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Pre-stressed concrete roof girders

prestressed concrete roof girders

A roof girder is a prefabricated structural element made of prestressed concrete used as the main load-bearing structure for the roofs of industrial, warehouse and agricultural halls. They are manufactured from C40/50 or C50/60 class concrete using prestressed concrete technology, providing spans of up to 30 meters with optimal load-bearing capacity. They are used in large-scale construction as a cost-effective solution for rapid construction of buildings without intermediate supports.

For each roof girder project, the price is calculated individually based on the span, load capacity, section type and number of elements. We guarantee comprehensive technical advice, static calculations and professional transportation and installation of prefabricated elements. We invite you to get a free quote tailored to the parameters of your building.

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Prefabricated roof girder – reliable hall construction

The roof girder is a key structural element in large-scale construction, allowing large spans to be covered without the need for intermediate supports. Prefabricated concrete elements produced by prestressing technology guarantee exceptional load-bearing capacity with relatively low dead weight. The prefabrication system ensures the highest quality workmanship and geometric precision necessary for hall structures.

The production of roof girders is based on the use of concrete of minimum class C40/50, standard C50/60 with a compressive strength of 60 MPa. The technology of prestressing with strings or cables of Y1860S7 steel with a strength of 1860 MPa allows to reduce the cross-section by 30-40% compared to reinforced concrete structures. The prestressing force introduced before concreting provides initial compression of the tensile zone.

Types of prefabricated roof girders

Prefabricated roof girders are produced in a variety of section types to suit specific construction requirements. The most popular are type I girders with a height of 80-180 cm for spans of 12-24 m. T-type girders are characterized by an upper shelf with a width of 120-250 cm, on which the roof panels are directly supported.

The gabled reinforced concrete roof girder system is the optimal solution for halls with rainwater drainage. The slope of the top flange of 3-5% eliminates the need for additional slope layers. The height at the ridge of 120-200 cm, with an eave of 80-140 cm, provides adequate rigidity while maintaining economical use of material.

Prestressed concrete technology in girder production

Prestressed concrete roof girders are manufactured with 100-150 m long prestressing strings. Prestressing strings with a diameter of 12.5-15.2 mm distributed in the lower zone of the section with a tension force of 130-195 kN/string. After the concrete reaches 70% of its strength, the tension is released and the prestressing force is transferred to the element through adhesion.

An alternative is prefabricated cable-concrete girders, where prestressing is carried out after the concrete has hardened. 7-strand cables run in channels, tensioned with hydraulic presses to a force of 2000-4000 kN. The system allows prestressing of elements with variable geometry and larger spans up to 30-40 m.

Structural parameters of reinforced concrete girders

Precast reinforced concrete girders are designed for standard loads: snow 0.7-2.0 kN/m² depending on the zone, wind 0.3-1.0 kN/m², technological installations 0.5-2.0 kN/m². Additional concentrated loads from ventilation equipment or skylights up to 50 kN. Safety factors in accordance with Eurocode 2.

The standard spacing of roof girders is 6.0 m or 12.0 m, adapted to the module of the halls. At a spacing of 6 m, TT-type or pan roof slabs are used, at 12 m – prestressed concrete slabs with higher load-bearing capacity. The system allows optimization of the number of columns and foundations.

Strut concrete roof girders Application sketch of the hall

Advantages of prefabricated roof girder

Large spans without supports – roof girder

The prestressed roof girder allows spans of up to 30 m to be covered without intermediate columns. Free internal space of halls increases functionality by 40%. The system eliminates restrictions on the arrangement of storage or production space.

Speed of roof girder installation

Roof girders assembled at the rate of 4-8 pieces per day by 100-150 tons crane. Complete 5000 m² hall roof structure realized in 7-10 days. Prefabrication reduces construction time by 60% compared to monolithic structures.

Economics of prefabricated roof girders

Prefabricated roof girders reduce construction costs by 25-35% due to lower steel consumption. Optimizing the section by prestressing saves 30% of concrete. Elimination of scaffolding and formwork reduces labor costs by 40%.

Load capacity of reinforced concrete roof girders

Reinforced concrete roof girders carry imposed loads of 3-5 kN/m² at a deflection of L/250. A load-bearing reserve of 30% allows the installation of additional installations. The system adapts to increased snow loads in mountainous areas.

Durability of prestressed concrete roof girders

Prestressed concrete roof girders have a service life of more than 100 years. C50/60 concrete with less than 4% water absorption provides F200 frost resistance. Compression eliminates scratching increasing corrosion resistance.

