are sloping or bouncing, or doors and windows have begun to bind
• —A wall is bulging, leaning or has separated from a floor or roof
• —A lintel or beam is visibly deflecting, or a chimney breast has been removed without support
• —A change of use will increase loading — storage, plant, gym equipment, occupancy
• —Insurers, lenders or building control have asked for a structural engineer's opinion
• —Alterations are planned and the capacity of existing structure needs establishing

What happens during a structural appraisal

The engineer starts with desk information: drawings if any exist, the age and construction type of the building, previous reports, and the history of the issue. On site, the inspection is visual and non-intrusive unless opening up has been arranged in advance.

The engineer records the form of construction, the load paths, the nature and pattern of any cracking, dimensions, deflections, moisture and drainage evidence, and the influence of trees, ground conditions and neighbouring works. Crack widths are measured rather than described, because width and pattern are what distinguish shrinkage from movement.

Diagnosis follows from evidence. Where a cause cannot be established from a single visit, the honest answer is monitoring or investigation rather than a confident but unsupported conclusion.

Visual, intrusive and monitored assessment

• —Visual inspection — the usual starting point, covering what can be seen without damage
• —Opening up — lifting floorboards, removing plaster or forming trial holes to confirm construction
• —Trial pits — excavation to establish foundation depth and type, and the ground beneath
• —Monitoring — crack gauges, telltales or level surveys over months to establish whether movement is progressive or dormant
• —Material testing — where the strength or condition of concrete, steel or timber must be established
• —Specialist input — drainage surveys, arboricultural assessment or soil investigation where those are the likely cause

What a structural appraisal report contains

A useful report is unambiguous about significance. 'Not structurally significant, no remedial work required' is a legitimate and frequently correct conclusion, and it is often precisely what a purchaser, lender or insurer needs in writing.

• —The instruction and the specific question the report answers
• —The scope, extent and limitations of the inspection, including what was not accessible
• —A description of the building and its structural form
• —Observations, with locations, dimensions and photographs
• —Engineering assessment and the most likely cause of any defect
• —Conclusions on structural significance and urgency
• —Recommendations — no action, monitoring, further investigation, repair or remedial design
• —Any exclusions, such as drainage, damp, timber decay or asbestos

Limitations you should expect

No visual inspection can confirm what is concealed. Foundations, wall ties, embedded steelwork, reinforcement and the condition of buried drainage are not visible, and an engineer who claims certainty about them from a walk-round is overstating the evidence.

Reports are also prepared for a specific client, purpose and date. They should not be relied upon by a third party or reused years later without being revisited, because the building and its context change.

Cracking, subsidence and insurance

Where subsidence is suspected, the insurer of the property usually leads the process and appoints its own loss adjuster and engineer. An independent appraisal is still valuable, particularly for establishing whether a claim is appropriate, or for assessing a property before purchase.

Most cracking, however, is not subsidence. Thermal movement, shrinkage, sulphate attack, wall tie corrosion, lintel deflection, roof spread and simple settlement of made ground all produce cracking, and each has a different pattern, distribution and remedy.

Preparing for the inspection

• —Clear access to affected areas, cellars, roof spaces and external elevations
• —Any drawings, previous reports, monitoring records or guarantees
• —A short history: when the cracking appeared, whether it has changed, and what has been done
• —Dates of previous alterations, extensions or underpinning
• —Information on trees, drainage, neighbouring works and any past flooding or leaks
• —Photographs of anything that has since been decorated over

Related guidance

• BES-TG-003Understanding Cracks in BuildingsRead →
• BES-TG-004Preparing for a Structural InspectionRead →
• BES-TG-010Foundations for Building Alterations and ExtensionsRead →
• FAQDo I need a structural survey?Read →
• FAQWhat is a structural appraisal?Read →
• FAQWhat happens during a structural inspection?Read →
• FAQShould I be worried about structural cracks?Read →