10 Technical Specification Items to Check When Choosing a Steel House Manufacturer

Items 1-2: profile thickness and galvanization

The thickness of structural profiles forming the backbone of a light steel building must be specified in the contract. The standard residential range is 1.2-2.0 mm; multi-storey or wide-span projects use higher values. Vague phrases like "light steel" must be replaced with explicit thickness (e.g. 1.5 mm).

Galvanization must be Z275 (275 g/m²) or above per TS EN 10346. Lower coatings such as Z140 may corrode within 5-10 years on coastal projects. The contract must include the galvanization class and the standard reference together.

• Profile thickness must be specified between 1.2-2.0 mm.
• Galvanization Z275 or higher, certified per TS EN 10346.
• Z350 is recommended for coastal projects.
• Steel grade (e.g. S350GD) must be in the contract.
• Profile manufacturer name and origin must be clear.

Items 3-4: connection type and facade panel

In light steel structures, bolts, screws and welding are used in different locations. The contract must specify connection type (bolt class 8.8, weld length, screw diameter), connection density and TS EN 1090 class. Vague terms like "standard connection" should not be accepted.

Facade panel choice directly affects thermal, acoustic and visual performance. Sandwich panels (PU, EPS, mineral wool), ABS facades, OSB + insulation + cladding offer different costs and performance. Which panel, its thickness and brand must be in the contract.

• Bolt class should be 8.8 or higher.
• Weld length and class (TS EN 1090 EXC2) must be specified.
• Facade panel type and thickness must be explicit.
• Panel thermal conductivity (λ) must be documented.
• Fire class (B-s2 d0 etc.) must be in the contract.

Items 5-6: insulation thickness and roof package

TS 825 thermal insulation regulation defines minimum insulation values per climate zone for residential buildings. Turkey is divided into 4 zones; for example, in zone 3 the exterior wall U value is around 0.4 W/m²K. Insulation thickness and material in the contract must meet this target.

A roof package is more than waterproofing. Roofing material (tile, sandwich roof panel, metal roof), slope, gutters, downpipe diameter, drainage points and roof insulation thickness (usually 80-150 mm) are separate items. Brand and thickness must be written, not "standard roof".

• Insulation must be calculated per TS 825 climate zone.
• Exterior wall insulation thickness is typically 80-120 mm.
• Roof insulation is usually 80-150 mm mineral wool or EPS.
• Gutter diameter (Ø100-Ø150) must be specified.
• Roof slope and roofing brand must be in the contract.

Items 7-8: electrical scope and warranty period

Electrical installation is often the vaguest item in turnkey contracts. Panel brand and amperage, number of breakers, sockets/switches, lighting fixture type and brand, grounding and lightning protection scope must be listed separately. If a smart-home backbone is requested, CAT6/HDMI lines should also be on the list.

Warranty must be stated separately for structural system, facade, roof, insulation and mechanical systems. Industry standard is 10 years for the structure, 5 years for facade and roof, and 2 years for mechanical. Phrases like "warranted against manufacturing defects" are too vague.

• Panel brand, amperage and breaker count must be listed.
• Number of sockets, switches and lighting fixtures must be specified.
• Grounding and lightning protection scope must be in the contract.
• Warranty must be defined per system.
• Out-of-warranty cases (wear, misuse) must be explained.

Items 9-10: assembly scope and delivery time

Assembly scope breaks into transport, crane services, installer accommodation, site safety and site cleanup. The contract must state whether each item is included in the price or billed separately. Otherwise, additional amounts surface during delivery.

Delivery time must be written explicitly in days. Instead of "around 60 days", a split timeline like "production 35 working days, shipment 5 working days, assembly 25 working days" creates a safer contract. A daily penalty clause for delays should also be included.

• Specify whether transport and crane services are included.
• Clarify installer accommodation and meals.
• Site cleanup before delivery must be in the contract.
• Production, shipment and assembly times must be split.
• Daily delay penalty must be included in the contract.

Specification summary: 10 items before contract

When all 10 items are in the contract, the boundary of work is clear for both manufacturer and client. Most disputes stem from one or more items being left verbal.

AYD Prefabrik's standard contract addresses these 10 items as separate sections and gives the client 48 hours to read before signing. Contract transparency is a quality indicator just as important as seismic performance.

• Profile and galvanization values must be backed by certificates.
• Facade and roof package must be written with brand and thickness.
• Electrical and mechanical scope must be listed item by item.
• Warranty periods must be defined per system.
• Delivery schedule and penalty clause must be in the contract.

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