Prefabrication precision of prefabricated girders

Prefabricated girders maintain dimensional tolerances of ±10 mm over a length of 20 m. Perfectly flat top surface facilitates roofing installation. Factory quality control eliminates manufacturing defects.

Fire resistance of prefabricated reinforced concrete girders

Precast reinforced concrete girders provide a fire resistance class of R60-R120. The 40-50 mm concrete lagging protects the reinforcement from high temperatures. The system meets the fire protection requirements for production halls.

Versatility of roof girder application

The roof girder system adapts to different types of buildings – steel, reinforced concrete, mixed halls. Possibility of combining with existing structures for expansions. Compatibility with all roofing systems.

The use of roof girder in construction

The roof girder is widely used in all types of large-scale buildings that require large-span roofing. Prefabricated prestressed structures dominate in industrial, logistics and agricultural construction. The modular system allows the realization of halls from 500 to 50000 m² with any functional layout.

Production and industrial halls

In production halls, roof girders with spans of 18-24 m create column-free space for process lines. The system allows to run suspended cranes with a lifting capacity of up to 10 tons. The increased height of the girders 150-180 cm allows hiding ventilation installations in the girder space.

Prefabricated roof girders in heavy industry plants designed for process loads up to 5 kN/m². Reinforced support zones for overhead cranes with a lifting capacity of 20-50 tons. Vibration isolation system reduces the transmission of vibrations from machinery to the roof structure.

Warehouses and logistics centers

Distribution centers use reinforced concrete roof girders with spans of 24-30 m to maximize storage space. The absence of interior columns increases storage capacity by 25%. The high-bay racking system can be anchored directly to the girders.

In cold and freezer rooms, prestressed concrete roof girders made of C50/60 concrete resistant to freeze-thaw cycles. Tight concrete structure with absorbability <4% eliminates degradation in high humidity conditions. Ability to install heavy thermal insulation 30-50 kg/m².

Large-format retail facilities

Supermarkets and hypermarkets use prefabricated gabled beams for natural drainage. Spans of 18-24 m create an open retail space. A system of strip skylights in the ridge provides natural light.

Shopping malls use precast reinforced concrete girders as the load-bearing structure for parking floors. The load-bearing capacity of 10-15 kN/m² allows parking of cars. Slopes built into the geometry of the girder eliminate water stagnation.

Agricultural buildings

In barns and piggeries, a roof girder with a span of 12-18 m eliminates columns that hinder mechanization. Resistance to the aggressive environment of ammonia and organic acids. Gravity ventilation system integrated into the roof structure.

Grain barns and warehouses use T-type roof girders for direct support of roof panels. Spacing of 6 m is optimal for supplemental timber truss construction. Possibility of ridge skylights for natural ventilation.

Sports and performance halls

Sports venues use prefabricated roof girders with an increased height of 180-220 cm for hiding installations. Sound and lighting systems suspended from the lower flange. Acoustic soundproofing panels mounted between the girders.

Covered grandstands use cantilevered reinforced concrete roof girders with a height gradient of 8-15 m. Height gradient for visibility from the last rows. Drainage system with membrane covering.

Infrastructure facilities

Bus and streetcar depots use prestressed concrete roof girders resistant to de-icing salts. A span of 15-20 m allows vehicles to pass freely. Integrated overhead catenary for trolleybuses.

Wastewater treatment plants use prefabricated beams over process pools. Resistance to chloride corrosion of class XD3. Removable cover system for service access.

Power plants and combined heat and power plants

In the turbine halls, prefabricated reinforced concrete g irders with capacities suitable for cranes of 100-200 tons. Increased rigidity to eliminate vibrations. System of service platforms on different levels.

Aircraft hangars

Hangars for small aircraft use a roof girder with a span of 30-40 m. Clear height of 8-12 m for propeller aircraft. Sliding gate system without overhead guides.

Installation of the roof girder – execution instructions

Proper installation of prefabricated roof girders requires the use of cranes with adequate capacity and overhang, as well as an experienced installation team. The process carried out in accordance with the installation project taking into account the sequence of laying, attachment points and temporary protection. The prefabricated system allows installation regardless of weather conditions.

Site preparation

Before installation of roof girders, the execution of columns is checked – position tolerance ±20 mm, head level ±10 mm. Access roads paved with concrete slabs for cranes of 100-200 tons. Storage yard leveled, with a load capacity of min. 20 kN/m², with space for spreading the girders.

