# What Size Beam To Span 18 Ft?

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Beams are typically fabricated from reinforced concrete, which is generally provided with steel reinforcement.

Alternatively, beams may be fabricated from timber, wooden structures, laminated veneer lumber (LVL), etc.

However, whatever the design and material may be, the beam size has to be perfect for the desired result. In this article, we will find out what size beam to span 18 ft you would need.

## What Size Beam To Span 18 Ft?

To span 18 ft, you’ll need a beam that’s at least 15″ broad and 18″ high. It will be necessary for the reinforcing steel to be capable of withstanding the bending moment, which will be M = (wL^2)/8.

### The possible beam size you need:

Method Used | Size |

LVL or GLULAM | 10″×18″ or 9-10″ |

Lumber/wood beam | 2×12 dimensional and set 16 inches apart from the canter |

Steel beam or RSJ | W12, UB 300×140 or ISMB 300 |

## What affects the beam size?

The beam size is always subject to change based on various factors. The species of timber, the amount of lumber, and the load that it bears are all important considerations.

Upper-level deck occupants like fewer posts, thus bigger frame materials are used for longer spans since fewer posts make a better impression.

The maximum length of a beam is determined by the projected live load. Only 40 PSF, the Point Spread Function, is required for residential decks in accordance with building standards.

The longer the length of the joist, the greater the surface area of the deck, which will get support from the joist. Therefore, the beam will also support the same area.

## Beam size general equation:

As mentioned earlier, the reinforcing steel is capable of withstanding the bending moment, which will be M = (wL^2)/8.

To clarify, the steel stress measurement must follow the equation @σ = Mc/I.

- Here, load per lineal foot is = w.
- Here, the total distance from the steel to the natural axis is = c.
- And, the section’s second area moment = I.

If you get the equation right, you can figure out the beam size easily and without any further risk.

RCC beam size for 18 feet span:

Using the thumb rule as a guide, the size of a reinforced beam for a residential building with two to three stories is approximately 10 inches by 18 inches. The beam’s width is 10 inches, and its depth is 18 inches.

The beam must have a minimum of four 12mm bars at the top and four 16mm bars at the bottom, and it must be made of Fe500 with stirrups T8@6 inches concrete (C/C and M20 grade) with a ratio of clear cover 25mm, one to one and 5 to three (1:1.5:3).

### Steel beam or RSJ size for 18 feet span:

According to the general rule of thumb, the size of a universal beam, or Rolled steel joist (RSJ), or steel beam should be ISMB 300 or UB 300140 or W12 for an 18-foot span. The same rule applies for the w beam, hot rolled section, or UB’s.

This means that the depth of the section of the beam should be 12 inches or 300 millimeters and the width of the beam or the flange or 140 millimeters.

This is the optimal, most appropriate, and standard size RSJ beam or steel beam that one should use for an 18-foot span when the load situation is typical.

Always keep in mind that, all these measurement constructions, buildings, or projects are suitable for residential purposes.

### Wood beam size for an 18-foot span:

According to a common thumb rule, for a span of 18 feet, the size of the wood beam or lumber joist should be 2 by 12. This should find its place 16 inches away from the center. This size fits all construction, buildings, or projects for residential purposes.

Most importantly, here 300 millimeters (12 inches) is the ideal depth of the section of the beam and the ideal beam width is 50 millimeters or 2 inches.

In general, a beam or joist that you place 16 inches apart in the center can easily support a span that is 1.5 times bigger than the beam. So, a span of up to 18 feet is possible with a 2×12 beam.

### Loads on Beams (What You Need to Know):

There are two distinct categories of loads to choose from. It will either be an outside load or an inside load. More simply, it will either be on an exterior wall or within the building.

With clear span trusses, the load that the outside wall faces is equal to exactly half of the load that is supported by each wall.

For instance, a structure with trusses and 24 feet by 24 feet footprint will have a 30-pound snow load on the roof. On the other hand, the ceiling will not have any storage.

So, when compared to a structure that has a wall running down the middle, this will result in an amount of load that is twice as much for the external walls.

This calculator takes into account all that has been mentioned above. All you have to do is check the boxes next to the loads you want to use.

The majority of the internal beams are required to accommodate the weight of the roof. If you have any queries regarding anything else, you should get in touch with either the company that supplied you with the item or an engineer.

### Logic and Reason:

In our experience, notwithstanding what the specifications may state, you should never utilize a beam that is any smaller than a two-ply 2 by 8 inches.

People are taught that these confined spaces, which are often door openings on the interior of the building, are the safest places in a home to be in the event of a crisis and that they should position themselves there whenever possible.

### Bearing:

Any header, joist, or beam must always have a bearing of at least 1-1/2 inches, according to the 2012 IRC rules, International Residential Code (IRC). Anything less than that is not excepted.

So, everything over five feet in height receives at least a double cripple. Accordingly, the beam can need much more bearing room when it’s supporting a longer span.

### Fastening:

You can use either the bolts or nails to connect the beams with multiple layers.

A minimum of a 32-inch on-center staggered design with a minimum of a 3-inch-by120-inch nail is essential as the IRC code wants it.

Through trial and error, we discovered that it is best to drive at least one 3 1/4-inch groove shank nail with a.131-inch diameter into the laminate in columns of four spaced one foot apart.

Usually, you don’t have to use bolts. Bolts are only necessary if the material has such severe defects as a faulty “cup” that nails are unable to fix.

## FAQs about what size beam to span 18 ft:

### What are the methods for determining beam size?

There are two methods, e.g., the S 456:2000 method and the thumb rule method.

### Can a 2×12 span 16 feet?

Yes, it can easily span 16 feet. In fact, according to some estimations, it has gone up to 22 or 23 feet.

### Is LVL beam good to span 18 ft?

Yes, it is good as any other beam. You will need 9-10″ GLULAM or LVL here.

## Final Words:

So, the process of figuring out what size beam to span 18 ft is fairly easy. You just need to apply the proper equation and proper knowledge of beam loads.

If you need further assistance, feel free to leave a comment.