Masonry chimney repairs should be done in the spring

By Marge Padgitt

Badly spalling bricks on a chimney

If there are pieces of bricks or stones lying around the yard or driveway, it could be a sign that masonry repair is needed. The first place to look for damages by cold, freezing rain, and wind is the chimney since it is the area most exposed to the elements.

Signs that repairs or rebuilding is needed are missing or deteriorating mortar joints, cracked bricks or stones, or faces of masonry popped off. This is due to the penetration of water into the masonry- and when water freezes it expands, which usually results in the face of a brick or stone breaking off.

Badly spalling bricks

Unfortunately, many chimneys are built with soft type bricks rather than hard type bricks due to the cost.  Soft bricks absorb moisture more easily than hard bricks. After a few years, the soft bricks will begin to show damage, but after 30 years any type of brick or stone chimney will likely show damages of some type, if only to the mortar joints.  In some cases, masons have found completely deteriorated bricks with hard mortar left behind. In other cases, the bricks are good but the mortar is severely deteriorated or missing altogether. When this occurs it is a sign that the wrong type of mortar was used.  For this reason, the Midwest Chimney Safety Council recommends that chimneys should be built or reconstructed using hard bricks and the right type of mortar which will last many years longer than those built with soft masonry units.

Mortar deteriorated so badly that
the chimney is falling apart

Mortar sets up better when the work is done in the spring when temperatures are moderate so the curing process can complete without issue. If the temperature is too cold, the mortar can crack and take a long time to cure. If the temperature is too hot the water in the mortar may migrate to surrounding masonry and shrink. Professional masons can control some of this by adding an accelerant in cold weather or soaking bricks in water before using them in hot weather, but they much prefer working with masonry in ideal weather conditions.

Cement cap with drip edge

The cement cap (crown) should be inspected in the spring to assure that it is in good condition with no cracks, deterioration, or lifting. The cap serves as a roof for the chimney and keeps the elements out of the interior chimney chase where rain can cause damage to the interior flue, smoke chamber, damper, and firebox. Any small cracks or gaps should be filled with high temp silicone, but if large cracks, severe deterioration, or missing sections of the cap exist a new cap should be constructed.  As of 2012, the International Residential Code required a poured formed crown with a drip edge to better protect the chimney from damaging rainwater. The old-style crowns with a slope but without a drip edge actually contribute to the fast deterioration of masonry at the top part of the chimney, so this newer style is a big improvement.

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Marge Padgitt is the CEO of HearthMasters, Inc. and HearthMasters Education in Kansas City, Missouri. Contact her at hearthmastersboss@gmail.com. 

Lighting Damaged Chimneys in Storm August 28

Some of the lightning strikes throughout the greater Kansas City area last night hit chimneys. 

A lightning strike caused major
damage to this chimney exterior
and interior

Pieces of bricks on the ground and roof, or blown out sections of a chimney are signs that a recent event occurred and the chimney may have been hit by lightning.

In some cases the damage is so severe that the chimney must be torn down and rebuilt. In other cases where there are only a few damaged bricks or stones these can be removed and replaced with new bricks.

When lightning strikes a chimney the evidence is usually obvious. There is always an entrance and exit point. The entrance point, usually found near the top of the structure, will likely be a large hole with burn marks, and may include large cracks through the masonry or blown out sections of stones or bricks. The exit point is usually found somewhere within the chimney structure in the flue, smoke chamber, firebox, or even the outer hearth inside the house. 

Damage not so visible from the ground -
lightning hit the top of the chimney and
pushed a brick out on the back side

A professional chimney inspector should examine any chimney that has been damaged by lighting. The chimney sweep should perform a Level II internal chimney inspection with a chimney camera system in order to see if any interior damages have occurred which make the fireplace, furnace, or water heater flue unusable. Only persons trained specifically on chimneys can identify chimney damages properly and provide the needed documentation for an insurance claim.  Lighting and chimney fire damage to chimneys is covered by homeowner's insurance.

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Marge Padgitt is the president and CEO ofHearthMasters, Inc. dba Padgitt Chimney & Fireplace. She is a CSIA Certified Chimney Sweep and NFI Certified Wood- burning Specialist. Contact Marge at hearthmastersboss@gmail.com.