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How Far Can a Roof Truss Span Without Support? (Answered)

A few weeks back, I saw my neighbor was building his house with a roof truss to support the roof. The roof truss was long, and I wondered why he didn’t put any support over there. Then I asked him and came to know the actual science behind it.

A roof truss is a timber-made support for the roof. Some people use the support; some don’t. Does it matter anymore?

We will look at the fact and discover how far you can span it. Some factors influence the spanning of the rooftop; we will talk about them in today’s write-up.

How far can a roof truss span without support?

A roof truss can span around 80 meters without support. If you want to span it more, you will need to support it. An Eighty-meter span is more than enough for a typical house. It will support the rooftop pretty well—types of truss, snow load, and other factors influence the spanning.

When you give support to the roof truss, you can span it more than 100 meters, which is unnecessary for most people.

It will be better to focus on the quality of the truss and use better wood or timber here. Besides, the roof slope also plays a vital role in spanning the roof truss.

You have to balance these factors and ensure the best quality to best span the roof truss without support.

But the 80 meters spanning will be a costly framework, and you may not need that much support from the roof truss. Therefore, the 40-meter roof truss spanning is primarily standard.  

2×4 roof truss span:

A 2×4 roof truss can span around 41 meters if it builds to support 55 pounds of snow per square foot.

If you plan to build the 2×4 roof truss for 40 pounds of snow load per square foot, it will span 46 meters without any support. The quality of the roof truss will allow it to span; that’s why it doesn’t need any support.

People mostly don’t go for support since they don’t need more. However, the 55 pounds of load per square foot is enough for a typical house beside the street. If you plan to build a home somewhere else, you can use the support.

2×6 roof truss span:

When you have a 2×6 roof truss framework, it will span around 10 feet 9 inches.

You need to count this spanning from beam to beam, where the live load will be 30 inches per square foot. It is the maximum live load for a 2×6 roof truss.

What are the standard roof truss sizes?

The standard roof truss sizes are 32 meters. In most US buildings, you will find the roof trusses are below 40 meters.

They don’t need bigger roof truss sizes since they can span up to 80 meters without external support. Buildings have a 2×4 roof truss span to get the best standard roof truss spanning.

It is the standard size as well. You don’t need to go for the 2×6 roof truss span. It might go below standard and not bear the load in heavy snow. So, it’s better to go for the roof truss, which can hold 55 pounds per square foot.

What is the standard spacing for roof trusses?

The standard spacing is 24 inches for roof trusses on centers. But it can be 12 or 16 as well. These three are considered standard, but the engineer takes 24 inches as the standard spacing for the roof truss.

Among these three standard spacing, you don’t need to use any heavier duty fasteners at all. The roof truss can span itself without any support. And, it will be enough for your house and the roof support.

What are the factors that affect the roof truss span?

Typically the four factors affect the roof truss span. The size of lumber, the Slope of the roof, snow loads, and the truss type are the four factors that ultimately affect the roof truss span.

Size of Lumber:

Generally, 2×4 or 2×6 is considered the standard size of the lumber or timber. It will help the roof truss span most securely. However, you can also consider using the 2×8 lumber size if required.

It will be better to discuss the lumber size with your engineer. He can advise you since other factors also affect the roof truss span.

The Slope of the roof:

The standard Slope of most roofs is between 4/12 or 9/12. Anything less or more is not ideal for the roof truss span. You will get the 4/12 slope on most of the roof, which supports the roof truss most.

Anything more than the 9/12 is considered as the steep slope roof. It is not ideal for most houses; it might not support the span of the roof truss-like the standard one.

Snow loads:

One single factor that can affect the roof truss span most is the snow loads.

For instance, if the snow load per square foot is 55 pounds, the roof truss can span up to 41 meters. The same roof truss can span 46 meters if the load is 40 pounds per square foot.

So, it’s better to calculate the snow load first and then select the right limber size for your house. You can either go for the 2×4 or the 2×6 lumber size to support the snow loads accordingly.

Type of truss:

You will find more than five truss types available for your rooftop. You can go for the required one.

But the kinds of truss also play a significant role in spanning the roof truss. So, before selecting the truss type, try to know all the available types.

Don’t hesitate to spend some extra bucks on quality trusses. It will be your longtime investment to secure the rooftop. Especially if you live in a high snowfall area, you must consider buying quality trusses.

How to calculate maximum roof truss span?

DIYer can’t calculate the maximum roof truss span without prior experience or knowledge about it. But there are some simple ways that you can follow to calculate the rafter span or find out the maximum roof truss span.

To calculate the maximum roof truss span, you need to divide the external width of the walls by two. Moreover, you can divide the rafter span by Cos degree (the Slope)

Do roof trusses need support in the middle?

Roof trusses don’t need any support in the middle or the center. If your house has 2×4 or 2×6 lumber size, you don’t need any kind of central support. It can bear a load of snow up to 55 pounds per square foot.

When you want to build a factory or an enormous industry to manufacture the products or for big business, you can use the central support for the roof truss.

But here you are planning to build your house, and it is smaller than the big factory, that’s why you don’t need any support for the roof truss.

How are conventional roof and truss roof supported?

Different ways support the conventional roof and the truss roof supported. A conventional roof is a typical rooftop with a lower slope than the truss roof.

Conventional roof:

Conventional roof is supported by rafters. It supports and maintains the weight of the entire rooftop. You can use different sizes of the rafters according to your house length and width.

You should calculate the length of the rooftop first. Then you can decide the rafter size. It will be better to measure the best rafter size to support the conventional roof.

Truss roof:

The combination of timbers and plates support the truss roof. Mainly, the truss roof has more slope angles.

Therefore, it needs support from the surroundings. In that case, the timbers and the plates from around the truss roof will support it.

Here the timbers play a vital role. It supports the truss roof and maintains slope angle as well. Top and bottom chords are also there to support the truss roof.

What is the maximum distance between roof trusses?

Twenty-four inches is the maximum distance between the roof trusses. But it can be 12 or 16 inches as well. The distance will depend on the frame structure.

If you want to ensure a safe distance between the roof trusses, you can make a 16 inches’ distance between them.

You can also secure the truss roof by connecting all the trusses without maintaining any distance. It’s better to follow a standard rather than connect them all.

Final thoughts

The maximum span of the roof truss depends on four factors. Typically, the standard span is between 40 and 46 meters. In general, the roof truss can span about 80 meters without any support. If you want to build a large house or building, you can use the support and enlarge the distance.