For prefabricated roof girders weighing more than 40 tons, 150-300 ton crawler cranes are used. Crane working radius of 15-25 m at full load. Verification of bearing capacity of the substrate – required static plate tests confirming the strain modulus E₂ > 80 MPa.

Preparation of girders for installation

Inspection of reinforced concrete roof girders before installation: checking dimensions, straightness, absence of transport damage. Installation of slings at the attachment points – transport hooks or wire rope loops. For girders > 18 m used traverse to equalize forces in slings.

Prestressed concrete roof girders lifted with near-target position. Angle between slings 60-90° for even distribution of forces. Securing guide ropes to control rotation during lifting.

Lifting and seating of girders

Lifting prefabricated beams at a speed of max 5 m/min to a height of 0.5 m above the assembly level. Guidance to column heads by 2-3 assemblers from directional ropes. Precision seating at a speed of 0.5-1.0 m/min in the final phase.

Positioning of prefabricated reinforced concrete girders on 200×300×20 mm elastomeric pads. Centering with respect to the column axis with a tolerance of ±10 mm. Support length minimum 250 mm, optimally 300-400 mm for long-span girders.

Stabilization and security

Temporary bracing of the first roof girder with steel lashings to adjacent foundations or columns. Minimum 2 points of stabilization at 0.3-0.4 span spacing. Rope tension of 5-10 kN to eliminate deflection from vertical.

After setting up a pair of roof girders, installation of cross bracing – steel or reinforced concrete transoms. M20-M24 bolted connections with tightening torque according to the design. Wind brace system in the roof plane every 30-60 m.

Installation of the complementary structure

On T-type prefabricated roof girders laid roof slabs directly on the top shelf. TT slabs with a span of 6-12 m, pan slabs 6-9 m, trough slabs 12-18 m. Installation rate 500-800 m²/day with one crane.

For type I reinforced concrete roof girders, steel or concrete purlins installed. Purlin spacing of 2-3 m adapted to trapezoidal sheet metal roofing. M16-M20 chemical anchors in the upper flange of the girder.

Making connections and expansion joints

Interlocking the roof slabs with prestressed concrete roof girders with C25/30 concrete in the grooves. Transverse reinforcement φ12 every 30 cm ensures spatial cooperation. Thickness of the composite layer 5-8 cm.

Expansion joints between hall segments on prefabricated girders every 60-72 m. Double columns with a gap of 2-5 cm. Flexible joint sealing with EPDM profile. Drainage system from expansion joints to gutters.

Quality control of the assembly

Survey measurements of precast reinforced concrete girders: level of the top flange ±15 mm, longitudinal axis ±20 mm, verticality of the web ±H/500. Checking the tightening torques of bolts with a torque wrench. Protocol of acceptance of each stage of assembly.

Load test of the roof girder – test load of 1.1× operational load for 24 hours. Measurement of deflections in the middle of the span and 1/4 of the length. Permissible elastic deflection L/250, permanent deflection L/500. Visual inspection of scratches.

Corrosion protection

Steel elements in roof girders – bolts, anchors, plates – protected by hot-dip galvanizing 85 μm. Welds cleaned and painted with epoxy paints. Elastomers and gaskets resistant to UV and aging.

Concrete surfaces of prefabricated roof girders in chemically aggressive halls protected with epoxy or polyurethane coatings. Hydrophobic impregnation in areas exposed to moisture. Condensation drainage system from the roof structure.

Roof girders Prefabricated prestressed concrete roof girders

Roof girder price – comprehensive calculation of hall structures

Roof girder price is shaped by the span of the structure, the type of section, the class of concrete and the degree of prestressing of the element. Valuation includes the cost of design, production of prefabricated product, specialized transport and installation by crane. Roof girders price significantly depends on the size of the order – with large halls possible quantity discounts of up to 15-20%.

Cost structure of roof girders

The main component affecting the price of roof girders is the cost of production, which accounts for 65-75% of the value. The unit price for a running meter of a girder with a span of 18 m is 2500-3500 PLN. Prefabricated roof girders price increases non-linearly with the span – a 24 m element costs 4000-7500 PLN/mb net.

Specialized transportation accounts for 10-15% of the total cost. The price of transporting reinforced concrete roof girders with low-loader trailers is 15-25 PLN/km for standard lengths. Pilotage and permits for oversized loads are an additional 2000-5000 PLN.

Price list 2024 for roof girders

In 2024, a stabilization of prefabricated prestressed concrete prices is observed after previous increases. Pre-stressed concrete roof girders price in 2024 for a complete element: span 12 m – 25000-35000 PLN, 18 m – 45000-65000 PLN, 24 m – 80000-120000 PLN, 30 m – 150000-200000 PLN.

