**What size purlin for 3m, 4m, 5m, 6m & 8m span | what size purlin to span 20 feet | What size purlin to span 30 feet | what size purlin for 5m span | what size purlin for 6m span | what size purlin for 4m span | what size purlin for 8m span**.

In the field of architecture, structural engineering or building, a purlin or historically known as purline, purloyne, purling, perling is a horizontal beam made of wood or either steel used for structural support in buildings, most commonly in a roof. It take all the load coming from roof sheets, rafter and withstand with and safely vertically downward transfer to stud or posts.

Steel or wood Purlins are supported either by rafters or the walls of the building in frame structure. They are most commonly used in metal buildings, though they sometimes replace closely spaced rafters in wood frame structures also. Purlin comes in different types and sizes and having different installation such as single span system in which one purling span the length of a structure and double purling span system two purlin are supported at the end and in the centre. It comes in different types and sizes therefore it is important for you to use the right size purlin.

Generally purlin are made of steel or wooden frame structure. If you want more breathable environment inside your room then you should select wood material for purlin. This allows someone to store organic material inside room such as grain and livestock.

You have another option to select purlin made of steel. Steel purlin is a lightweight, straight, stable and more accurate. Steel purlin can be withstand in change of temperature by expansion and contraction. Steel purlin are usually manufactured with galvanized steel coated with zinc to provide rust protection and finally it can be finished with paint.

In this article you know about what size purlin for 3m, 4m, 5m, 6m & 8m span, what size purlin to span 20 feet and what size purlin to span 30 feet that will help you in better understanding and to figure out or estimate of purlin size and their depth and help in important for you to use the right size purlin.

**What size purlin for 3m, 4m, 5m, 6m & 8m span**

The standard sizes for purlins are produced in nominal depth of 100mm (4 inches),150mm (6 inches), 200mm (8 inches), 250mm (10 inches) and 300 mm (12 inches). The spacing between purlins depend on the type of roof cover used and their thickness as function of purlins is to carry roof cover sheet and safely transfer the load they carry to trusses, therefore the dimension of the roof cover determines their spacing. Normally a spacing of purlin is around 1400mm (1.4m), it can be spaced 1.2 metres apart when using sheeting with a thickness of 0.7mm, and 1 metre when using 0.5mm sheeting. Exact requirements will vary, but as a rough guide, this is a good rule of thumb to follow.

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**What size purlin for 3m span**:- as general guidelines and rules, generally you need a 100 mm (4 inches) size of purlin for 3m or 10 feet span. Thus a 4 inch depth of purlin is most suitable for 3m or 10 feet span which can safely transfer the load they carry to trusses.

**What size purlin for 4m span**:- as general guidelines and rules, generally you need a 150 mm (6 inches) size of purlin for 4m or 13 feet span. Thus a 6 inch depth of purlin is most suitable for 4m or 13 feet span which can safely transfer the load they carry to trusses.

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**What size purlin for 5m span**:- as general guidelines and rules, generally you need a 150 mm (6 inches) size of purlin for 5m or 16 feet span. Thus a 6 inch depth of purlin is most suitable for 5m or 16 feet span which can safely transfer the load they carry to trusses.

**What size purlin for 6m span**:- as general guidelines and rules, generally you need a 200 mm (8 inches) size of purlin for 6m or 20 feet span. Thus a 8 inch depth of purlin is most suitable for 6m or 20 feet span which can safely transfer the load they carry to trusses.

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**What size purlin for 8m span**:- as general guidelines and rules, generally you need a 250 mm (10 inches) size of purlin for 8m or 26 feet span. Thus a 10 inch depth of purlin is most suitable for 8m or 26 feet span which can safely transfer the load they carry to trusses.

**What size purlin to span 20 feet**:- as general guidelines and rules, generally you need a 200 mm (8 inches) size of purlin to span 20 feet. Thus a 8 inch depth of purlin is most suitable for 20 feet span which can safely transfer the load they carry to trusses.

**What size purlin to span 30 feet**:- as general guidelines and rules, generally you need a 250 mm (10 inches) size of purlin to span 30 feet. Thus a 10 inch depth of purlin is most suitable for 30 feet span which can safely transfer the load they carry to trusses.

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**How far can a 4 inches purlin span**:- as general guidelines and rules, generally a four inch size of purlin can span 12 feet. This is maximum allowable span for 4 inch size purlin which can safely transfer to the trusses.

**How far can a 6 inches purlin span**:- as general guidelines and rules, generally a six inch size of purlin can span 18 feet. This is maximum allowable span for 6 inch size purlin which can safely transfer to the trusses.

**How far can a 150mm C purlin span**:- as general guidelines and rules, different gradation and weight, a 150mm (6″) thick C purlin can allow span upto 5.5m to 8.7m far distance when spaced 1200mm at centre to centre and wind velocity of 33 m/s. Thus 150mm C purlin will allow to span 5.5m to 8.7m far. Thus a 150mm depth of C purlin is most suitable for 5m to 8m span which can safely transfer the load they carry to trusses.

**How far can a 8 inches purlin span**:- as general guidelines and rules, generally a eight inch size of purlin can span 25 feet. This is maximum allowable span for 8 inch size purlin which can safely transfer to the trusses.

**How far can a 10 inches purlin span**:- as general guidelines and rules, generally a ten inch size of purlin can span 30 feet. This is maximum allowable span for 10 inch size purlin which can safely transfer to the trusses.

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**Conclusions**:

As per generals rule and guideline, you need a 4- inch (100mm) purlin for 3m span, 6- inch (150mm) purlin for 4m & 5m span, 8- inch (200mm) purlin for 6m & 10- inch (250mm) purlin for 8m span which can safely transfer the load to trusses.