Metal Roof Purlins Spacing and Rafter Distance Details

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During the roof installation or re-roofing process, after the roof sheets are prepared it is time to support their framework by installing purlins. The structure of purlin helps to shift some of the loads that put on the metal sheeting to the main building construction, by ensuring that the whole things stay in their place and adding structural integrity.

If you are currently involved in this type of project and want to know metal roof purlins spacing, you can use the passage below as reference to get the task done properly.

Metal Building Purlin Spacing

Metal roofs are often referred as tin roofs in the past because of the use of tin, such as aluminum or stainless steel sheets as the materials. Compared to conventional roofing system, it might be a bit pricier in terms of installation, but also has longer durability to provide better value for the future.

Metal Roof Purlins Spacing

Metal panels has great resistance to bugs and fires, to the extreme condition such as snow, wind, and storm. They are also popular for the people who like to install the roof themselves, because the process is easier.

Setting corrugated metal roof purlin spacing in a proper distance is an important part of the entire process. The distance lengths are often based on the roofing panels’ size. Proper spacing will offer attachment security that resulted in optimal stability. However, if your metal roof has another supporting method, the exact spacing is not needed most of the times. 

To check the correct purlin spacing standards, it is better if you read the manufacturer’s installation manuals. It often depends on the wideness, thickness, and the types of roofing materials, the climate it has to withstand, and many other factors. For the lighter material such as lightweight aluminum, the common spacing length is 4 inches of clear gap.

For heavier material such as gage steel, the metal roof purlins spacing length could go up to 4 feet. The typical spacing standards for residential and commercial buildings are about 1 to 2 foot.

The support system for the roof is comprised of ridgepole and rafters or purlins. With rafters, it runs in perpendicular from the walls to the ridge, while with purlins, it runs to the ridge in parallel. Using a combination of rafters and purlins is common.

This arrangement offers support for the roof, adds interior aesthetic if you opt to match the rafters and purlins with the wall logs. It is especially preferable to use in huge room that lacks trusses, to create overhead effect, despite the fact that trusses are used for practical purpose in the first place.

Purlins might be attached to rafters, while rafter should support all laps and joins. The rafter and purlin spacing for metal roof must be fitted to support the whole framework.

rafter and purlin spacing for metal roof

It is important to do inspection before you continue with the installation project: to check if the framework is properly leveled and aligned, if there are adjustments that needs to be created, and so on. The metal roof purlins spacing must be done correctly within narrow tolerances. There is a chance of damaging roofing sheets if you are failed to do so.

The width of metal panels will determine the rafter spacing. The wider the roofing panels, the greater spacing distance you should put. You have to allow some overlap section on each side of the metal, but it will decrease the panel’s effective width.

Determining rafter’s spacing is as important as setting the metal roof purlins spacing. You have to take the width of your roofing panel into the considerations. The most common measurement used for rafter spacing is either 16 or 24 inches.