What are the advantages of a king post?

Author: Dr. Lawrence Harris  |  Last update: Friday, July 18, 2025

King posts are cost-effective at retaining soil or earth, and builders use them temporarily or permanently. In construction projects where the workers cannot use sheet piles due to the hardness of the ground, they drill the ground to insert posts at pre-determined centres.

What is the use of king post?

A king post (or king-post or kingpost) is a central vertical post used in architectural or bridge designs, working in tension to support a beam below from a truss apex above (whereas a crown post, though visually similar, supports items above from the beam below).

What are the disadvantages of king post trusses?

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.

When to use king post?

Despite their simple structure, Kingpost prefabricated trusses can be used for a variety of purposes. Their suitability to span up to 4 metres makes Kingpost trusses a favourite for use in the construction of small house extensions, garages, garden sheds and dormer windows.

What are the characteristics of a king post truss?

A King Post truss embodies the essence of traditional timber trusses. This type of truss has been used for hundreds of years to support roofs. Featuring a triangular structure formed by a base tie beam and two sloping rafters, the central post adds support from the apex to the tie beam's centre.

King Post Truss vs Queen Post Truss

What is the advantage of king post truss?

The main advantage of king post trusses is their simplicity, making them cost-effective and easy to construct. However, their limitations include reduced load-bearing capacity compared to other truss types and limited span capabilities.

How far can a king post truss span?

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' (.

What is the load path of a king post truss?

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.

What is the difference between a king post and a queen post?

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. Even though it is a tension member, rather than a compression member, they are commonly still called a post.

What is the difference between king post and soldier pile?

King Post Walls, also known as Soldier Piles, are some of the oldest forms of retaining systems used in deep excavations. They have successfully been used since the late 18th Century in metropolitan cities like New York, Berlin, and London.

Can you mix rafters and trusses?

Can I use both trusses and rafters together? Yes, you can create a hybrid roof system that incorporates both rafters and trusses. This approach allows you to combine the design flexibility of rafters with the structural efficiency of trusses in specific sections.

What is the angle of a king post truss?

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.

Is it cheaper to build or buy roof trusses?

There are several reasons: Roof trusses are built in volume, allowing truss manufacturers to take advantage of bulk discounts on raw materials. Contractors often cannot access these types of discounts, making it more cost-effective to buy pre-made trusses. Roof trusses save time in labor.

What is the spacing of king post?

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.

What is the economical span range for the king post 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.

What is the alternative to sheet piling?

TrapBag barriers are superior to traditional metal sheet piles for construction retaining walls due to their versatility and ease of installation.

What is the purpose of a king post?

King post: This vertical post stands at the centre of the truss and supports the structure's weight. The king post is typically made of wood and is the main load-bearing element of the truss.

What are two advantages of a queen post?

Because queen posts are simple in design, they don't put any weight or load on the centre of the tie beam, unlike king post trusses. They're also a cost-effective option and area-effective fit for a wide range of roof sizes.

What is the best wood for roof trusses?

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.

What is the thumb rule for truss design?

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.

How to determine the height of a kingpost?

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.

How far can a 2x10 span without support?

2x4 11'-6" 2x6 17'-0" 2x8 21'-8" 2x10 25'-7" 24" O.C.

How many trusses for a 30x30 garage?

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.

What is purlin for?

A metal purlin is a lightweight, horizontal beam or bar that is used for structural support in roofing. In addition to providing support, metal purlins also increase a building's resistance to heavy winds. Purlins are a key component to the secondary frame of commercial, residential and industrial metal buildings.

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