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Queen Post
Interior structure of a covered bridge that uses a queen-post structure
Interior structure of a covered bridge that uses a queen-post structure
AncestorTruss bridge
RelatedNone
DescendantNone
CarriesPedestrians, livestock, vehicles
Span rangeshort to medium
Materialwood planks
MovableNo
Design effortmedium
Falsework requiredSometimes

A queen post is a tension member in a truss that can span longer openings than a king post truss. A king post uses one central supporting post, whereas the queen post truss uses two.[1] Even though it is a tension member, rather than a compression member, they are commonly still called a post. A queen post is often confused with a queen strut, one of two compression members in roof framing which do not form a truss in the engineering sense.[2]

The double punch truss appeared in Central Europe during the Renaissance.[3]

Architecture

[edit]
The queen posts are the second and third (from left) vertical posts visible in the photo, visibly thicker than the other posts.

A queen-post bridge has two uprights, placed about one-third of the way from each end of the truss. They are connected across the top by a beam and use a diagonal brace between the outer edges. The central square between the two verticals is either unbraced (on shorter spans), or has one or two diagonal braces for rigidity. A single diagonal reaches between opposite corners; two diagonal braces may either reach from the bottom of each upright post to the center of the upper beam, or form a corner-to-corner "X" inside the square.[4]

See also

[edit]

References

[edit]
[edit]
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Queen post

View on Grokipedia
from Grokipedia
A queen post truss is a type of vertical timber or steel roof truss characterized by two principal vertical posts, known as queen posts, that extend from the tie beam to the underside of the principal rafters, dividing the span into three equal parts and providing support for pitched roofs over medium-length openings typically ranging from 8 to 12 meters (26 to 40 feet).[1][2] This design, which forms a series of four interconnected triangles through the addition of diagonal struts and horizontal straining beams, enhances structural stability by countering the tendency of the tie beam to sag under load while distributing forces efficiently across the framework.[3][2] Originating from traditional timber framing techniques used for centuries in European and American architecture, the queen post truss evolved as an extension of the simpler king post truss—replacing a single central post with two to accommodate wider spans without excessive material use.[1][4] Key components include the bottom chord or tie beam (in tension), top chords or principal rafters (in compression), the two queen posts (primarily in tension to prevent beam deflection), diagonal struts (handling compression or tension), and ancillary elements like purlins for roof covering support and straining sills or beams to reinforce the structure against lateral forces.[5][3] With a typical roof pitch of 30 to 45 degrees, it offers versatility in material choice—traditionally hardwood or softwood timber, but adaptable to steel for modern applications—and is prized for its cost-effectiveness, aesthetic appeal in exposed ceiling designs, and ability to provide even load distribution in low- to medium-rise buildings.[1][2] Commonly employed in residential homes, agricultural barns, commercial structures, and even historic covered bridges, the queen post truss excels in scenarios requiring spans beyond the king post's capacity (under 8 meters) but short of more complex designs like the Howe or Pratt trusses, though it is limited by its unsuitability for spans exceeding 12 meters or heavy snow loads without reinforcement.[5][4][6] Its enduring popularity stems from straightforward fabrication, reduced labor compared to larger trusses, and compatibility with prefabricated construction methods, making it a staple in sustainable building practices where timber's renewability is leveraged.[1][7]

