How to Compare Prefab & Steel House Quotations: Uncovering Hidden Costs & Scope Gaps
Procuring a prefabricated or cold-formed steel home frequently presents clients with wide pricing discrepancies. When two bids for identical square meterage vary by 30% to 80%, the divergence invariably stems from scope omissions, sub-grade materials, and unaccounted on-site logistics expenses.
The 8-Point Forensic Quotation Checklist
- Floor Area Definition (Gross External vs Usable Net]: Does the quoted square meterage reflect external footprint including roof overhangs, or net usable internal heated floor space (TFA]?
- Structural Steel Specification & Zinc Coating: Is the frame roll-formed from S350GD high-tensile structural steel or sub-grade mild steel? Does it specify mandatory Z275 (275 g/m²] continuous galvanizing?
- Envelope Thermal Layers & Insulation Depth: Is there a continuous exterior insulation wrap to eliminate thermal bridging, or merely inadequate foam infill between studs?
- Glazing Performance: Are windows triple-glazed with warm-edge spacers (Uw ≤ 0.80 W/m²K] or baseline builder-grade double glazing (Uw ≥ 1.4]?
- Contractual Airtightness Warranty: Does the contract legally commit to a certified ISO 9972 Blower Door test (n50 ≤ 0.60 h⁻¹] prior to handover?
- HVAC & MVHR Ventilation Inclusion: Does the MEP package include an accredited mechanical ventilation system with heat recovery, or merely passive extract vents?
- Freight, Lifting & Site Logistics: Are transport freight, customs clearance, crane hire, and site supervision personnel included, or billed retroactively as extras?
- Engineering Compliance & Permit Dossiers: Are localized Eurocode structural calculation books and architectural permit packages provided?
SerVilla Transparent Delivery Packages (P1 – P4]
SerVilla quotations feature unambiguous scopes categorized into 4 contractual tiers:
- P1 Structural Frame Kit: Precision roll-formed CFS framing, anchor bolts, assembly hardware, and BIM engineering plans.
- P2 Weathertight Shell: Frame plus external continuous insulation, Passivhaus triple-glazed joinery, and smart weather membranes.
- P3 Advanced Enclosure (Most Popular]: Complete thermal shell plus interior service cavities, insulation batts, drywall linings, and pre-ducted MVHR.
- P4 Turnkey Finish: Complete interior architecture, sanitaryware, flooring, tiling, and commissioned heating systems.
Editorial Disclosure & Engineering Note:
Analysis presented in this guide reflects Eurocode structural benchmarks, Passive House Institute physics, and over two decades of SerVilla international cold-formed steel manufacturing experience. Custom statutory site verification is conducted for every individual plot.
