SIA 118/265:2004 – General Conditions for Timber Construction
The SIA 118/265:2004 norm, also registered as SN 507 265, constitutes the general contract conditions for timber construction within the Swiss building industry. Issued by the Swiss Society of Engineers and Architects (SIA), this 2004 edition replaces the organizational part of the former norm SIA 164 (1981/92) and norm SIA 231 (1989). It belongs to the series of General Conditions for Construction (ABB) and serves as a detailed supplement to the overarching SIA 118 framework, specifically addressing the rights and obligations of builders and contractors in wood-based structures.
The scope of this document encompasses all timber buildings and structures, particularly those governed by SIA 265 (Timber Construction) and SIA 265/1 (Timber Construction – Supplementary Provisions). It is organized into a general section covering contract types, quality management, and remuneration, and a specific section (Section 8) dedicated to the technical terminology and measurement rules unique to wood construction. Key regulatory domains include tendering processes, execution controls, and precise definitions for various wood-working techniques and elements such as glulam, log construction, and roundwood.
The following sections detail the contractual requirements, quality management levels, and standardized measurement procedures essential for compliance and project delivery in the Swiss timber industry.
Contractual Framework and Tendering
The norm specifies that for a project to be legally binding under these terms, the parties must explicitly designate it as a contract component. In the event of a conflict between documents, SIA 118 takes precedence. The tendering phase requires that specific requirements exceeding technical norms must be detailed in the Besondere Bestimmungen (Special Provisions) or the bill of quantities.
- Tendering Documents: Must follow Articles 5 to 14 of SIA 118 and may utilize the Normpositionen-Katalog (NPK) 102.
- Contractor’s Offer: Includes static calculations for temporary site installations, scaffolding, and auxiliary structures as part of the total price.
- Project Variants: Contractors may submit their own variants, which the client is prohibited from sharing with competitors under the Federal Act against Unfair Competition (UWG).
Quality Management and Responsibilities
The document defines specific tasks for the client and the contractor to ensure structural safety, building physics, and fire protection compliance. Quality management is categorized into three intensity levels based on project risk and complexity.
- Level I: Standard practice without a formal QM system.
- Level II: Requires a documented QM system.
- Level III: Requires a certified QM system based on SN EN ISO 9001.
- Project Leadership: The client typically appoints a Gesamtleiter (Project Lead) to coordinate specialists and manage the information flow.
Technical Definitions and Woodwork Terminology
Section 8 provides authoritative definitions for technical terms used in Swiss timber engineering. These definitions ensure a common language between architects, engineers, and wood workers.
- Abgratungen: Beveled cuts on hip rafters parallel to the roof surface.
- Blockbau: Wall construction using horizontally layered round or square timber.
- Dollen: Dowels used for shear-resistant connections between superimposed components.
- Setzmass: The anticipated height reduction in log or chalet buildings due to wood drying after assembly.
- Schwebepfosten: Floating posts in log walls designed to allow for the settling of the structure without bearing vertical loads.
Measurement Rules for Timber (Ausmassbestimmungen)
Precise calculation rules are established for various wood types to ensure transparent remuneration. Calculations require specific decimal accuracy: 2 decimals for length, area, and mass; 3 decimals for volume.
- Roundwood (Rundholz): Measured in meters for diameters < 0.16 m; measured in cubic meters for diameters ≥ 0.16 m based on the center diameter.
- Sawn Timber (Vollholz): Measured in meters if the cross-section is < 100 cm²; measured in cubic meters if ≥ 100 cm².
- Log Construction: Measured by effective wall area in square meters; openings < 1.00 m² are not deducted.
- Glue-Laminated Timber (Brettschichtholz): Measured in cubic meters or by piece; deductions for notches only occur if they exceed 0.06 m³.
Frequently Asked Questions
Does SIA 118/265 replace the general SIA 118 norm?
No, it supplements SIA 118 specifically for timber construction. In case of discrepancies, SIA 118 remains the primary authority unless otherwise specified.
Who is responsible for the stability of temporary site scaffolding?
According to section 1.2.1, the contractor is responsible for the static calculations and safety of all construction site installations and scaffolding.
At what diameter is roundwood measured in cubic meters instead of linear meters?
Roundwood with a median diameter under 0.16 m is measured in meters, while those 0.16 m and larger are calculated in cubic meters.
Are window openings deducted from the total measurement of a log wall?
Openings in log construction are only deducted from the square-meter calculation if they are 1.00 m² or larger.
What are the required moisture content levels for timber frame components?
Annex B.2.2 stipulates that frame components with cladding on both sides must have a moisture content between 9% and 15%.
What is the 'Setzmass' in log construction?
It is the mass by which the wall height in log or chalet buildings decreases after assembly due to the natural drying of the timber.
What level of measurement precision is required for volumes?
Volume calculations (in cubic meters) require a precision of three decimal places.
Who bears the cost of weather protection for timber components during assembly?
The protection of components against weather and damage until the agreed handover to the builder is an included service of the contractor.
