# The site store and waste: where the material you actually bought goes

> Material that is bought and never becomes finished work is a silent loss. The five causes of overconsumption and how to tell them apart in time.

- Author: Felipe Arancibia — Sr. Product Designer
- Published: 2026-09-03
- Original: https://usepaladio.com/en/blog/almacen-desperdicio-material-obra/
- Costs

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Material waste is the gap between what was consumed and what the work actually executed required. It is one of the largest and least visible losses on a project, because it shows up in no report: the material was bought, it was paid for, it came onto the site, and it simply never turned into finished work.

Unlike low output, which shows up in progress, overconsumption shows up in nothing. It appears in the final result, when there is nothing left to do about it.

## The five causes, and each one is fixed differently

This is the most important part of the article. "Overconsumption" is not a diagnosis: it is five different problems producing the same symptom.

| Cause | How you spot it | How you attack it |
|---|---|---|
| **Process waste** | Offcuts, leftovers, normal losses | Method, modulation, optimised cutting |
| **Rework** | Something already built was redone | Quality, supervision, technical information |
| **Damage in storage** | Material damaged, set hard, rusted | Storage and rotation |
| **Theft or diversion** | Missing with no technical explanation | Access control, custody, counting |
| **Budget error** | The theoretical consumption was wrong | Fix the schedule of rates for next time |

Confusing them is the expensive mistake. A director who assumes theft when the problem is rework will post a guard and damage the relationship with the team while the real problem carries on.

**The way to tell them apart is chronological.** Process waste is even and constant. Rework appears in spikes, tied to specific dates. Damage concentrates in sensitive materials and in certain seasons. Theft tends to come in steps and in materials that are easy to resell. A budget error is a constant deviation from day one.

Without a dated record of consumption, all five look the same.

## The basic calculation

You do not need an inventory system. You need this comparison, for the four or five materials that carry the most weight:

```
Theoretical consumption = quantity executed × unit consumption from the budget
Overconsumption         = actual consumption − theoretical consumption
```

With a concrete block example:

| Item | Value |
|---|---|
| Wall built and verified | 420 m² |
| Unit consumption from the budget | 12.5 units/m² |
| Waste allowed in the budget | 3 % |
| **Theoretical consumption including waste** | **5,408 units** |
| Actual consumption recorded | 5,940 units |
| **Overconsumption** | **532 units · 9.8 %** |

That extra 9.8 % on top of the waste already allowed for is a number you can investigate. Without the comparison, it is 532 blocks nobody will ever miss.

**The key to the calculation is that the quantity executed has to be reliable.** If progress is badly measured, theoretical consumption is wrong, and the apparent overconsumption may be a measurement error rather than a material problem.

## The materials worth the effort

Controlling everything does not pay for itself. Control the ones that meet two of these three conditions:

- They account for more than 5 % of the materials budget
- They have a high unit value or are easy to resell
- They are vulnerable to damage in storage

On a traditional project that usually comes down to: steel, cement, block or brick, and the higher-value finishes. Five well-controlled materials capture most of the loss there is to capture.

## The site store, without building an operation

Four practices, none of which needs a system.

**One entry point and one person responsible.** Every material that comes in is received, counted and recorded against the purchase order. Without this, any other control is decorative.

**Issues against a work face.** Material should leave the store assigned to an identifiable work face or budget item. That is what later lets you compare consumption against execution of that item. With no assignment, consumption is a useless global total.

**Storage suited to the material.** Cement on pallets and under cover, oldest out first. Steel off the ground. Block stacked to a sensible height. It is boring and it prevents most of the damage.

**Periodic counts of the critical five.** Not a full inventory: a count of five materials, every fortnight. Half an hour, and it catches drift while it is still small.

## Where it really leaks

Four points that come up again and again:

**Between receipt and the work face.** Material that arrived, was unloaded wherever there was room, and got damaged or lost in the internal haul.

**At the cut.** Pieces cut with no planning for yield. In materials that come in standard lengths, the difference between cutting to a plan and cutting as you go can be 10 % of consumption.

**In rework.** It is the most expensive cause of overconsumption because it pays twice: the material lost and the labour to redo it. And it is the one least often recorded as such.

**In the leftovers at close-out.** Material bought in excess that nobody returned and nobody moved to another project. In companies running several projects, it is an entirely avoidable loss if somebody keeps the record.

## What makes all of it possible

Everything above rests on two records you should probably have already:

- **Quantity executed per budget item**, measured the day it is executed
- **Material in and material out**, assigned to a work face

With those two, overconsumption calculates itself and comes with a date, which is what lets you tell the five causes apart. Without them, overconsumption shows up in the final result as a number with no explanation, and by then there is nothing left to investigate.

## Frequently asked questions

**How much waste is normal?**

It depends on the material and the building system, and you are better off using the percentages from your own history than the ones in the manual. What matters is not the absolute level but the deviation from what you budgeted.

**Is a dedicated storekeeper worth it?**

On mid-sized projects, almost always. The cost of the position is usually less than the overconsumption it prevents, plus the days lost to material that is on site but not at the work face.

**How do I tell theft from waste without accusing anyone?**

By the time pattern and the type of material. Overconsumption spread evenly across every material is process waste. Overconsumption concentrated in easily resold materials, in steps, is something else. The objective figure spares you the uncomfortable conversation built on suspicion.

**Can waste be charged to the client?**

Budgeted waste is already inside the unit price. Anything beyond it is yours, unless it stems from a cause attributable to the client —design changes, late information— and was documented at the time.

**Is it worth controlling material on a lump sum project?**

It is worth more, because there nobody forces you to measure and the overconsumption comes straight out of your margin. It is precisely the system where least is controlled and where not doing it costs most.