History

Origins

The queen post truss emerged in late 12th-century European architecture as a key innovation in timber roof construction, enabling the support of wider spans in Gothic buildings. The earliest documented example appears in the roof of St Hugh's Choir at Lincoln Cathedral in England, built between 1192 and 1200, where pairs of vertical queen struts rise from the tie beam to support the principal rafters, forming equilateral triangular frames that achieve a clear span of about 42 feet (12.8 meters). This design addressed the structural challenges of tall, open interiors by distributing loads efficiently through compression in the struts, marking a shift toward more sophisticated wooden framing techniques in medieval England.[8] In medieval Gothic architecture, the queen post played a vital role in spanning larger distances without intermediate columns or excessive roof height, which was essential for the expansive naves and halls of churches and secular buildings. By the 13th and 14th centuries, such trusses were adapted for use in English tithe barns and great halls, where the vertical posts and horizontal tie beams provided stability for spans up to 30 feet (9 meters), as seen in surviving rural structures across southern England.[9] These early applications prioritized durability in agrarian and ecclesiastical contexts, reflecting the growing demand for versatile timber systems amid the expansion of Gothic style. The development of the queen post drew from broader engineering principles inherited from Roman and Byzantine traditions, where truss-like assemblies using tension and compression members supported basilica roofs and domes, later adapted to abundant local timber resources in northern Europe. A prominent, albeit debated, instance is the Westminster Hall roof in London, reconstructed around 1396 under royal carpenter Hugh Herland, which has been interpreted as integrating elements akin to queen struts alongside hammerbeams to span 68 feet (20.7 meters) uninterrupted, showcasing the evolution toward hybrid forms in high-status architecture.[10]

Evolution in Timber Framing

The queen post truss, originating in medieval Europe as a simple tension-based roof structure, evolved significantly during the post-medieval period through refinements that enhanced its load-bearing capacity and adaptability to larger spans.[11] In the 16th and 17th centuries, English architects such as Inigo Jones and Christopher Wren introduced and advanced queen post designs, drawing from Italian influences like those documented by Andrea Palladio and Sebastiano Serlio, to support ridged and flat roofs in public buildings and churches. By the early 18th century, these trusses incorporated iron straps and tension bolts for joint reinforcement, as seen in structures like Nicholas Hawksmoor's St Alphege Church in Greenwich (1710-1714) and James Gibbs' St Martin-in-the-Fields portico (1722-1726), allowing for spans up to 18 meters while maintaining structural integrity.[11][12] In North America, colonial adaptations appeared in the mid-18th century, particularly in Southern architecture; for instance, St. Michael's Church in Charleston, South Carolina (1751), employed queen post trusses with wrought iron U-straps to secure posts to tie beams, enabling spans over 25 feet in churches and residences amid growing commercial demands. These advancements spread the design's use across Europe and beyond, reflecting broader European timber framing traditions.[13] During the 19th century, the queen post truss proliferated amid the Industrial Revolution, becoming a staple for factory and warehouse roofs requiring clear spans without internal supports. In Britain and Ireland, it supported industrial buildings like those in Belfast, where queen post variants handled spans of 9 to 18 meters in textile mills and warehouses from the 1830s onward, often combined with iron ties for enhanced durability.[14] Architects of the Gothic Revival, including Augustus Welby Northmore Pugin, indirectly bolstered its revival by championing medieval-inspired timber construction in ecclesiastical and domestic projects, emphasizing authentic historical forms over classical alternatives and influencing designs in structures like Pugin's restorations and new builds during the 1840s.[15] By the early 20th century, the queen post truss declined in new construction as steel framing and reinforced concrete offered greater spans and fire resistance for industrial and commercial applications, rendering timber variants obsolete in most modern builds. However, preservation movements from the mid-20th century onward revived interest, with efforts to restore historic examples in places of worship and colonial sites, such as Charleston's Nathaniel Russell House (1808).[16]

Design and Components

Structural Elements

The queen post truss is characterized by its primary structural elements, which include two vertical queen posts, a horizontal tie beam at the base, principal rafters forming the sloping sides, diagonal struts, and a straining beam or sill connecting the tops of the queen posts.[17][18][5] The queen posts, positioned symmetrically at the one-third points along the span, rise vertically from the tie beam to provide intermediate support, dividing the span into three equal parts to distribute forces evenly.[17] In terms of geometric arrangement, the principal rafters extend from the ends of the tie beam upward to meet at the ridge or peak, enclosing the queen posts and straining beam within a triangular framework that incorporates an interior rectangular form for enhanced stability, with diagonal struts connecting the queen posts to the rafters to form additional triangles.[19] The queen posts often support purlins at mid-height along the rafters, facilitating the attachment of roof covering materials.[17] Typical spans for queen post trusses range from 20 to 60 feet (6 to 18 meters), making them suitable for moderate roof widths in timber-framed structures. Connections between these elements primarily utilize mortise-and-tenon joints, secured with wooden pegs to ensure rigidity and load transfer in traditional timber construction.[18][17] Variations may incorporate scarf joints at the ends of the tie beam or straining sill to accommodate longer spans by splicing timbers end-to-end.[18]

