Pergolas are a great way to add a little flair to your backyard. It allows you to enjoy being outdoors while providing protection from the elements.
The tricky thing, however, is figuring out how far a pergola can span. This is vital information, especially if you’re a DIYer and plan on building it yourself.
So, how far can a pergola span?
Keep reading this article to learn about the spanning length of different beam sizes and the variables that affect the distance.
There isn’t a definite answer to how far a pergola spans. However, several factors play a role in determining how far a pergola can span; including:
- The type of material used: steel, lumbar, PVC, vinyl, or fiberglass
- The size and grade of the lumber
- The weight load, such as the snow load
- The deflection limits of beams
- Local guidelines and codes
A 2×4 piece of lumber used for a pergola ceiling can go a linear distance between 4 to 6 feet, depending on the quality of timber used and the spacing between the ceiling joists.
You could use 2×4 beams and rafters to build a small shed pergola. What’s more, 2×4 ceiling joists can make excellent headers above doors or anywhere you need a small outdoor extension.
That said, the 2x4s are generally used as louvers. Louvered pergolas are a great way to provide shade and protection from various weather conditions compared to just beams and rafters.
You can use a 2×6-sized piece of timber to span a pergola for around 8 to 10 feet.
However, that primarily depends on the grade of wood used. The maximum span will also depend on the spacing between the support structures used to make the pergola.
If you’re using softwood such as pine wood, then the span length will be shorter than if you were using hardwood, like oak. That’s because the less durable the timber, the more likely it’ll sag over time when used for long spans.
For a maximum span using 2×6 joists, you want to use timbers of durability class 1 or 2. Timber durability classes range from 1 to 5, with the former featuring the highest durability and a life expectancy of more than 25 years. Class 5, on the other hand, is the lowest in durability and has a life span between 0 to 5 years.
The distance between beams and rafters can also impact the pergola span. Not only is accurate spacing crucial for proper support, but it can also help increase the spanning distance.
Usually, spacing is measured from the center of the beam or rafter to the center of the adjacent piece of timber.
Anywhere from 12 to 24 inches are standard spacing for the rafters. Yet, keep in mind that the closer the spacing is, the farther you can span the pergola.
However, the spacing won’t increase the pergola spanning as much as you’d think.
For example, a 2×6 pergola stretching 24 inches from the center can reach around 8 feet. On the other hand, when you space the rafters at 12 inches from the center, they can span up to 10 feet.
Yes, you can use 2×6 lumbers to build a pergola. However, it depends on the measurements and structure of the pergola itself.
If you plan on covering a large area that spans more than 10 inches, then 2×6 rafters and beams may not be adequate. For starters, the timbers will most likely droop from the middle.
In addition, using 2×6 timbers may work well for building an open-roof unit. However, for a closed roof system, you won’t be able to use 2×6 beams and rafters.
That’s because closed-roof systems must withstand at least 20–30 pounds of snow per square foot. Thus, 2x6s for closed roofs may not bear the load of heavy snowing.
You should also take into account the dead load of the ceiling, which is the permanent load from the weight of the structural components combined. This is another factor to help know whether or not it’s safe to use 2×6 for the pergola.
As a general rule of thumb, 2×8 beams and rafters can span from 12 to 13 feet. One way to measure the maximum span is to use the American Wood Council Span Calculator.
The thicker and sturdier the wood used, the longer you can increase the span. However, keep in mind that the sturdiness of the wood differs depending on whether it’s seasoned or not.
Also, natural timber contains high moisture content, which softens the wood and makes it susceptible to breakage and fungal growth. In contrast, seasoning the wood removes as much water content, making it stronger and suitable for long pergola spans.
Generally, 2×10 rafters and beams can span 16 feet in length. That said, it’s possible to increase this spanning length by bracing the timbers.
Providing the timbers with extra support at the corners or attaching metal plates to the posts and beams helps reinforce the structure. Consequently, you can increase the overall pergola size.
What’s more, adding extra support posts at the edges and center of the pergola will make it sturdier and also increase its span. Yet, it disrupts the flow of the space, so if you prefer a more uninterrupted span, pot for steel, PVC, or fiberglass to support longer extensions.
Using 2×12 for pergolas will give you the largest span of 20 feet. The distance can increase a couple of feet when using grade 1 wood and maintaining smaller spacing.
Similar to standard pergolas, cantilever pergolas can span about 20 feet, but it mainly depends on the design, beam length, load, and materials used.
Generally, any beam length can be used to project a cantilevered pergola. However, it needs sufficient depth and proper reinforcement to support the hanging structure and increase span length.
So, how far can a pergola span?
Small timber sizes 2×4 and 2×6 can span 6 and 10 feet, respectively. Alternatively, larger beam sizes like 2×10 and 2×12 reach longer linear distances of 16 and 20 feet.
That said, you should always check with the local guidelines to determine how far you can span your pergola.
Ben has a bachelor’s degree in construction engineering. When not constructing or remodeling X-Ray Rooms, Cardiovascular Labs, and Pharmacies, you can find him at home with wife and two daughters. Outside of family, He loves grilling and barbequing on his Big Green Egg and Blackstone Griddle, as well as working on projects around the house.
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