Current rates in 2024 show that prefabricated g irders have an assembly price of 80-150 zloty/ton with a crane up to 150 tons. For heavier elements requiring cranes of 200-300 tons, the cost rises to 200-300 PLN/ton. In 2024, an apparent increase in fuel costs affecting transportation and assembly.

Price forecast for 2025

Predictions for 2025 indicate a possible price increase of 4-6% due to rising energy costs. Precast reinforced concrete girders price in 2025 will depend on the price of prestressing steel imported from China. The introduction of EU safeguard duties may raise costs by an additional 8-10%.

Low-carbon concrete girders reducing carbon footprint by 30% are expected to become widespread in 2025. The price of green roof girders will initially be 10-15% higher, but environmental subsidies may make up the difference. Automated production will reduce labor costs by 5-8%.

Cost comparison of different solutions

Economic analysis shows that roof girders prestressed price is 20-30% higher than steel for spans up to 18 m. Above 24 m, precast concrete girders become competitive. Precast roof girders total price over a life cycle of 50 years lower by 40% due to lack of maintenance.

Laminated wood structures cheaper by 15-20% for spans up to 15 m, but require fire protection. Steel-concrete composite girders more expensive by 30-40%, used for special architectural requirements.

Construction cost optimization

Reduction in reinforced concrete roof girder inputs price possible by optimizing spacing – 12 m instead of 6 m reduces the number of elements by 50%. Typification of cross-sections for the entire building reduces production costs by 10-15%. Combined orders for several investors give discounts of 8-12%.

Savings with prestressed concrete roof girders price by choosing the optimal span – it is often better to use more columns than maximum spans. Giving up gabled girders in favor of single-pitch girders saves 15-20%. Winter installation reduces the cost of cranes by 20%.

Operating costs of girders

Operation of prefabricated girders price of maintenance minimal – technical inspection every 5 years (500-1000 PLN), painting of steel elements every 10 years (50-100 PLN/girder). No maintenance of concrete throughout its life. Possible repair of mechanical damage PLN 200-500/m².

Modernization of prefabricated reinforced concrete girders reinforcement price when changing the purpose of the hall 500-1500 zł/mb. Additional external prestressing 2000-4000 zł/mb. Deformation monitoring system 50000-100000 zł for the entire hall.

Additional and hidden costs

In the calculation of the roof girder, the price should take into account: workshop and assembly design 5-10 zloty/m² of the hall, geotechnical research for the crane 5000-10000 zloty, temporary roads 100-200 zloty/mb, securing the yard 20-50 zloty/m²/month.

Additional elements affecting the roof girders price: bracing and braces 80-150 PLN/m² of the hall, purlins 100-200 PLN/m², roofing 80-250 PLN/m², skylights 500-1000 PLN/m², drainage 50-100 PLN/m².

The final prefabricated girders price of each project requires individual analysis of loads, ground conditions and utility requirements. We encourage you to contact us in order to prepare a detailed offer of the roof structure tailored to the parameters of your hall.

Here are just some of our roof girder realizations. This list includes only large investments on which our prefabricated products have appeared.

Precast concrete units are prefabricated building components produced off-site that can be assembled into larger structures at the project site. These are standard, repetitive modules produced in series at industrial plants, which greatly speed up and facilitate construction work in various construction sectors.

Reinforced concrete. prestressed concrete, post-tensioned concrete – 20+ types

Rapid modular construction of various structures

Repeatability, precision, speed of installation, durability

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    Technical parameters of the roof girder

    The roof girder is designed and manufactured in accordance with PN-EN 13225:2013 for precast concrete structural elements. Static calculations according to PN-EN 1992-1-1 (Eurocode 2) for prestressed structures. All elements have a CE declaration of performance and a B construction mark.

    Material parameters of concrete and steel

    Prefabricated roof girders are made of concrete of minimum class C40/50, standard C50/60. The characteristic compressive strength fck = 50 MPa (cylindrical), fck,cube = 60 MPa (cube ). Modulus of elasticity Ecm = 37 GPa. Exposure class XC3/XF1 for internal components.

    Prefabricated roof girders reinforced with Y1860S7 prestressing steel with a characteristic strength of fpk = 1860 MPa. Modulus of elasticity of steel Ep = 195 GPa. Initial prestressing force 0.75×fpk = 1395 MPa. Ad hoc compression loss 8-12%, delayed compression loss 18-22%.

