A load takedown is only as trustworthy as the checks you run on it, and the useful ones take seconds. Four checks catch most errors: area balance, reaction ratios, total load, and units with equilibrium. If all four pass, the takedown is internally consistent. StructLoads shows the first two on screen as you work, and this page sets out how to run each and what a failure means.
Check 1: area balance
Area balance compares the sum of the tributary areas to the floor area. Every square metre of floor should drain to exactly one support, so the tributary areas should add up to the floor area, the property guaranteed by a clipped Voronoi diagram partition. A balance below one hundred percent means some floor is unsupported in the model; above it means an overlap. It is the single most useful geometry check, and StructLoads reports it as a live percentage.
Check 2: reaction ratios
On a regular grid the reactions should follow a known pattern: an interior column about twice an edge column and four times a corner, the one to one half to one quarter ratio from interior vs edge vs corner column loads. If an edge column comes out heavier than an interior one, or a corner is close to the interior, a support is misplaced or the outline is mis-drawn. The ratio check finds the single-coordinate slip that area balance can miss.
Check 3: total load
The total of all support loads on a floor should equal the floor pressure times the floor area. If the floor carries 7.5 kN per square metre over 200 square metres, the support loads should sum to 1500 kN. This confirms the load was applied correctly, not just that the geometry balances. A mismatch here, with area balance passing, points to a wrong pressure rather than a wrong area.
Check 4: units and equilibrium
The quiet errors are unit slips: mixing kPa with kN, or metres with millimetres. Confirm every input is in consistent units before trusting the output. Then apply the statics equilibrium check across the whole building: the total load arriving at the foundations should equal the total load applied on all the floors, because force is conserved on the way down. If the two totals differ, load has been lost or added somewhere in the stack.
The four checks at a glance
Run them in order; each catches a different class of error.
| Check | What it confirms | A failure means |
|---|---|---|
| Area balance | Geometry partitions the floor | A region lost or overlapped |
| Reaction ratios | Supports are placed sensibly | A misplaced support or outline |
| Total load | Loads applied correctly | A wrong floor pressure |
| Units and equilibrium | Consistent inputs, force conserved | A unit slip or lost load |
These are the same checks built into the workflow in how to do a load takedown fast and check it; this page is the detailed version of that closing step, which complements the full method in how to do a structural load takedown.
What the checks do not catch
The checks confirm internal consistency, not correct inputs. A takedown can balance perfectly and still be wrong if the floor loads, the occupancy class or the load combination are wrong. That gap matters more than it sounds: Ren, Terwel, Yang and van Gelder’s study of human factors in structural safety notes that failures trace to human error far more often than to technical causes, and cites Walker’s finding that errors in defining the design loads are the dominant error type, at 61 percent, which is precisely the input these four checks cannot validate. So the checks catch geometry and arithmetic slips, but a wrong load value or the wrong code passes straight through. That is why the checks are a first line, and a qualified engineer reviews the inputs and the governing code.
Key takeaways: checking a load takedown
Run four checks: area balance, reaction ratios, total load, and units with equilibrium. Together they confirm the takedown is internally consistent and catch the common geometry and typo errors. They do not validate the input loads or the code, which still need engineering review. StructLoads surfaces the geometry checks live so they are part of the workflow, not an afterthought.
Quick answers
How do you check a load takedown?
Run four checks. Area balance: the tributary areas should sum to the floor area. Reaction ratios: an interior column should be about twice an edge column and four times a corner. Total load: the sum of all support loads should equal the floor pressure times the floor area. Units and equilibrium: consistent units, and the total down equals the total applied.
What is the area-balance check?
Area balance compares the sum of the tributary areas to the actual floor area. If they match, every square metre is assigned to exactly one support, nothing double counted or lost. A balance below one hundred percent means some floor is unsupported in the model; above it means an overlap. It is the single most useful geometry check.
What does a wrong reaction ratio tell you?
It points to a geometry error. On a regular grid an interior column should carry about twice an edge column and four times a corner. If an edge column comes out heavier than an interior one, or a corner is close to the interior, a support is likely misplaced or the outline is mis-drawn. The ratio check finds single-coordinate mistakes fast.
Can a load takedown pass the checks and still be wrong?
Yes. The checks confirm internal consistency, not correct inputs. If the floor loads, the occupancy classification or the load combination are wrong, the takedown can balance perfectly and still be unsafe. The checks catch geometry and arithmetic slips; they do not catch a wrong load value or code, which is why a qualified engineer reviews the inputs too.