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How Far Can a 2×8 Span Without Support? (Read This First!)

Are working on the construction of your house? Are you wondering how far a 2×8 can span without support? 

Additionally, are you also facing difficulties while working due to the mismatching in calculation regarding different structural factor’s spans such as rafter, joist, beam, or header?

How far can a 2×8 span without support?

To determine how far 2×8 will span without support, you have to take account of the other determiners like the species of wood, usage, the load, grade, spacing, and so on. Therefore, also by depending on the single, double, or triple structure, 2×8 will span in general up to twelve feet. 

It is no surprise that 2×8 spans without needing support to a certain degree however, being knowledgeable about the exact 2×8 span range will help you a lot to decide accordingly and to surpass any possible unnecessary confusion. 

Roof rafter: 

The roof rafter span depends a lot on the species of wood, load, grade, and so on. Therefore, the roof rafter span will be within the range of 6 ft. (being the minimum) to 23 ft. 9 in. (being the maximum).

Floor or deck joists: 

The notion that how long a 2×8 can span depends a lot on the load it carries. Floor or deck joists are designed for withstanding a lot of live loads or temporary loads. However, a 2×8 floor or deck joist can span from 7 ft. 2 in. to 16 ft. to 6 in.  

In addition, floor or deck joists are typically used for the living rooms and a single 2×8 may not be sufficient to give the allowable span or necessary support.

Therefore, you may need the doubling and tripling of the 2×8 element to increase the span up to twenty-five percent. 


When it comes to the ceiling joints, their span is regulated by the use and location. If the location is unoccupied but is filled with minimum storage, then the 2×8 span will vary from 10 ft. to 21 ft. 6 in.

In addition, when it comes to the occupied area with no storage then the 2×8 span will be somewhere between 14 ft. to 25 ft. 

When it comes to the header span, it will be determined by whether or not that header is providing assistance or support to the center bearing floor or to the ceiling or roof. 

Accordingly, if the header is giving support to the ceiling and roof, then the header span will be somewhere between 2 ft. 10 in. to 5 ft. 

In addition, when it comes to the header giving support to the center bearing floor, then the header span will be from 3 ft. to 3 ft. 11 in. However, the header span will also be molded by the usage of a double or single header. 


The span of the deck beam will vary a lot depending on single, double, or triple deck beams. Additionally, this 2×8 span will also vary a lot according to the type of wood as well.

However, a general rule of thumb is for the triple beam to span somewhere between 4 ft. to 10 ft. 10 in.

Moreover, when it comes to the double beam, the span will range from 5 ft. to 9 ft. and when it is a single deck beam, the 2×8 span will be from 3 ft. 5 in. to 6 ft. 


While doing house construction works, determining the span of the pergola beam can be tricky and the span will be thus determined by multiplying the depth by 1.5.

In addition, as there are no fixed rules for pergola beam span, it is always better for you to look at the standard rules and regulations that are presented in the manual. 

However, if you need any rule to abide by, then you have to keep in mind that the pergola beam can provide a span of almost twelve feet. 

How far can a double 2×8 span without support? 

The span of a double 2×8 structural component without support will be molded by the width and depth of the joists.

Therefore, for a double joist, the span will be increased by twenty-five percent whether you increase the thickness or not. 

However, the adding of twice the width will accordingly increase the span which will be up to 8 ft. 9 in.  

How far can a triple 2×8 span without support? 

It is no surprise that a 2×8 structural component’s span is based on being used as a single, double, and triple joint. In addition, the triple 2×8 span will also differ according to the floor or deck joists and according to the beam joints. 

Therefore, when it comes to the floor or deck joists, a triple 2×8 will span more than 11 ft. 2 in. and when it comes to the triple-deck beams, the 2×8 span will range from somewhere between 3 ft. 8 in. to 10 ft. 10 in. 

What factors determine span?

Span is a very important determiner that needs to be taken into consideration when you are measuring the span of a 2×8 structural component.

The several factors that may determine the span are the use, location, the different types of wood, grade, spacing, and so on. 

Type of Wood:

The span which means the extent to which a structural component extends without needing any support can be determined by the type or species of the wood and also by the kind of tree in use. 

In addition, the strength, flexibility, support, and durability provided by the different kinds of woods matter a lot while determining the span of 2×8 because there are some woods whose compression abilities are not the same. 

Accordingly, Douglas Fir, Spruce-Pine-Fir, Pine, Redwood are some of the woods that are very strong structural woods that provide the strength and the needed flexing for making a structural component span without support effectively.

However, when it comes to the determination of span without support based on wood structure, Douglas Fir wood can in turn span more elaborately than any other wood in use. 


Another factor that may manipulate or determine the span of a 2×8 structural component is related to the use or the location.

In addition, on the basis of the 2×8 structural component being worked as a beam, ceiling joist, pergola, deck joist, floor joist, rafter, header, the span of the 2×8 will vary a lot.

Therefore, when 2×8 is used as a beam, the span will be at 5 ft. 1 in. Moreover, when it comes to floor joints, the span may extend to 16 ft.

Furthermore, when it comes to the usage of the rafter, the span maybe 13 ft. 5 in. Accordingly, the span of 2×8 will also vary on the basis of the single, double, triple structural component. 


Load is also a crucial factor that may determine the span of the 2×8 structural component. Here, load basically means the amount of the weight that 2×8 can actually carry.

In addition, this will eventually depend on two other things. One is related to the kind of load or weight that is permanent and the other one is related to the live load which is related to furniture, pets, human, and so on. 

Accordingly, on the basis of these temporary and permanent loads, the span of the 2×8 structural component will vary accordingly. 

How much weight can a 2×8 support horizontally? 

A 2×8 structural component can support almost 60 psf weight horizontally however, the weight a 2×8 structural component can carry also can be determined by the temporary and permanent load, and on the duration of the load as well.

In addition, when it comes to the permanent load, the 2×8 can support 20 psf and in the case of the live load, it can support up to 40 psf. 

How far can 2×8 span 12” on center?

How far can 2×8 span 12” on center depends a lot on the usage meaning it depends on whether or not the structural component is being used as the beam, floor joists, or deck joists.

In addition, the span will also vary considering the different load, grade, lumber, spacing, or dimensions. Therefore, the 2×8 will span 12″ on the center by 25 percent. 

Final Thoughts

The span of 2×8 is determined by a lot of factors such as dimensions, location, spacing, type or species of wood, grade, and load. Therefore, there will be no generalized span. So, a beam may span up to 4-9 ft., a rafter may span from 6 ft. 7 in. to 23 ft., and a joist will span 7-16 ft.