Structural engineer or building surveyor: which do you need?

The short answer

A building surveyor looks at the overall condition of a property, including the roof, damp, windows, services and general defects, and tells you what needs attention. A structural engineer focuses on whether the structure is sound, works out why it is moving or cracking, and designs how to repair or alter it. If you want a broad health check, start with a surveyor. If you have a specific structural concern or need calculations for building work, you need an engineer.

Many situations need both, one after the other. A surveyor spots a crack during a purchase survey, then recommends a structural engineer to establish the cause. That hand-off is normal and is how the system is meant to work.

What a building surveyor does

Chartered building surveyors are usually members of RICS. For homebuyers, their best-known product is the RICS home survey at Level 2 or Level 3. They walk the whole property, rate the condition of each element and flag defects, repairs and maintenance needs.

Surveyors are trained to recognise structural symptoms such as cracking, distortion and bulging walls. What they generally do not do is calculate loads, design beams or carry out a detailed investigation into why a building is moving. When a survey says a defect needs further investigation by a structural engineer, that is the surveyor working within their scope, not passing the buck.

Building surveyors also work on dilapidations, defect diagnosis in commercial property, and as party wall surveyors. Their breadth is the strength. A survey picks up the slipped slates, the failed flashing, the blocked gutter and the rising damp that an engineer would not be looking for, and those are the defects that most often cost homeowners money in the first few years.

What a structural engineer does

Structural engineers deal with how a building carries its loads down to the ground. Chartered engineers are typically members of the IStructE or the ICE. They inspect and diagnose structural defects, then design the solution with calculations and drawings that Building Control will accept.

That covers two broad types of work. The first is inspection: cracks, movement, bowing walls, sagging floors and roofs, and questions from lenders or insurers. The second is design: beams for knocked-through walls, extensions, loft conversions, basements, underpinning and repairs. An engineer's report goes deeper on the structure than a survey, but it will not comment on damp, windows, heating or decoration.

The key difference is diagnosis. Faced with a diagonal crack over a bay window, a surveyor will record it, rate it and recommend investigation. An engineer will look at the crack pattern, the age of the house, nearby trees, drain runs and the ground, then form a view on whether the movement is historic or ongoing, and what, if anything, needs doing. That opinion is what a lender, insurer or buyer usually wants when a structural question has been raised.

Building Control surveyors are different again

People often hear building surveyor and think of the Building Control surveyor who inspects their extension. That is a separate role. A Building Control surveyor, from the council or a private approver, checks that work complies with the Building Regulations. They review the engineer's calculations and inspect work on site, but they are not your adviser and they do not design anything.

So on a typical extension you might deal with three people with similar titles: a party wall surveyor handling notices with neighbours, a Building Control surveyor checking compliance, and a structural engineer designing the structure. Only the engineer produces the calculations.

Which one for common situations

As a rough guide, this is who to call first in the situations we see most often across London.

• Buying a house or flat: a building surveyor for a Level 2 or Level 3 survey, then an engineer if structural issues are flagged
• A crack that is new, wide or growing: a structural engineer
• Removing a wall, converting a loft or building an extension: a structural engineer for design
• Damp, rot or roof leaks: a building surveyor
• Neighbour's works affecting your home: a party wall surveyor, with an engineer reviewing the structural design if needed
• A lender or insurer asks for a structural report: a structural engineer

When you want both in one place

On a purchase, it can save time to have the survey and the structural opinion come from the same team, so the structural questions are answered rather than deferred. Our RICS Level 2 or Level 3 building survey includes structural engineer input on any significant defects found.

If the survey has already been done and flagged something, a General Structural Inspection report gives a focused view of the structure across the property. All our structural inspection reports are signed off by a chartered engineer who is a Member of the Institution of Civil Engineers (MICE). For help choosing between report types, see which structural inspection report you need.

Checking you have the right person

Whoever you appoint, ask what their qualification is, what the report will and will not cover, and who it is addressed to. A lender may need a report that names them or confirms they can rely on it. Read the exclusions section before you rely on any report, whether from a surveyor or an engineer, because that is where the limits of a visual inspection are set out.

Be clear about the question you need answering before you book. Is a crack serious? Can this wall come out? Will the lender accept the property? A focused question lets the right professional give a focused answer, and stops you paying for a broad report when a narrow one would have done, or the other way round. If you are buying, our guide to structural reports for a house purchase walks through when an engineer is worth adding to the survey.