Structural design revision or variation
Revisions to our structural design when the scheme changes, such as a new layout, different materials or site findings.
About this service
A structural design revision updates our calculations and drawings when your scheme changes after we have issued the design. Changes are normal. Architects refine layouts, clients rethink openings, builders find a better product and sites reveal surprises once the floor is up. A revision keeps the structural design consistent with what will actually be built, so Building Control and your builder are always working from the right information.
Revisions start from £150 + VAT, because they build on our original design rather than starting again. We review what has changed, recalculate the affected elements and reissue drawings with clear revision marks and notes. Small changes such as a different joist product or a moved opening are usually quick. Larger changes, such as a new roof form or an extra floor, may need a broader redesign, which we confirm before starting.
Every revision goes through the same three-step quality control process as the original design, with final sign-off by our Head of Engineering. We send revised calculations and drawings to Building Control and liaise with them on any queries. That matters because an unapproved substitution on site can lead to problems at completion, even when the alternative is perfectly adequate structurally.
When you need it
- Your architect has changed the design
- Site conditions differ from what was expected
- Your builder wants to use an alternative product
What's included
- Review of the changes
- Revised calculations
- Updated drawings
How it works
- Tell us what has changedSend revised architectural drawings, the builder's proposed alternative or photographs of site findings. We confirm the scope of the revision and a fixed fee in writing.
- Review the impactWe trace how the change affects the structure, from the element itself to the beams, walls and foundations that support it, so nothing downstream is missed.
- RecalculateAffected members, connections and foundations are recalculated, with any alternative products checked against the manufacturer's published data and against the assumptions in our original design.
- Reissue drawingsUpdated drawings are issued with revision letters, dates and clouded changes, so everyone on site can see exactly what is different from the previous issue.
- Update Building ControlWe send the revised information to Building Control and deal with their questions, keeping the approved design aligned with the work actually being built on site.
What you receive
Site changes and substitutions: why revisions should come first
The most common problems arise when changes happen on site without the engineer. A builder swaps a steel beam for a different size, moves a post or uses a different lintel because it is in stock. The alternative may be fine, or it may be undersized, poorly supported or missing a padstone. Either way, without revised calculations Building Control has no evidence it complies, which can delay sign-off. Our guide on steel beams and padstones shows how small details affect the design.
Site findings are the other big driver. Opening up may show foundations shallower than expected, joists running the other way, or a wall that is not what the drawings assumed. In those cases we review the evidence and revise quickly so work can continue. If the change is fundamental, such as moving from a single-storey to a two-storey scheme, a fresh extension structural package may be more appropriate, and we will say so before you commit.
Projects that used this service
Frequently asked questions
Can my builder use a different steel beam to the one specified?
Only if the engineer has checked and approved it. Beam size, grade, bearing length and padstones all affect whether a substitute works. A builder's alternative may be perfectly adequate, but it needs revised calculations and drawings so Building Control can approve it. Installing it without approval can delay completion and lead to expensive rework.
How much does it cost to change a structural design?
Our structural design revisions start from £150 + VAT for straightforward changes, such as a different product or a minor layout adjustment. Larger changes affecting several elements cost more. We review what has changed first and confirm a fixed fee in writing before starting work, so you know the cost before anything is revised.
Do revised structural drawings need to go back to Building Control?
Yes. Building Control should be working from the same structural information that is being built. If the design changes, revised calculations and drawings must be submitted so they can check compliance. We send revisions directly and deal with any queries, which helps avoid delays at inspections and completion.
Can you revise a structural design done by another engineer?
This service covers revisions to designs we have produced. If another engineer prepared the original, they are usually best placed to revise it. Where that is not possible, we can review their design and take on the affected elements, but that is normally treated as new design work with its own scope and fee.