Load Distribution Mechanics

In a queen post truss, vertical loads from the roof, such as dead weight, snow, or live loads, are primarily transferred through the principal rafters and diagonal struts to the straining beam and supports, with the queen posts in tension connecting the tie beam to the straining beam to prevent deflection and outward spread of the rafters at the eaves.[17] This load path ensures that the truss maintains its geometric stability under symmetric loading conditions, with the queen posts acting to resist tensile forces between the tie beam and the horizontal straining beam.[7] The queen posts experience primarily axial tension to support the straining beam and counteract the tendency of the tie beam to sag, while the tie beam endures tension to resist the horizontal thrust generated by the inclined rafters; additionally, shear forces arise at the joints where the rafters and struts connect to the other members, requiring robust joinery to resist these transverse stresses.[17] Under uniform symmetric loading, the tension in each queen post depends on the geometry and load distribution, though asymmetric loads like wind can induce bending moments in the tie beam, amplifying shear demands at these connections.[7] Analysis of internal forces in a queen post truss typically employs the method of joints, a static equilibrium technique that isolates each joint to solve for member forces using the equations ∑Fx=0\sum F_x = 0 and ∑Fy=0\sum F_y = 0.[20] For a simplified symmetric case with total vertical load WW uniformly distributed over span LL and truss height hh, full analysis using the method of joints accounts for rafter inclinations, joint reactions, and member orientations to determine forces in the queen posts and other elements. Stability in the queen post configuration relies on the central portion of the tie beam, known as the straining beam, which provides continuity to counter uplift forces from wind or seismic events by distributing tensile stresses across the full bottom chord and resisting localized deformation.[17] Common failure modes include buckling of the principal rafters under excessive compression, particularly if slenderness ratios exceed design limits or lateral bracing is inadequate, or excessive tension leading to failure in queen posts or tie beam without proper sizing, potentially causing truss collapse.[21]

Construction and Assembly

Traditional Methods

In traditional queen post truss construction, carpenters selected durable hardwoods like oak for principal members such as posts and beams due to its superior compression strength and resistance to decay, while softwoods like pine or fir were increasingly used for secondary elements like tie beams by the 17th century as oak supplies diminished.[11][12] Timbers were air-dried or seasoned for 1-2 years prior to use to minimize shrinkage, warping, and joint loosening, a practice emphasized in 18th-century treatises to ensure long-term structural integrity.[11][22] The assembly process commenced on the ground, where timbers were squared, marked, and precisely cut for mortises and tenons using hand tools including draw knives for chamfering and surface planing, adzes for rough shaping and smoothing, chisels for joint details, and framing squares for layout accuracy.[23] Once prepared, the truss components—such as the tie beam, queen posts, and principal rafters—were hoisted into position using temporary scaffolding, ropes, pikes, and manpower, often requiring teams of 6-10 workers to lift and align bents vertically in a "centre line framing" method before securing them to wall plates.[23][11] Joints were formed exclusively through interlocking mortise and tenon connections, secured by driving hardwood wooden pegs known as trunnels—typically oak dowels one-third the length of the tenon—into slightly offset holes to create a draw-bored effect that tightened the assembly over time, with no metal fasteners employed until their introduction in the 18th century for added tension in larger spans.[23][11][12] Trunnels were hammered in from both sides using heavy mauls, ensuring a firm, pegged union that relied on the natural swelling of seasoned wood under varying humidity.[23] To verify structural soundness, craftsmen performed quality checks during and after raising, using plumb bobs to confirm the vertical alignment of queen posts, spirit levels or water levels for the horizontal tie beam, and string lines or diagonal measurements to ensure the overall truss remained square and true, preventing uneven load distribution.[23][11] These manual verifications, integral to pre-industrial craftsmanship, allowed adjustments with temporary braces before final pegging, drawing on established carpentry principles to support efficient tension and compression forces in the truss.[23]

