When you are inside a four-walled room, you would never want the support beam to collapse. Although your number of encounters with cracked beams must be pretty low, this problem isn’t uncommon. It can affect the integrity of the structure and pose safety as a real concern.

To fix a cracked support beam, you need to check the extent of the damage. Retrofitting in the form of jacketing and reducing the beam load are two effective methods to prevent the collapse of support beams. If the cracks continue to grow in width, consider rebuilding the support beam.

Knowing the exact cause of why your support beam is cracking will help you develop the best solution. For that, you need to understand a few things regarding the support structure. Keep reading this article to determine the best way to fix the support beam in your home and prevent beams from splitting.

What Causes Beams to Crack

Beams can crack due to various reasons such as environmental issues, pest damage, natural aging, overloading, and failure of other supporting structures below the beam.

Here are a few common reasons why beams crack:

  • The most common cause of wooden support beams cracking is the drying of wood. This happens especially when the timber used is green or not properly dried. But this is not usually harmless and does not affect the structural integrity of the beam.
  • Beams can crack due to rot or pest damage. This can be caused by termites and carpenter ants and is likely to occur if pest control measures are not taken at the time of construction.
  • Heavily loading the beam by storing very heavyweights over the floor can cause beams to crack. This is rare and usually caused when buildings are not used in ways they were designed for.

Most splits or cracks found in wooden posts occur along the grain and are often due to shrinkage as wood dries. These do not usually raise a structural concern.

How to Check if the Crack in the Beam Is Problematic

Here are two methods you can follow to check if the crack in the beam is problematic:

  • Hold a string tightly between the ends of the beam and check if there is appreciable sagging in the beam. A sagging beam could indicate that the beam is falling apart and that it can affect the structural integrity.
  • Fix a masking tape over the crack and see if the tape stays still over time. If the tape is ripped apart, it indicates that the crack is widening and is a cause of concern. This method takes more time than the first one, but if you notice that the cracks are growing in width, take appropriate measures to fix the beam or rebuild it.

In most cases, a cracked support beam can be repaired by following a series of steps in the correct order.

Assess the Cause of Damage

The first step in fixing a cracked support beam is to examine why the beam cracked in the first place. Beams can crack due to age, rot, insect damage, overloading, and post damage. Although some cracks in support beams are harmless, it should concern you if there is a settlement in the structure.

Check if Jack Posts Need to Be Repaired

Each support beam is propped up by multiple jack posts called lally columns that rest on the concrete floor. These are fixed to the floor using screws and a base plate. If these posts are cracked, deflected, or rusted, a post’s replacement will be the first step.

Here is a video that explains what a lally column is:

To replace the lally column, check whether the column is screwed or fixed to the ground.

If it is screwed, here is what you have to do:

  1. Take off the screws from the top and bottom of the column.
  2. Use a jack and fix a temporary post near the existing lally column.
  3. Raise the jack until the temporary column is strongly pressed against the beam and raise the beam a little from the existing position. This will relieve the load from the existing lally column.
  4. Now remove the broken lally column.
  5. If the lally column is fixed to the ground, transfer the load onto a temporary post using the jack.
  6. After ensuring that the load is properly transferred to the temporary post, cut off the existing lally column at the base.

How to Fix the Support Beam’s Crack

Once you ensure that all the jack posts are structurally sound, the support beam’s crack can be fixed. A quick way to repair the beam is to use an angle iron underneath the beam’s cracked part. This is to make the steel take the load even if the beam cracks fully.

Follow these steps to fix the support beam:

  1. Ascertain the required size of the angle iron. Ensure that the width of the bottom flange of the angle iron measures more than half of the support beam width to get a firm grasp of the support beam by the steel angle.
  2. Get an angle iron of sufficient flange length fabricated from any metal shop. Make sure the thickness of the angle is adequate (at least 3/8 of an inch thick). Put holes in the angle iron at intervals for inserting lag screws through it.
  3. Remove any utility lines that run through the support beam. These could be plumbing or electrical lines. Turn off water and power before attempting to remove any utility lines.
  4. Pry open the joist hangers away from the bottom of the support beam for inserting the angle iron using a pry bar. Make sure to move only the joist hangers at the part which needs to be fixed. This will depend on the length of the angle iron as well.
  5. Once the joist is pried away, there should be a nice small gap for fitting in the angle iron on to the support beam. The best way to fit in the angle iron is to jack it up into place. Using the jack and the temporary post, push up the angle iron into the gap between the joist hanger. Also, push up the support beam using the temporary post as a prop to push up the angle iron.
  6. After the angle iron is fit into the gap and is wedged against the support beam, use lag screws of sufficient length to screw the angle iron on to the support beam. After fixing the angle iron, the temporary post and the jack can be removed. Any removed utilities can now be put back on.

How to Prevent Cracking of Beams

Once your fix the cracked support beam, keep in mind the following tips to prevent similar incidents in the future:

  • While constructing, use quality timber that meets your state’s building standard codes. Also, follow the manufacturer’s instructions for storing the timber at the site.
  • Avoid overloading the floor of the house using heavy equipment or machinery.
  • Check for pest damage or rot spreading in the beams through visual inspection, especially in old houses.
  • If there was a fire in the house, carefully check the structural members to ensure no structural damage.
  • All jack posts or lally columns must be intact and rust-free or rot-free. For wood jack posts, check it by driving in small screws at the bottom and assessing if the wood is soft due to rot.

You may also like: Best Products for Repairing Rotten Wood


By now, you might know how to determine what exactly caused your support beams to crack and how you can fix it. Also, follow the tips mentioned in this article to prevent the cracking of beams in the future.

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