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How to Repair Spalling Bricks on Chimney

As much as having a chimney in your home is a great advantage, failing to maintain it might be dangerous. That is why the authority recommends regular chimney inspections and mandate instant repair if the chimney is damaged.

Among the common problems that your chimney may have is spalling bricks, and whenever you notice them, you must repair them immediately. You will learn how to repair spalling bricks on chimney on this guide. But first, what is spalling and what causes it?

What Are Spalling Bricks?

Spalling bricks are bricks whose surfaces have broken, eroded, and peeled off, leaving the brick with no face. The brick may eventually crack. Spalling can easily be observed in a chimney as it occurs on the surface.

It is similar to chipping, but the causes are different. Also, the nature of spalling bricks is different from that of bricks with chipping on their surfaces. So, what causes spalling?

What Causes of Spalling Bricks 

The major cause of spalling bricks in a chimney is when you use mortar of lower quality. When the mortar absorbs excess water and the temperature drops to the freezing point, it will expand, putting pressure on the bricks.

If a brick can no longer withstand the pressure, its face may fracture and pop out. It is not uncommon for molds to grow on mortar and make it sandier. This will increase the water absorption property of the mortar and makes it more prone to spalling.

Other causes of spalling in bricks include the age of the bricks and the structural design. Also, since spalling is caused by the freezing of water absorbed by the mortar, the weather condition can play a significant role.

The drainage system of your chimney can also influence the rate of spalling. If the roof allows too much water on bricks and mortar, there could be frequent spalling. 

Luckily, if you have a few spalling bricks, you can repair them yourself. Here is how to repair spalling bricks on the chimney.

How to Repair a Chimney with Spalling Bricks

To repair spalling bricks, you will need the following materials:

  • Hammer
  • Chisel
  • Mortar mix
  • Bricks
  • Trowel
  • Drill
  • Masonry Bit

You can follow the steps below to repair spalling bricks on your chimney successfully.

Step 1: Identify the Spalling Bricks

Since spalling is readily visible on bricks, it is easy to identify spalling bricks on your chimney. This will guide you to know the quantity of mortar and the number of replacement bricks you will need for the chimney repair work.

The replacement bricks must be of the same size, color, shape, and quality as the ones you are removing. If you cannot get bricks exactly like the old ones, at least let them be similar as much as possible.

Step 2: Remove the Spalling Bricks

Once you have got the replacement bricks ready, then begin to remove the spalling bricks. You can use the chisel and hammer to remove the bricks carefully.

Alternatively, you can first use the masonry bit to drill holes in the bricks before cracking them with the hammer. Then use the chisel to get rid of the brick. However, do not remove more than four bricks at a time without replacing them to avoid the remaining bricks collapsing.

Step 3: Replace the Bricks with New Ones

Replace the spalling bricks with new ones and fix them with mortar. After placing each of the bricks correctly, use a trowel to apply mortar at its base and sides.

However, remember that the use of substandard mortar is the cause of the whole repair process. Therefore, make use of the right mortar.

The Take-Away

Freezing and expansion of water in the mortar can cause the bricks’ surfaces to fracture and peel off. This leads to spalling. However, you can repair spalling bricks on your chimney by removing the bricks with spalling and replacing them with new ones.

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