architect-fees-be

Belgian architect fee calculator based on official methodology. Calculate professional fees (honoraires) from surface area and construction costs.

Installation

npm install architect-fees-be
# or
pnpm add architect-fees-be
# or
yarn add architect-fees-be

Quick Start

import { calculateHonoraires } from 'architect-fees-be';

// Calculate fees for a 2300m² renovation project costing €3,000,000
const result = calculateHonoraires(2300, 3_000_000);

console.log(result.honoraireMoyen); // ~214,860€
console.log(result.averageHours);   // 3581 hours

How It Works

The calculator uses a dual-approach methodology:

1. Surface-based estimation: Calculates hours based on building area
2. Cost-based estimation: Calculates hours based on construction budget

The final fee is the average of both approaches, multiplied by an hourly rate.

Formula

Hours per m² = c × surface^d
Hours from surface = surface × hoursPerM²

Hours per €10,000 = e × cost^f
Hours from cost = cost × hoursPer10000 / 10,000

Average hours = (hoursFromSurface + hoursFromCost) / 2
Honoraire = averageHours × costPerHour

The coefficients (c, d, e, f) vary by project type and building type, derived from Belgian architectural industry data.

API

calculateHonoraires(surface, constructionCost, options?)

Calculate architect fees for a construction project.

Parameters

| Parameter | Type | Description | |-----------|------|-------------| | surface | number | Total building surface in m² | | constructionCost | number | Net construction cost in € (excluding VAT and fees) | | options | CalculationOptions | Optional configuration |

Options

| Option | Type | Default | Description | |--------|------|---------|-------------| | costPerHour | number | 60 | Hourly rate in € | | projectType | ProjectType | 'MW' | Type of building project | | buildingType | BuildingType | 'VB' | New construction or renovation |

Returns

interface HonoraireMoyenResult {
  hoursPerM2: number;        // Hours per m² coefficient
  hoursFromSurface: number;  // Total hours from surface calculation
  hoursPer10000Euro: number; // Hours per €10,000 coefficient
  hoursFromCost: number;     // Total hours from cost calculation
  averageHours: number;      // Average of both approaches
  honoraireMoyen: number;    // Final fee in euros
}

Project Types

| Code | Dutch | French | English | |------|-------|--------|---------| | EW | Eénsgezinswoning | Maison unifamiliale | Single-family home | | MW | Meergezinswoning | Immeuble à appartements | Multi-family building | | SH | Sociale Huisvesting | Logement social | Social housing | | IL | Industrieel/Logistiek | Industriel/Logistique | Industrial/Logistics | | PG | Publiek Gebouw | Bâtiment public | Public building | | BU | Buitengewoon | Exceptionnel | Exceptional/Special | | ON | Onderzoek/Overig | Recherche/Autre | Research/Other |

Building Types

| Code | Dutch | French | English | |------|-------|--------|---------| | NB | Nieuwbouw | Construction neuve | New construction | | VB | Verbouwing | Rénovation | Renovation |

Examples

Multi-family renovation (default)

import { calculateHonoraires } from 'architect-fees-be';

const result = calculateHonoraires(2300, 3_000_000);
// Result: ~214,860€ for 3581 hours at 60€/hour

New single-family home

const result = calculateHonoraires(200, 400_000, {
  projectType: 'EW',
  buildingType: 'NB',
  costPerHour: 75
});

Industrial building renovation

const result = calculateHonoraires(5000, 2_000_000, {
  projectType: 'IL',
  buildingType: 'VB'
});

Access labels for UI

import { PROJECT_TYPE_LABELS, BUILDING_TYPE_LABELS } from 'architect-fees-be';

// Display in Dutch
console.log(PROJECT_TYPE_LABELS.MW.nl); // "Meergezinswoning"

// Display in French
console.log(BUILDING_TYPE_LABELS.VB.fr); // "Rénovation"

Validation

The function throws errors for invalid inputs:

calculateHonoraires(0, 1000000);    // Error: Surface must be greater than 0
calculateHonoraires(100, -5000);    // Error: Construction cost must be greater than 0
calculateHonoraires(100, 100000, { costPerHour: 0 }); // Error: Cost per hour must be greater than 0

TypeScript Support

Full TypeScript support with exported types:

import type {
  ProjectType,
  BuildingType,
  HonoraireMoyenResult,
  CalculationOptions
} from 'architect-fees-be';

Embeddable Widget

A ready-to-use HTML widget is included for embedding in any website.

Option 1: Embed via iframe (Recommended)

Use the hosted widget on GitHub Pages:

<iframe
  src="https://vanmarkic.github.io/ferme-du-temple/architect-fees/"
  width="100%"
  height="680"
  frameborder="0"
  style="max-width: 500px; border-radius: 8px; box-shadow: 0 2px 8px rgba(0,0,0,0.1);"
  title="Belgian Architect Fee Calculator"
></iframe>

Option 2: Self-host the widget

Copy the widget/index.html file to your project and serve it directly:

<!-- Direct include -->
<iframe src="/path/to/widget/index.html" width="100%" height="550" frameborder="0"></iframe>

Option 3: Run locally

# From the package directory
pnpm widget:serve

# Then open http://localhost:3333

Customization

The widget is a single HTML file with inline CSS/JS. You can easily customize:

• Colors: Edit the CSS variables in :root
• Language: Modify labels in the HTML
• Default values: Change the value attributes on inputs
• Styling: Adjust the CSS to match your brand

License

MIT

Contributing

Contributions are welcome! Please open an issue or submit a pull request.

Acknowledgements

This package implements the formula from the BRADA study (Belgian Research on Architects' Design Activities), a comprehensive research project analyzing architectural workload and fee structures.

Original Research

• Study: BRADA - Het Rapport (2016)
• Report: BRADA_HET_RAPPORT_20160126_JR.pdf
• Online Calculator: ArchiMath - Systeme-D

The coefficients used in this package are derived from regression analysis of real-world architectural project data collected and analyzed by the BRADA research team.

Credits

• Formula and coefficients: BRADA study / ArchiMath by Systeme-D
• TypeScript implementation: La Ferme du Temple