Modern Adaptations

In the 20th and 21st centuries, queen post truss designs have shifted from solid timber to engineered wood products like glued-laminated timber (glulam), which provides enhanced strength, dimensional stability, and the ability to form curved members such as bottom chords for spans up to 40 feet (12 meters).[18][2] Steel reinforcements, including tension rods, threaded bolts, and tie rods, have been integrated to replace traditional timber tension members, improving load capacity and reducing post bending in configurations like inverted queen post trusses used for structural repairs.[18] These adaptations allow for longer spans and greater efficiency within the design's typical limits. Modern fabrication relies on computer numerical control (CNC) machining to create precise mortise-and-tenon joints and asymmetric member sizing, enabling complex geometries that traditional methods could not achieve efficiently.[24] Prefabrication in factories has become standard, with trusses assembled off-site in pairs or full sections for quality control and rapid on-site erection.[18] This process minimizes waste and aligns with digital design tools for optimized cutting patterns.[25] Contemporary queen post trusses integrate with international building standards to ensure safety and performance, including the National Design Specification for Wood Construction (NDS) by the American Wood Council for material and fastener design values.[18] In Europe, Eurocode 5 governs timber structure design, incorporating provisions for notches and screws via Hankinson's formula to handle shear and tension.[18] For seismic zones, compliance with the International Building Code (IBC) and ASCE 7 requires assigning structures to seismic design categories based on ground motion severity, with steel reinforcements and glulam enhancing ductility and load resistance in high-risk areas.[26] The American Institute of Steel Construction's AISC 360 standard applies to steel components like knife plates in connections.[18] Sustainability drives recent revivals of queen post trusses through the use of Forest Stewardship Council (FSC)-certified wood, ensuring responsibly sourced timber that supports biodiversity and reduces deforestation, as offered by manufacturers like American Pole & Timber for custom truss production.[27] Recycled metals in reinforcements, such as steel rods from post-consumer sources, further lower embodied carbon, aligning with circular economy principles in projects emphasizing long-lasting, renewable materials over non-renewable alternatives.[28] These eco-friendly adaptations promote durability and renewability, with timber's carbon sequestration benefits making queen post designs viable for modern green building initiatives.[29]

Applications

In Roofing Systems

Queen post trusses are commonly employed in pitched roof constructions for residential barns and churches, where they provide essential support for collar ties and purlins that secure rafters and distribute loads to the underlying structure.[17][30] In these applications, the two vertical queen posts connect the tie beam to the principal rafters, enabling an open interior space beneath the roof while transferring roof loads effectively to the walls.[31] These trusses are particularly effective for low-pitch roofs with spans up to 22 feet, allowing for reduced overall roof height and minimized headroom requirements compared to steeper designs or alternative truss forms.[32] This configuration is advantageous in structures where vertical clearance is limited, as the queen posts help maintain structural integrity without necessitating excessive rise in the roof profile.[18] In 19th-century American vernacular architecture, queen post trusses featured prominently in New England barns, supporting expansive hay lofts and durable roof coverings in agricultural buildings.[17] Modern adaptations continue this tradition in timber-frame homes, where they are integrated into custom roof systems to achieve aesthetic vaulted ceilings and efficient load paths in contemporary residential designs.[33] Installation of queen post trusses in roofing systems involves precise positioning to align the vertical posts with key roof elements, such as valleys and hips, ensuring even support for intersecting rafters and preventing uneven stress distribution.[17] This alignment facilitates seamless integration with purlins and battens, enhancing the overall stability of sloped roof assemblies.[34]

