Structural calculations turn a design idea into something buildable
Any work involving load-bearing walls, new openings or altered roof structures needs proper structural design before it reaches site.
A structural engineer works out how loads travel through a building and specifies what is needed, such as a steel beam of a particular size, to safely carry those loads once a wall is removed or an opening formed. This is not a step to skip, even on work that looks straightforward, because the consequences of getting it wrong range from cracking and sagging to genuinely dangerous structural failure.
Structural calculations and drawings are usually required as part of a Building Regulations submission for anything involving load-bearing alterations, new steelwork, altered roof structures, or foundations affected by ground conditions. Building control will not sign off this kind of work without evidence that a competent person has designed it properly.
On a typical extension or loft conversion, the structural engineer's drawings sit alongside the architectural design, and the two need to be consistent, since a beautifully drawn kitchen extension is no use if the structural engineer specifies a beam depth that clashes with the ceiling height shown on the architect's plans.
When an engineer is needed
Removing or altering a load-bearing wall, forming a new opening for bifold doors or a wider kitchen archway, converting a loft where new floor loading and roof alterations are involved, and any extension with new foundations near existing structure or on sloping or uncertain ground all typically need engineering input.
Even seemingly simple jobs like enlarging a window opening in a solid wall can need a structural check if the wall carries load from above, which is worth confirming before assuming a job is purely cosmetic.
What the drawings actually specify
Structural drawings typically detail beam sizes and types, padstones or bearing points, foundation depths and reinforcement where needed, and any temporary support required while work is carried out, such as propping a wall while a beam is installed underneath it.
These details feed directly into what materials get ordered and how the site sequence is planned, since a steel beam has to be delivered and lifted into place at exactly the right stage of the build.
Ground conditions and foundations
Where ground conditions are uncertain, such as sloping sites, made ground, or proximity to trees that can affect clay soils through moisture changes, an engineer may recommend trial holes or specific foundation designs beyond a standard strip foundation. This is particularly relevant on some of the more varied ground found across South Hams and parts of rural Teignbridge.
Getting the foundation design right at this stage avoids costly problems later, since foundations are the hardest and most expensive part of a building to correct once covered over.
How this fits with the wider design team
On most projects the sequence runs from initial design, through planning if needed, to detailed architectural drawings, structural design, and then a Building Regulations submission incorporating both. We coordinate with whichever architect or designer and structural engineer are involved to make sure the drawings translate cleanly into a buildable, correctly sequenced site programme.
If a project does not already have a structural engineer involved, we can point clients towards ones we have worked with before, though the appointment and fee arrangement is between the client and the engineer directly.
Common questions
Can any builder just install a steel beam without an engineer?
No. The beam size and support detail need to be properly calculated for the loads involved, and building control will require evidence of this before signing off the work.
Does every extension need a structural engineer?
Most do, particularly where new openings, altered roof structures, or foundations near existing buildings are involved. Very simple like-for-like replacements sometimes need less, but it is always worth checking.
How does propping work while a wall opening is formed?
Temporary supports carry the load safely while the old wall is removed and the new beam installed, following the engineer's method statement, before the props are removed once the beam is properly bearing.
What if ground conditions turn out to be different once digging starts?
The engineer can revise the foundation design based on what is actually found on site, which is one reason foundation work sometimes needs a short pause for reassessment.
Tell us about the job and we’ll come back with a clear next step.
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- Planning permissionWhen planning permission applies, when it does not, and how Torbay, Teignbridge and South Hams differ.
- Building regulationsHow Building Regulations approval works, what inspections happen and how it differs from planning permission.
- Party wall agreementsHow the Party Wall Act works, when notice is needed and why a schedule of condition protects everyone.
- Choosing a builderHow to vet a builder properly, compare quotes fairly, and judge communication before work begins.