Most design software tells you what it can do. This page is the other half, and it is here because a tool that hides its edges is more dangerous than one that has fewer features. Nothing below is a roadmap item being coy — each one is a case where producing a plausible-looking answer would be worse than producing none.
A PASS is not approval
A PASS means the design checks out for the loads you entered, under the assumptions printed on the sheet. It does not mean the building is safe to build, that the loads were the right loads, or that the structural scheme makes sense. Structura is a preliminary design tool and assumes a reviewing engineer — you — who reads the sheet and takes responsibility for it.
Every output carries that disclaimer, and it is agreed to at sign-in rather than buried. See the terms of use.
No seismic design
There is no earthquake load case, no ductility detailing and no capacity design. For most of Nigeria that is the normal engineering position; if your project sits somewhere it is not, this is not the tool for it.
No piles, and no settlement
Foundations go as far as pad, strip and raft. There is no pile module, because piling needs a soil model — layer profile, SPT or CPT data, skin friction and end bearing — that this app does not ask for and should not pretend to infer. When a raft cannot carry the building, that is where the engine stops and hands the problem back.
Settlement is not calculated either, for any foundation type. Bearing pressure is checked against the allowable value you supply, which is a different question from how much the building will move.
Wind is a simplified static method
Uniform pressure over the height, a net windward-plus-leeward coefficient, no terrain or height profile and no dynamic response. It was chosen over a half-remembered BS 6399-2 table on purpose: inventing code coefficients would be worse than a clearly labelled simplification.
You supply the wind speed, and it is used as an effective gust speed at roof level — it must already include terrain and height, and only an altitude factor is applied on top. There is no Nigerian wind map built in.
The height ceilings, and why they are where they are
| Path | Limit | What sets it |
|---|---|---|
| Gravity only | 4 storeys | No lateral load is considered at all, so above this a clean PASS would be misleading |
| Wind, braced walls or core | 8 storeys | Beyond this needs dynamic wind and a proper stiffness analysis |
| Wind, moment frame | 8 storeys | Same |
These are safety boundaries, not licensing tiers. The engine refuses rather than warns, and the pricing is deliberately arranged so that nobody can save money by describing their building as shorter than it is.
A building that steps in is gravity-only
Columns may stop below the top of the building, so a first floor can set back off the ground floor. What cannot follow is wind: the lateral method applies one pressure over the full height to one plan extent, resisted by the frames of one layout — and a setback changes the exposed face, the frames and the lever arm at every level.
So a stepped building is designed for gravity alone, which caps it at 4 storeys like any other gravity-only design. It is refused outright rather than warned about, because there is no version of "roughly right" available: either the building is analysed storey by storey, or it is not analysed for wind at all. Carry the columns full height and the wind paths are open again.
No transfer beams
A column that stops while the floor above still spans over it is carried by a transfer beam, and there is no transfer element in this engine — it would design that beam as an ordinary span and print PASS on it. That layout is refused, naming the column: carry it up, or set the storey above back so nothing lands on its head.
This is the same rule from the other side as the setback above. Stopping a column where the building has stopped with it is a setback; stopping one under a floor that keeps going is a transfer, and only one of the two is designed here.
An open node is covered conservatively, not analysed
Take a column out and the beam over it spans the whole way, which the engine designs. What it does not calculate is how a two-way slab really redistributes around a missing support, or how two beams crossing over an empty node share the load. Instead each neighbour is designed for the whole of the widened strip, so their tributary areas overlap and add to more than the plan area — the overview reports that percentage rather than hiding it, because under-counting is the dangerous direction. Check the redistribution by analysis before building to it.
Beam-column joints are not designed
Deliberately not faked. BS 8110 has no joint calculation for non-seismic frames of this type — it is a detailing matter, and the sheets defer it along with laps and anchorages rather than inventing a check to look thorough.
Schedules and fire cover need confirming
Bar bending schedules are produced to BS 8666, but the anchorage and lap assumptions behind them are simplified. They are stated on the sheet, and they are for you to confirm at detailing.
Fire figures are the tabulated ones for dense concrete fully exposed. The real requirement depends on occupancy, aggregate and how many faces are exposed — none of which the app knows — so every sheet that uses them says to confirm.
What it is not, in one line
Not a finite-element package, not a code-compliance certificate, and not a replacement for judgement. It is the takedown and the member design you would otherwise do by hand, done consistently and shown step by step, so the time goes into checking rather than arithmetic.
Within those limits, it is free to try
Single members — slab, beam, column, footing, stair, lintel — run free in the browser, with nothing to install. Where the engine cannot design what you are describing, it says so rather than returning a number.
Open Structura in your browser
On Android, get it on Google Play; on iPhone and iPad, get it on the App Store — same account as the browser.
Read next
- What Structura designs — every member, and the checks each one runs
- How it works — what a calc sheet contains
- Worked examples — the calculations done by hand, step by step
- Soil bearing capacity — where the bearing pressure comes from, and where pads give way to a raft and then to piles