Timber Structures

Why does the design of timber structures require specialized engineering expert review?

Wood is the only building material whose mechanical characteristics are fundamentally anisotropic: the strength along and across the fibers varies significantly, and humidity and temperature deformations are unpredictable without taking into account specific operating conditions. Designing wooden structures without a deep understanding of the behavior of the material under long-term and short-term loads, without taking into account the class of operating conditions and without correctly assigning fire protection measures inevitably leads to either excessive consumption of material or expert comments - and often to both results at the same time. AYU-Project is developing section KD consisting of design documentation and working documentation: from calculation justification to a full set of working drawings, in which the strength, durability and fire safety of wooden structures are ensured in a regulatory and engineering correct manner.

What is included in section KD of project documentation?

Section KD covers all wooden load-bearing and enclosing structural elements of the building and is developed in accordance with the requirements of Government Decree of the Russian Federation No. 87 dated 16.02.2008 No. 87 (as amended on 21.10.2025) “On the composition of sections of design documentation and requirements for their content.” At the DD stage this is: an explanatory note describing the design decisions taken, calculation justifications for load-bearing elements, layout diagrams with element brands, material specifications and requirements for fire protection and biosecurity. The following are being produced at the WD stage:

• Element layout diagrams - plans and sections with the arrangement of beams, racks, trusses, purlins and panels with axial references and marks;
• Drawings of structural elements - geometry of sections, lengths, notches, grooves and holes for fasteners;
• Connection nodes - detailed solutions for joints and junctions: dowel, bolted, keyed connections, metal toothed plates, steel liners and dowel plates;
• Schemes of rafter systems - for pitched roofs: indicating the sections of rafters, struts, racks, ridge girder, wind connections and support points on the mauerlat;
• Specifications of wood and hardware - indicating the species, strength class, moisture content and grade of wood, steel classes of fasteners;
• Technical requirements - on fire retardant and bioprotective treatment, indicating the groups of fire retardant effectiveness of the compositions used.

What kind of wooden structures do we design?

AYU-Project carries out the design of wooden structures for civil, public and industrial construction projects - using both traditional and modern wood-based engineering materials:

• Beams and purlins - from solid, laminated and LVL wood; calculations for bending, shear force and deflection taking into account long-term loads and creep of the material;
• Trusses - triangular, trapezoidal, arched; from laminated veneer lumber or solid lumber; calculation of forces in belts and lattice, taking into account the compliance of joints;
• Floors - beams made of solid and laminated wood, panels made of CLT (cross-laminated timber); selection of the type of system based on loads, spans and sound insulation requirements;
• Rafter systems - layered and hanging rafters, combined systems with board-nail and glued elements; checking the components for the perception of thrust and snow loads;
• Load-bearing walls and partitions made of CLT - panel structural systems for low- and mid-rise buildings; calculation for vertical and horizontal loads;
• Frame systems - post-beam structures for public and industrial buildings; spatial rigidity is provided by a system of connections or rigidity diaphragms;
• Long-span glued structures - arches, frames and beams of variable section for sports halls, covered markets, covered parking lots and agricultural buildings;
• Wooden structures as part of combined systems - wooden floors and roofs in combination with reinforced concrete or metal supporting frame.

Why are glued-laminated timber structures better than solid timber in commercial construction?

Laminated timber is a fundamentally different structural material than just “improved wood”. Due to the cross arrangement of layers and the rejection of defective areas during gluing, laminated veneer lumber and LVL beams demonstrate stable design characteristics that significantly exceed those of solid lumber of the same section. This allows spans of up to 30 meters or more to be covered without intermediate supports - which in commercial construction means freedom of planning decisions and a reduction in the number of foundation supports. CLT panels in multi-storey construction are competitive in installation speed with monolithic reinforced concrete: factory precision manufacturing eliminates “wet” processes and significantly reduces the construction time of the load-bearing contour. AYU-Project selects the type of wooden structural system not by default, but based on the results of a feasibility study of alternative options for a specific facility.

How is fire safety addressed when designing wooden structures?

Fire safety is not an optional add-on to a structural section, but an integral part of it, determining the choice of sections, treatments and design solutions. Without special fire retardant treatment, wooden structures have a fire hazard class no higher than K3 and can be used in load-bearing elements only in buildings with a structural fire hazard class no higher than C2. AYU-Project provides an integrated approach to fire safety requirements when developing the design documentation section:

• Calculation of actual fire resistance limit - for load-bearing wooden elements, the normalized charring depth is calculated in accordance with SP 64.13330.2017; sections are selected taking into account the residual section after charring in a standardized time;
• Purpose of fire retardant treatment - selection of fire-retardant impregnations and coatings with a fire-retardant efficiency group that provides a standardized fire resistance limit; reflected in the technical requirements of section KD;
• Structural fire protection measures - the use of fire-resistant cladding, fillings and fire-resistant joints where active fire protection is impossible or economically infeasible;
• Consistency with section fire safety (fire safety) - design solutions for the design documentation section are developed in coordination with fire safety requirements for the building as a whole.

