A purlin used in steel building construction

Purlin appears in steel frame construction, they are an essential part of any building’s structure, providing support and stability to the roof and walls. Both Z and C purlins serve the same purpose. They are fixed to the portal frame, and it typically refers to roof or wall steel framing components that support the weight of the roof steel sheet or wall panel. Steel purlins are mostly made of galvanized.

C purlin and Z purlin are most commonly used in mtal buildings, like warehouses, workshops, storage, poultry farm sheds, etc. 

C purlin is formed in the Shape of “C”, and all angles of a C purlin are 90 degrees, while Z purlin is formed in the shape of a “Z”, not all angles of a Z purlin are at 90 degrees. They differ in their shape and structural properties. C purlin and Z purlin are made from galvanized steel and are roll-formed to length with holes punched to your specifications and requirements.

Sizes Available for C Purlins: 

C Channel	Model	Section size
		h（mm）	b（mm）	a（mm）	s（mm）
	C100	100	40	20	1.6 - 3.2
	C120	120	40	20	1.6 - 3.2
	C120	120	50	20	1.6 - 3.2
	C120	120	60	20	1.6 - 3.2
	C140	140	50	20	1.6 - 3.2
	C140	140	60	20	1.6 - 3.2
	C160	160	50	20	1.6 - 3.2
	C160	160	60	20	1.6 - 3.2
	C180	180	60	20	1.6 - 3.2
	C180	180	75	20	1.6 - 3.2
	C200	200	60	20	1.6 - 3.2
	C200	200	70	20	1.6 - 3.2
	C220	220	60	20	1.6 - 3.2
	C220	220	70	20	1.6 - 3.2
	C240	240	70	20	1.6 - 3.2
	C240	240	75	20	1.6 - 3.2
	C250	250	75	20	1.6 - 3.2
	C260	260	75	20	1.6 - 3.2
	C280	280	80	20	1.6 - 3.2
	C300	300	100	20	1.6 - 3.2
	C320	320	100	20	1.6 - 3.2
	C340	340	110	20	1.6 - 3.2
	C350	350	120	20	1.6 - 3.2

Sizes Available for Z Purlins:

Z Channel	Model	Section size
		h（mm）	b（mm）	a（mm）	t（mm）
	Z100	100	40	20	1.6 - 3.2
	Z120	120	50	20	1.6 - 3.2
	Z120	120	60	20	1.6 - 3.2
	Z140	140	50	20	1.6 - 3.2
	Z150	150	60	20	1.6 - 3.2
	Z150	150	60	20	1.6 - 3.2
	Z160	160	60	20	1.6 - 3.2
	Z160	160	70	20	1.6 - 3.2
	Z180	180	60	20	1.6 - 3.2
	Z180	180	70	20	1.6 - 3.2
	Z200	200	60	20	1.6 - 3.2
	Z200	200	70	20	1.6 - 3.2
	Z220	220	60	20	1.6 - 3.2
	Z220	220	70	20	1.6 - 3.2
	Z240	240	60	20	1.6 - 3.2
	Z240	240	75	20	1.6 - 3.2
	Z250	250	75	20	1.6 - 3.2
	Z300	300	100	20	1.6 - 3.2
	Z350	350	120	20	1.6 - 3.2

Differences Between C And Z Purlin:

1. Application

C Purlins can be used for the walls and floor joists of a building shell structure and they are ideal for support beams for mezzanine flooring. They can also be used for door frames, roof trimming, window trimming, and parapet framing. Z Purlins are used for a building shell structure's roof and wall joists. They sit between the steel sheets and the steel building frame, acting as a support for the corrugated steel sheets to ensure it is firmly attached and safely in place.

2. Connections

C purlins have similar extensions on their ends, that can not be overlapped, meaning that they are more suitable used in single spans. While Z steel purlins can be overlapped continuously. Therefore, Z purlin is much stronger than C purlin. It's better to use Z steel purlins for metal buildings with bigger roof loading capacity or continuous spans.

3. Roof slopes

If a roof slope is small, C purlin may be a feasible choice for the steel building, because the section of Z purlin is slightly too large for a small slope. If the roof slope becomes large, the section of Z purlin will also increase vertically, which means the arrangement of Z purlins can better support the roof load and maintain the stability of the structure. In this case, Z purlins are better suited for large slope roofs.

4. Installation

Compared with Z purlins, C purlins are easier to install, they require minimal effort and skills. Usually, they are used on single-span roofing structures. While Z purlins need more effort and additional expertise for roofing system installation. 

Steel building project picture for purlin Installations

Z purlin

C purlin

The advantages of purlins in steel prefabricated building are obvious:

• ● Flexibility in the length design and construction of roofing structures.
• ● Cutting to the required dimensions and punching holes in factory, less on-site works.
• ● High tensile strength can withstand heavy loads and provide stability to the wall and roof.
• ● Galvanized steel, which have a high resistance to corrosion ensures the durability.
• ● Easy Installation, saving time and effort during the construction process.