What Size Beam Do I Need To Span 14 Ft, 18 Ft, Or 20 Ft? [Inc. How To Build A Beam Step By Step]

One of the most basic structural elements in construction is the beam. If you are building beams for your home, you're probably wondering what size you'll need to span different widths in the areas you are working on. We researched different beam sizes to find the answers for you.

To span 14 feet, you will need three 2x12 or one 6x12 wood beam. For an 18-foot space, you'll need three 2x16 or one 6x16 wood beam. If the width is larger, like 20 feet, you will need four 2x16 or one 8x16 wood beam. These measurements are the minimum sizes typically used in residential projects.

Figuring out the right sizes of beams you'll need can be a little overwhelming because of the different measurements involved. In this post, we will also talk about how you can build a beam step-by-step. We'll also talk about load-bearing beams and ornamental beams, so enjoy reading this post!

Wooden frames of a house with plyboards and other construction equipment's lying around, What Size Beam Do I Need To Span 14 Ft, 18 Ft, Or 20 Ft? [Inc. How To Build A Beam Step By Step]

What Size Beam Do I Need To Span 14 Ft, 18 Ft, Or 20 Ft?

Beams are structural elements that are placed in all homes and buildings. These support structures are typically made from wood, steel, or concrete. Generally speaking, beams carry the load from one load-bearing wall to another.

Without beams, there is nothing that can hold the structure together. Most likely, a structure will immediately bend or break without the support of beams. Columns and slabs need beams to distribute the weight of the load across the entire area. Because of this, you must make certain calculations to know the right size of the beams a house should use.

Wooden framed install for a two story house

During construction, different-sized beams are used to span the areas of the house. Areas that are narrower or wider will need appropriately-sized beams that span these widths. A structural engineer will know how to measure and calculate the load the beams will take and the right size to span different widths.

The beam size you will be using is measured with the depth and width of the wood. Different woods also have different grades, so this will affect the load the beam can handle. In construction, high-dense, close-grained wood is a preference for many homes because of its resistance to insects and rot. 

Here are the sizes of the beams you will need to span the area of your structure:

14 Feet

If you are going to put up a beam that needs to span 14 feet wide, you can use either a three-ply beam measuring 2" x 12". You can also use a single-ply beam measuring 6" x 12". 

18 Feet

For beams that need to span 18 feet wide, you can use a three-ply beam measuring 2" x 16". Alternatively, you can also use a 6" x 16" beam.

20 Feet

Wider spaces, such as those that measure 20 feet need four-ply beams that measure 2" x 16". You can also use a single-ply beam measuring 8" x 16".

For beams that use multi-ply pieces of wood, make sure that they are pressed plumb and tight together. This will ensure they can carry the weight the beam is expected to hold.

Are All Beams Load-Bearing?

Interior of an ultra-luxurious modern kitchen with visible wooden trusses, dark wooden flooring

While beams were originally made to be load-bearing supports for a structure's frame, beams have also changed their purpose throughout the years. Nowadays, some beams are purely decorative in purpose and can be installed without a structural engineer.

These faux beams are not load-bearing. Instead, the load-bearing beams are made during the house's construction and are completely hidden from sight. The faux beams are installed simply for design, and it does not need to be completely solid.

Most faux beams are made using thinner, more affordable 1-inch thick boards. You can mimic the thickness of real load-bearing beams using these boards by gluing three of them together. You can easily lay out the design of these beams, and you can even add beams that go opposite each other.

House undergoing construction showing all the wooden membrane

All it takes is a good layout for the ceiling beams to achieve the look you are aiming for.

Faux beams are also easy to install, and they can be laid out in many different ways. You simply need to attach them to cleats attached to the ceiling. The beams are light enough that they can be screwed onto the cleats using screws.

Step-By-Step Ways On How To Build A Beam

The process of building the load-bearing beams for your house is the job of your structural engineer and contractors. However, this doesn't mean that you cannot build your own decorative beams for the interior of your house.

Wooden framing of a house under going construction

A wood beam ceiling is a great DIY project that you can do on your own over the weekend. It's a great addition to your once plain-looking ceiling and should match any home style. Usually, this style goes well with rustic homes or with traditional decor. However, modern-designed homes also look beautiful with these faux beams in place.

If you are planning to set up and build your own beams, there are some things you have to consider. The width and depth of the beams must be proportional to the size of the room. Keep in mind that the bigger the room and the higher the ceilings, the beams must be wider and deeper.

This video will show you how to install faux beams for your home.

How to Build a Beam


  • measuring tape
  • cleats
  • primed lumber or hardwood (1x6 and 1x8 board)
  • stain or paint
  • electric screwdriver
  • screws
  • stud finder
  • level
  • table saw
  • featherboard
  • reinforced packing tape
  • 18-gauge brad nails
  • screwdriver
  • sanding block
  • wood glue
  • wood putty


  1. Start by creating a layout and measuring the distance of the beams on your ceiling. Use a measuring tape and a pencil to mark these areas on the ceiling.
  2. Fasten the 2x6 cleats to the ceiling joists. To hold them up, use a few boards to wedge them in place while you screw the cleats to the ceiling.
  3. If the ceiling joists are running opposite the beams, use a stud finder to find the studs and drive two screws to attach the cleats. If the ceiling joists are running with the beams, drive a screw every 16 inches into the cleat.
  4. Use a level to check how flat the ceiling is. Note the gap of the level between the ceiling and the level. 
  5. Choose the right board by checking if the board is straight. Avoid boards that bow or curve to the side.
  6. Miter the corners of the board using a table saw and a featherboard. The narrow face of the bevel cuts should be at least 5 1/2 inches wide. Do this on the long edge of the 1x8 and 1x6 boards.
  7. Cut a bevel on the opposite side of the 1x6 boards to match the gap in the ceiling. If the gap is 1/4 inch or more, use a 15-degree bevel. If the gap is less than 1/4 of an inch, a 5-degree bevel will suffice.
  8. Arrange the three boards with the bevel edge down and the miter of the boards touching. Use reinforced packing tape to tape the seams together.
  9. Put some wood glue on the beveled edges and stick the boards together. Hold them up using more reinforced packing tape and don't hesitate to use 18-gauge nails on the boards to keep them in place.
  10. Use a screwdriver to burnish the edges of the beams and to smoothen them together.
  11. Sand the beams as smooth as you can and stain them with any color of your choice.
  12. With a helper, hold the beams up to the 2x6 cleats. Using a pencil, place it against the ceiling and draw a line against the top of the beam. 
  13. Take the beams down and sand the beams up to the pencil marks you just made. This will help your beams stay flat on the cleats and the ceiling.
  14. Lift the beams up to the ceiling and screw them to the cleats
  15. Cover the screw holes with wood putty and some stain to hide them.

Final Thoughts

Wooden frames of a house with plyboards and other construction equipment's lying around

Although originally made to provide support to a house's framework, beams have also changed into other uses. Since many homes are built with concrete or wood beams that are hidden by the ceiling, faux beams have become popular. Change the design of your rooms by putting up these faux beams and watch how it adds character to your space.

Are you looking for ways to maintain your house's beams? We have articles that can help you:

How To Fix And Reinforce A Cracked Support Beam

How To Clean Rough Wood Ceiling Beams [A Complete Guide]

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