Where a King post uses one central supporting post, the Queen post truss uses two. A Queen post truss carries all the load from its rafters and passes it to the vertical posts.
The King Post Truss is configurable in a range of sizes with typical spans between 16'-26' (4.9-7.9 m) and overall heights of 2'8”-13' (. 81-3.96 m). The thickness of wood trusses is commonly 1.5”, 3”, or 4.5” (3.8, 7.6, 11.4 cm). Trusses have a pitch ratio typically between 1:1 to 1:6.
King post trusses are advantageous because they are cost-effective, straightforward to construct, and versatile for different building types. However, their main disadvantage is that they are suitable for shorter spans compared to other truss types due to the limit in structural efficiency over larger distances.
A king post extends vertically from a crossbeam (the tie beam) to the apex of a triangular truss. The king post, itself in tension, connects the apex of the truss with its base, holding up the tie beam (also in tension) at the base of the truss.
(iii) King Post Truss - Span length is in the range of 5 to 8 meters. (iv) Queen Post Truss - Span length is in between 8 to 12 meters. (v) Pratt Truss - Span length is in between 6 to 10 meters. (vi) Howe Truss - Span length is in between 6 to 30 meters.
The primary difference between the two is that a king post truss has a single supporting post and a queen post truss has two. Applications of each depend on the size of the roof span, with king post trusses spanning 5 to 8 meters. Due to the double posts, queen post trusses have a wider span, measuring 8 to 12 meters.
Truss count = ((roof length * 12) / 24) + 1
The simplest form of this equation is to take the length of your roof and divide it by 2. For example, if your roof is 40-feet long, it will need a total of 20 trusses.
When properly constructed with tight-fitting, precisely cut joints, the through-tenon King Post Truss provides a sturdy roof structure. The forces follow a clear load path - down the rafters, into the king post, through the tenon, and into the tie beam.
The king post truss uses principal rafters, common rafters, purlins, battens, a tie beam, king post, and struts to support roofing materials like mangalore tiles and form a sloped roof at an angle of 1 in 2.
One of the key benefits of king post walls is their fast installation since they are pre-cast. Aside from being cost-effective, this retaining wall is very versatile. It is the best option for challenging grounds, and they are silent and vibrationless.
The king post truss is one of the strongest designs and can support very heavy loads. It consists of two vertical posts connected by a horizontal beam at the top. 2. The queen post truss is similar to the king post truss, but it has an additional beam running between the two vertical posts.
It is a combination of king-post and queen post trusses. The mansard truss is a two-story truss with the upper portion consisting of a king post truss and a lower portion consisting of a queen post truss.
Trusses cost more because they use the same amount of material, but you'll also be paying for the labor, as well as the delivery to your home. However, if you're having a contractor build the roof for you, then trusses will be less expensive, as the labor costs to build roof framing on-site will cost more.
While there are several advantages to using a king post truss, there are also some potential disadvantages that should be considered: Limited span: King post trusses have a relatively limited span, so they may not be suitable for larger buildings or spaces requiring longer spans.
King posts are isolated steel columns or beams that are installed along the line of the proposed retaining wall typically at centres between 1 and 3m. The space between the posts is filled, over the retained height, using a variety of different solutions but most commonly a precast concrete panel.
In king post truss, purlins are supported by the principal rafter. The purlins support the closely spaced common rafters. The slope of common rafters is same as that of the principal rafter. The common rafters support the roof covering.
The maximum span that a king post truss with 6"x6" Douglas Fir posts can support is 32 feet, assuming a dead load of 20 psf and a snow load of 40 psf. If you increase the snow load to 50 psf, the maximum span decreases to 28 feet. If you want to support a span of 40 feet, you will need to use larger posts.
Components of a King Post Truss
1. Rafters: These are the sloping members of the truss work design that form the triangle's sides. They bear the roof load and transmit it to the vertical king post. 2. King Post: This is the vertical central member, which runs from the tie beam at the bottom to the apex of the triangle.
Span: The King Post Truss is ideal for spans of 5-8 meters (16-26 feet), making it suitable for small to medium-sized roofs. Shape: It forms a triangular structure, with the King Post being the vertical element in the middle.
A king post truss, or turkey track truss, is built with two principal rafters, a tie beam, a central vertical post, and two struts. The central vertical post is what gives the king post truss its triangle shape. For added support, one strut is placed at a 45° angle on each side.
A good thumb rule for the truss spacing is 1/5 to 1/3 of their span. The depth of a truss determines its strength, stiffness, its first cost and the cost of transportation to the site and subsequent erection.
Cedar is a popular choice for its balance of beauty, durability, and resistance to decay. Fir and cypress are great alternatives for those prioritizing cost and weather resistance.
The vast majority of trusses utilize 2x4 dimensional lumber but webs can vary from 2x3 up to 2x12 lumber depending on the design. The grade and species of lumber used for webs is typically different from the chords of the truss to drive economic efficiency.
For Example: Calculate the length of the maximum height of the king post in a roof truss to ensure that the slope of the roof is less than 10°. The width of the house will be 40 feet. 40ft tan 8 = opp adj X tan 10° 20 ft 20 ft • tan 10° = x x = 3.52 ft Therefore the king post should be no longer than 3ft 6in.
The formula is truss count = ((roof length × 12)/24) + 1 . This equation will help you determine how many trusses your roof needs. For example, if your roof is 30 feet long, you will need 16 trusses.