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Chimney Repair

Most chimneys develop serious problems due to cracks that usually occur when mortar joints between the bricks or stones break, wash out, or rip off after a prolonged exposure to the vagaries of nature.

How are the cracks caused in the chimneys?

The most common cause of cracks in the chimneys is the shrinkage and expansion—freeze-thaw that takes place during the freezing winters.

Some minute cracks may also occur during the construction of the chimney itself. It may take quite a few months for the mortar to reach its optimum strength. During this period, cracks may occur due to the strong winds.

Sometimes the plants growing upon the chimney may also result in cracks. This happens when their roots enter into the mortar and rip it away.

As the cracks occur, they allow the moisture in the air to enter the structure. It not only damages the chimney but also the metallic objects such as lightning rod or the satellite dish attached to it.

The cracks in the chimney also admit toxic gases such as carbon monoxide, which can cause a serious health hazard to you and your family.

Tools and material needed for chimney repair

  • Chimney brush
  • A sturdy stool to stand upon while repairing the chimney
  • Mortar raking tool
  • Masonry chisel and hammer
  • Mortar hawk or a pointing trowel
  • Caulk or any other concrete bonding material
  • Weather resistant mortar


Steps before starting the chimney repair

It is always a good idea to read a good chimney repair manual carefully before starting the repair.

Your chimney may have deposits of debris, nests, or creosote, the tar like substance produced by the burning wood.

Before you start the chimney repair, be sure to seal the fireplace so that the debris does not fall upon it and create a mess.

You need to clear these deposits with chimney brush. For that, stand on the stool, insert the brush into the chimney and move it up and down with sufficient force so that you can scrape off the soot without causing any damage to its structure.

If there are plants on the chimney, cut them off at the roots and then remove the dead plant with a putty knife. Also put some herbicide to kill the plants completely before chopping them off the chimney.

Repairing the stone chimney cracks

Clean the area where cracks appear and fill the cracks with caulk or any other concrete bonding material.

The standard procedure for chimney repair is to smooth the bonding material with a putty knife.

If you find that the repaired area is uneven after drying, you can smooth it out using a sand paper.

Quite often the mortar around the stone starts crumbling. You should remove it using a hammer and a chisel. Pull out the mortal portions in squares. Try to dig in approximately half-an-inch deep.

Clean the area so that it is moist but not wet. It is now ready for filling mortar  in it.

Mix the mortar in such a way that it becomes smooth and consistent.  Spread it into the moist excavated area with a mortar hawk or a pointing trowel.

Start applying mortar first on vertical joints and them on horizontal joints.

Allow it dry to a level of consistency where you can leave a mark if you press it with a thumb.

Take care to remove the excess mortar as you carry on with your work.

Keep the mortar moist for about 3 or 4 days to enable it set properly.

Repairing the brick chimney cracks

If your chimney is made of bricks, it would be better to apply clear silane-siloxane water repellent to the bricks. Silane-siloxane enables the water vapors to escape, but prevents the liquid from getting into the bricks.

 The next step is to do the repair with mortar as explained in stone chimney repair.





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