In Floor and Ceiling Structures

In multi-story timber buildings, queen posts are adapted as vertical struts positioned beneath floor beams to provide intermediate support for joists, enabling longer spans without additional columns. This configuration transforms the traditional truss elements into a framing system where the posts connect to a horizontal tie beam or girder, with diagonal braces distributing forces to the supporting walls. Such adaptations allow for open floor plans by suspending joists from the truss assembly, distinct from inclined roofing applications.[11] Historically, this use appears in 18th-century structures, such as Vanbrugh's Foundry at Woolwich Arsenal, where a queen post truss supported an upper floor, demonstrating early industrial application for load-bearing needs. In Clandon Park in Guildford, queen post assemblies supported the ceiling over the main hall, and in the Queen's House at Greenwich, tie beams with queen post struts notched for ceiling joists provided stable suspension. These examples, often from the early to mid-18th century, illustrate the truss's role in creating suspended ceilings and floors in large halls and mills, akin to but separate from roofing parallels where vertical support counters thrust.[11] Queen posts in these floor and ceiling setups handle dead loads from flooring materials and live loads from occupancy, functioning as deep beams to span distances in historical applications, with the posts and braces mitigating sagging from shrinkage or creep, often secured by metal straps at the base to manage tensile forces.[11] In modern constructions, queen post variants appear in exposed-beam ceilings for lofts and open-plan spaces, combining structural reinforcement with aesthetic appeal in timber-framed homes and barns. For instance, they support second-floor structures in barns to create column-free areas below, allowing for flexible interior layouts while showcasing the truss's clean lines. These adaptations prioritize both functionality and visual integration, often using treated timber for durability in residential settings.[17]

Comparisons and Variations

Versus King Post Truss

The queen post truss differs from the king post truss primarily in its use of two vertical queen posts connected by a horizontal straining beam, in contrast to the single central king post of the latter design. This dual-post configuration in the queen post truss allows for enhanced structural support across wider areas, while the king post truss relies on a simpler, centralized vertical member to connect the apex of the roof to the tie beam.[35][32] Typical spans for queen post trusses range from 16 to 40 feet (4.9 to 12.2 m), enabling coverage of broader roof areas compared to king post trusses, which are generally limited to 16 to 26 feet (4.9 to 7.9 m). The queen post's design provides advantages such as greater span capacity and improved intermediate support, which facilitates more open space below the truss for architectural flexibility; however, it introduces added complexity in fabrication and assembly due to the additional members and connections. In contrast, the king post truss offers simplicity and lower material use but is less suitable for spans exceeding its limits without modifications.[2][36] Load paths in these trusses highlight further contrasts: in the king post design, forces are centralized and transferred directly downward through the single post to the supports, minimizing bending stresses in a straightforward manner. The queen post truss, however, distributes loads more evenly across the two queen posts and the intervening straining beam, which enhances overall stability for distributed roof loads but requires careful balancing to prevent uneven stress concentrations.[32] Queen post trusses are commonly applied in broader roof structures, such as those in commercial or larger residential buildings requiring spans beyond 26 feet, while king post trusses suit simpler, narrower applications like smaller homes or sheds where economy and ease of construction are prioritized.[35]

Regional and Hybrid Forms

In European architecture, the queen post truss developed distinct regional variants, particularly in England where it was commonly referred to as the "queen strut" form. This configuration featured paired vertical struts rising from the tie beam to a collar beam, often reinforced with angled braces to distribute loads effectively in vernacular roof structures without relying on longitudinal timbers. Such designs were prevalent in medieval and early modern buildings, evolving from earlier medieval forms with arch braces to more refined 17th- and 18th-century iterations incorporating metal straps and joggles for enhanced stability.[37][38][11] French adaptations of the queen post truss emphasized lighter timbers and steeper roof pitches, integrating side purlin systems over principal rafters, which influenced grand timber frames in chateaus and similar structures. These variations, as seen in works inspired by architects like Le Muet, allowed for expansive spans in attic roofs and theaters, with external trussing resembling queen post elements to support elaborate designs while adapting to local material availability and aesthetic preferences. Early examples, such as those in Jousse's 1627 Theatre de Charpenterie, demonstrated girders trussed externally in ways akin to queen posts, marking a shift toward more engineered forms in continental Europe.[11] In North American forms, particularly during the colonial period, queen post trusses were used in barn roofs to provide support for agricultural structures using locally sourced timber, as documented in historic American roof truss analyses.[39] Asian influences on queen post trusses remain rare but appear in hybrid timber frames during post-World War II reconstructions, notably in Japan where Western truss principles were blended with traditional post-and-beam systems. In these adaptations, queen post-like vertical elements supported hybrid roofs over reinforced concrete bases, facilitating rapid rebuilding of public and residential structures while incorporating earthquake-resistant features and local wood species. Such designs emerged in the mid-20th century amid resource constraints, combining truss efficiency with indigenous joinery techniques for enhanced versatility.[40] Modern hybrids of the queen post truss often integrate elements from Fink trusses to achieve longer spans in commercial buildings, adding diagonal web members in a W-pattern between the queen posts for improved load distribution. This combination allows spans exceeding 30 feet while maintaining the aesthetic appeal of exposed timber, commonly applied in retail spaces, warehouses, and event halls where open interiors are prioritized. These innovations draw on historical forms but employ engineered modifications for contemporary performance requirements.[41]

