A structural load takedown traces every gravity load from where it is applied, the floor and roof slabs, down through the beams, columns and walls that carry it, to the foundation. You do it in five steps: set the floor loads, find each support’s tributary area, turn area into load, accumulate the loads floor by floor, then apply a code load combination. StructLoads runs this whole sequence in the browser from a plan you draw, and the method below is the same whether you work it by hand or on screen.
What a load takedown actually computes
A gravity load starts as a pressure on a floor and ends as a reaction on a footing. The takedown is the arithmetic that follows that route, the load path, and reports how much load each support carries. Engineers run it early, as a sanity check on a scheme, long before a full analysis model exists. It is a standard early move in structural design practice, because it answers the questions that decide member sizes: how big is this column, and how heavy is this footing. There are two routes to the same reactions: the tributary area method used here, and summing beam support reactions after analysing every beam; Structville’s column load analysis notes the tributary route is the popular one for its simplicity and speed, while the beam-reaction route picks up continuous-beam effects and wall loads at the cost of a full beam analysis first.
Keep two things separate in your head and the whole exercise stays clean: the floor pressure (your dead, live and roof loads in kN/m2 or psf) and the geometry (the area each support drains). Multiply one by the other and you have load.
The five steps of a gravity load takedown
Set the loads first, resolve the geometry second, then accumulate and combine.
| Step | What you do | What it produces |
|---|---|---|
| 1. Set loads | List the dead, live and roof loads for each level, including slab self weight | Pressures in kN/m2 |
| 2. Tributary area | Find the slice of floor nearest each support | An area in m2 per support |
| 3. Area to load | Multiply each tributary area by the floor pressure | Load per support per level |
| 4. Accumulate | Carry loads from the top level down, adding each floor | Cumulative load per support |
| 5. Combine | Apply the governing code load combination | Factored design reaction |
The first three steps happen on every floor. The last two stitch the floors together into the reaction that sizes the column and the footing.
How do you find each support’s tributary area?
A support’s tributary area is the part of the floor closest to it, bounded by the lines drawn halfway to the neighbouring supports. On a regular grid those lines sit at the half bays, so an interior column carries a full bay, an edge column about half, and a corner column about a quarter. On irregular or L-shaped floors the halfway lines stop being obvious, which is where hand sketches drift. The full method, and where it breaks, is covered in how tributary areas actually work.
How do loads stack through multiple floors?
Walk down the support carrying a running total. At the roof, the column gathers the roof load over its tributary area. One floor down, it gathers that floor’s load and adds the reaction from above. By the foundation it holds everything stacked on it. A three storey interior column on a six metre by five metre grid, with 4.5 kN/m2 dead and 3.0 kN/m2 live per floor, gathers roughly 519 kN dead and 270 kN live before any factors. The full arithmetic is set out in a floor-by-floor worked example.
Which load combination sizes the support?
Service loads do not size members; factored loads do. You combine the accumulated dead, live and roof loads with the factors from your code. Under ASCE 7 the usual gravity combinations are 1.4 times dead, and 1.2 times dead plus 1.6 times live plus 0.5 times roof. The largest result governs. For a column that supports a large accumulated area, the code also lets you reduce the design live load, as explained in ASCE 7 live load reduction.
How do you check a load takedown is right?
Three quick checks catch most errors. First, the area balance: the tributary areas of all supports on a floor should add up to the floor area, with nothing counted twice or lost. Second, the ratios: an interior column should carry roughly twice an edge column and four times a corner, so an outlier is a flag. Third, the total: the sum of all support loads on a floor should equal the floor pressure times the floor area. If those three agree, the geometry and the arithmetic are consistent.
Key takeaways: the load takedown
A load takedown is five repeatable moves: pressures, tributary areas, area to load, accumulate, combine. The arithmetic is easy; the geometry and the bookkeeping are where errors hide, which is exactly the part StructLoads automates by drawing the tributary partition and keeping the running totals for every support at once. Use it for the early scheme, then hand the numbers to a qualified engineer for the detailed design.
Related guides
More in this series: the multi-storey load takedown and what a load path is. It also connects to what a transfer beam is.
Quick answers
How do you do a structural load takedown?
Set the dead, live and roof loads on each floor, find every support’s tributary area, multiply area by load, accumulate the loads from the top floor down to the foundation, then apply a code load combination. The result is the factored reaction at each column, wall and footing. StructLoads runs these five steps from a plan you draw.
What is the difference between a load path and a load takedown?
The load path is the route a load follows from the slab through beams, columns and walls to the ground. The load takedown is the calculation that adds the load up along that path. You trace the path to see where load goes, then take it down to get the number at each support.
Do you work a load takedown top down or bottom up?
Top down. Start at the roof, compute the reactions, carry them to the level below, add that floor’s own load, and repeat to the foundation. Working downward means each reaction already includes everything carried from above, so the foundation load is the running total.
When is a hand load takedown not enough?
A hand takedown is a preliminary check, not a final design. Once framing is irregular, two-way action matters, or you need member capacity, deflection and lateral effects, move to a full analysis model. The takedown sizes the early scheme, and a qualified engineer must review the result.