What standards are used to design wooden structures?

The regulatory framework for the design of wooden structures includes both general building codes and documents specific to individual types of materials and structural systems. AYU-Project carries out design strictly according to current editions:

• SP 64.13330.2017 “Wooden structures” (updated edition of SNiP II-25-80) - the main document regulating the calculation and design of load-bearing elements made of solid and laminated wood; taking into account classes of operating conditions, load duration and creep coefficients;
• SP 515.1325800.2022 “Buildings made of laminated timber” - requirements for load-bearing capacity, deformability and fire safety of structural systems made of laminated timber;
• GOST 20850-2014 “Glued laminated load-bearing structures” - technical requirements for prefabricated glued-laminated load-bearing structures;
• GOST 33124-2014 “LVL timber” - technical specifications for LVL timber (laminated veneer lumber); taken into account when selecting and calculating LVL beams and racks;
• SP 20.13330.2022 “Loads and impacts” - standard values ​​of constant, snow, wind and operational loads;
• Government Decree of the Russian Federation No. 87 dated 16.02.2008 No. 87 (as amended on 21.10.2025) “On the composition of sections of design documentation and requirements for their content” - regarding the structure and content of DD for the design section.

How is the design process for the KD section in AYU-Project structured?

The development of the KD section in AYU-Project is organized as a structured process in which each stage undergoes internal verification before the result is transferred to the customer.

Stage 1 - Analysis of initial data. We study technical specifications, architectural solutions, loads, climatic conditions of the site, requirements for the functional and structural fire hazard class of the building.

Stage 2 - Selection of structural system. We determine the type of wooden structural system - beam, frame, CLT panel or combined - with justification for the choice and, if necessary, comparison of alternatives.

Stage 3 - Calculation justification. We carry out calculations of load-bearing elements according to the first (strength, stability) and second (deflections, deformations) groups of limit states, taking into account classes of operating conditions and load duration coefficients. We calculate the connection nodes.

Stage 4 - Development of DD. We produce a set DD for examination: explanatory note, calculation justifications, diagrams, specifications.

Stage 5 - Development of WD. We produce a complete working set KD: drawings of elements, joints, rafter diagrams, specifications and technical requirements for fire protection and biosecurity.

Stage 6 - Expert-review support. We eliminate expert comments free of charge within the framework of the contract; if necessary, we coordinate adjustments with the fire safety section and architectural solutions.

Why do construction companies choose AYU-Project as a subcontractor under section KD?

The construction business working with wooden structures is faced with a narrow specialization: there are significantly fewer competent designers on the market who can calculate a glued frame or CLT floor as confidently as a reinforced concrete frame than monolithic specialists. AYU-Project addresses this need in a comprehensive manner:

• Accurate calculation taking into account the specifics of the material - calculations of wooden structures are carried out with mandatory consideration of the class of operating conditions, humidity, creep and load duration - factors that are absent in the calculation of steel and reinforced concrete structures;
• Optimization of sections and materials - selection of an economically justified type of wooden system and minimally sufficient sections of elements reduces direct costs of materials without compromising on load-bearing capacity;
• Comprehensive study of fire safety - fire safety requirements are integrated into section KD, and are not delegated to adjacent sections as “someone else’s task”;
• Guarantee of passing expert review - documentation is drawn up in accordance with the requirements of Government Decree of the Russian Federation No. 87 dated 16.02.2008 No. 87 (edited by 21.10.2025), comments are corrected free of charge;
• Interdivisional coordination - Design documentation is developed in conjunction with quality assurance, design materials, architectural and fire safety solutions within a single AYU-Project team;
• Subcontracting across Russia, 8+ years of experience - SRO, specialists in the NOPRIZ register, implemented objects in various climatic zones of the country.

How much does it cost and in what time frame is the design documentation section developed?

The cost of designing wooden structures is determined by the type of structural system, the volume and complexity of calculation tasks, the materials used and the composition of the stages design documentation and working documentation. For objects of medium complexity, the estimated development time for section KD of stage DD is 2-4 weeks; stages WD - 3-7 weeks. An accurate cost and time estimate is provided based on ToR or available source data - send a request and the project manager will contact you within one business day.