    Types and dimensions of girders

    Standard cross-sections of reinforced concrete roof girders: type I – height 80-180 cm, bottom flange width 40-60 cm, top flange width 60-120 cm, web thickness 12-20 cm; type T – height 100-200 cm, flange width 120-250 cm, flange thickness 25-35 cm; type L for edge girders.

    Typical spans of prestressed concrete roof girders: 12.0 m (weight 8-12 tons), 15.0 m (12-18 tons), 18.0 m (18-25 tons), 21.0 m (25-35 tons), 24.0 m (35-45 tons), 27.0 m (45-60 tons), 30.0 m (60-80 tons). Modular lengths in 3.0 m increments.

    Strength parameters

    Design bending capacity of prefabricated girders: MRd = 800-5000 kNm, depending on the section. Shear resistance VRd = 400-2000 kN. Maximum imposed load 3-8 kN/m² at 6 m spacing, 2-5 kN/m² at 12 m spacing.

    Precast reinforced concrete girders – allowable deflection: L/250 from total loads, L/350 from variable loads. Natural frequency > 3 Hz for halls without cranes, > 5 Hz with cranes. Dynamic coefficient 1.2-1.4.

    Reinforcement and compression

    Prestressing reinforcement in the roof girder: 7-splice strings Y1860S7 diameter 12.5 mm (140 mm²) or 15.2 mm (150 mm²). Number of strings 12-40 pieces depending on the span. Distribution in the stretched zone with an eccentricity of 40-80 cm.

    Ordinary reinforcement of roof girders: steel A-IIIN (B500B), stirrups φ8-12 every 10-20 cm in buttress zones, every 25-30 cm in the middle of the span. Structural reinforcement of the upper flange mesh φ8 every 15 cm. Reinforcement for lateral forces from prestressing.

    Support zones and connections

    Supporting prefabricated roof girders on columns: length of support min. 25 cm, elastomeric washer 20 mm. M24-M30 steel anchors to prevent displacement. Pivot bearings for spans > 24 m.

    Connections between girders of reinforced concrete roof girders: transverse bracing every 6-12 m, steel ties φ20-32 mm. Steel or reinforced concrete purlins for stiffening the upper flange. Expansion joints every 60-72 m in the longitudinal direction of the hall.

    Fire resistance and durability

    Fire resistance class of prestressed concrete roof girders: R60 for 35 mm lagging, R90 for 45 mm, R120 for 55 mm. Increased lagging in the buttress zone. Possibility of protection with intumescent coatings for R180.

    Durability of precast beams: design life of 100 years in exposure class XC3. Concrete water absorption < 4%, frost resistance F200. Chloride diffusion coefficient < 8×10-¹² m²/s. Carbonation < 3 mm after 50 years.

    Dimensional tolerances

    Accuracy of precast reinforced concrete girders: length ±20 mm, height ±10 mm, straightness 10 mm/10 m. Position of prestressing strings ±5 mm. Smoothness of the surface – unevenness max 5 mm/2 m.

    Transportation and storage

    Transport of the roof girder: low-loader trailers with a capacity of 40-100 tons. Support points at a distance of 0.2L from the ends. Maximum transport length 30 m (exceptionally 36 m). Storage on wooden sleepers at support points.

    Fixed height I beam prestressed concrete roof girders without supports

    Fig. 1. I-joists of prestressed concrete of constant height without reinforcement of the ends of the elements

    Fixed height I beam prestressed concrete roof girders with supports

    Fig. 2. I-beam prestressed concrete girder of constant height with reinforcement of the ends of the elements – with support blocks

    Fixed height I beam prestressed concrete roof girders with supports and additional openings

    Fig. 3. I-beam reinforced prestressed concrete girders of constant height with reinforcement of the ends of the elements (support blocks) and openings for the passage of installations

    Fixed height I beam prestressed concrete roof girders with end supports and an additional bracket

    Fig. 4. Fixed-height prestressed I-beam with support blocks and an additional bracket

    Variable height I beam gabled prestressed concrete girders with supports

    Fig. 5. I-joists of prestressed concrete of variable height with reinforcement of the ends of the elements – with support blocks

    Variable height I beam gabled prestressed concrete roof girders with end supports and additional openings

    Fig. 6. I-beam prestressed concrete beams of variable height with support blocks and holes for installations

    Variable height I beam gabled prestressed concrete roof girders with end supports additional supports and openings

    Fig. 7. I-beam prestressed concrete girders of variable height with support blocks, holes for installation and additional supports

    Variable height prestressed concrete girders with rectangular cross section

    Fig. 8. Variable-height, gabled prestressed concrete girders

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