References

  1. Queen Post Truss: All You Need to Know - GharPedia
  2. Queen Post Truss in Construction: Design, Components & Benefits
  3. Truss - Queen Post Dimensions & Drawings
  4. FHWA-HRT-04-098-Chapter 4. Types of Longitudinal Trusses ...
  5. What is a Truss Bridge - TN.gov
  6. [PDF] Queen-Post-Truss Timber Bridge - Iowa State University
  7. [PDF] Simplified Analytical Model for a Queen-Post Covered Timber Bridge
  8. Encyclopaedia of English Medieval Carpentry | G-L
  9. [PDF] KEY DATING FEATURES FOR TIMBER-FRAMED DWELLINGS IN ...
  10. The Hammer-beam Roof of Westminster Hall and the Structural ...
  11. The Project Gutenberg eBook of English Church Architecture of The ...
  12. [PDF] The Origins of the King and Queen Post Roof Trusses
  13. Timber Framed Buildings and Roofs - Building Conservation Directory
  14. [PDF] The Charleston Trussed Roof - Clemson OPEN
  15. Medieval Roof Trusses in Sweden – New Perspectives on Wooden ...
  16. [PDF] The Historic Belfast Timber Truss - A Way To Promote Sustainable ...
  17. A. W. N. Pugin: Master of Gothic Revival | A&AePortal
  18. Divine Design: Renovating and Preserving Historic Houses of Worship
  19. [PDF] Rehabilitating a Historic Truss Bridge Using a Fiber Reinforced ...
  20. [PDF] TFEC 4 – 2020 Design Guide for Timber Roof Trusses
  21. [PDF] Design Guide for Timber Trusses - Carolina Timberworks
  22. Timber Frame Trusses Guide - Carolina Timberworks
  23. 6.4 Method of Joints - Engineering Statics
  24. Wood Truss Failures: Typical Failure Modes - Robson Forensic
  25. Construction Process of a Timber Frame: Wood Drying
  26. [PDF] The'Timber Framing ,Rook II - United Diversity Library
  27. Essential Truss Types for Efficient Residential Construction | StruCalc
  28. How Prefabricated Wood Trusses Reduce Construction Waste and ...
  29. 2018 International Building Code (IBC) - 1613.2.5 Determination of ...
  30. FSC Certified® Timber Trusses Now Available
  31. Timber or steel? Study helps builders reduce carbon footprint of ...
  32. Timber Frame Trusses 101: Benefits, Styles & Design Tips
  33. The Collar Tie with Queen Post Truss - Harmony Timberworks
  34. What Is a Queen Post Truss? 2025 Latest Guide
  35. [PDF] Alpine Roof Truss Guide 07111...
  36. Queen Post Truss | Homestead Timber Frames
  37. Queen Post Roof Trusses
  38. King Post Trusses vs Queen Post Trusses | BeamCut
  39. Queen strut - Vernacular Building Glossary
  40. [PDF] KEY DATING FEATURES FOR TIMBER-FRAMED DWELLINGS IN ...
  41. Timber Framing | Timber Framers Guild
  42. [PDF] World War II
  43. Innovative Roof Truss Design Strategies for Modern Construction
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