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Build Cost Calculator – Terms of Use & Disclaimer

Build Cost Calculator – Terms of Use & Disclaimer
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Purpose of Tool:

The Houz Design Build Cost Calculator is provided as a general guide to help users estimate potential construction costs for residential projects such as house extensions, loft conversions, and new builds.

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Cost Data Used:

The estimates generated by this tool are based on average market rates as of 2025, including publicly available data from sources such as RICS, FMB, Checkatrade, and regional cost benchmarks. The figures used are:

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Extension (per m²):

• Standard quality: £1,800/m²
• Good quality: £2,300/m²
• High quality: £2,800/m²

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Loft Conversion (per m²):

• Standard: £1,500/m²
• Good: £1,800/m²
• High: £2,200/m²

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New Build (per m²):

• Standard: £2,000/m²
• Good: £2,500/m²
• High: £3,000/m²

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Note: These rates include typical construction costs but exclude VAT, professional fees, abnormal ground conditions, planning or engineering costs, or specialist finishes.

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Important Disclaimers:

• The figures generated by this tool are approximate and for informational purposes only.
• This calculator does not constitute a formal quotation, estimate, or cost plan.
• Final construction costs will depend on numerous factors, including site conditions, location, contractor pricing, material availability, specification changes, and third-party services.
• Houz Design accepts no liability for decisions made based on this calculator or for any discrepancies between estimated and actual costs.

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User Responsibility:

By using this tool, users accept that it is only intended as a basic guide, and that formal project costs should always be confirmed via a detailed consultation and fee proposal from Houz Design or another qualified professional.

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Intellectual Property:

The content, design logic, and cost data within this tool are the property of Houz Design and may not be copied, distributed, or embedded elsewhere without permission.

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Final Note:

If you're planning a project, we recommend contacting us directly to receive a tailored fee proposal and project-specific guidance.

Full Disclaimer & Cost Basis

This Advanced Build Cost Calculator is intended for informational and guidance purposes only. The figures produced are estimates based on a combination of:

  • Industry-standard price guidance from the Royal Institution of Chartered Surveyors (RICS), Build Cost Information Service (BCIS), Homebuilding & Renovating Magazine, and comparable cost indices from professional quantity surveyors and developers.

  • Real-world pricing experience from recent Houz Design projects across Scotland, covering extensions, loft conversions, and new builds.

  • Adjusted ranges based on common features like large glazing, steelwork, vaulted ceilings, and premium finishes — which can substantially increase average build costs.

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Cost Basis Used:

  • Base build rates per m²:

    • New Build: £1,500–£2,200/m² depending on spec

    • Extension: £1,800–£2,600/m² depending on access/complexity

    • Loft Conversions: £1,600–£2,400/m²

  • Feature Add-ons:

    • Large sliding doors: ~£2,000 each

    • Rooflights/Velux: ~£800 each

    • Structural steel packages: ~£2,500–£6,000 depending on span

    • Heat pump installation: ~£7,000–£12,000 (ASHP)

    • Premium finishes: +£50–£100/m² uplift

    • SAP/U-value compliance and energy systems: £300–£1,200 depending on method and scale

These values are updated periodically to reflect market conditions but should still be treated as indicative, not final.

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Legal & Usage Notes

  • The results generated by this tool do not constitute a quotation, contract, or legally binding agreement.

  • Houz Design is not liable for any financial or planning decisions made based on this tool alone.

  • All users are advised to seek a formal architectural consultation and proposal before proceeding with any construction or planning applications.

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