Project Info

Restoration of a chimney in the historic district of Salem, MA.

The two original chimneys of this private home in the McIntire Historic District of Salem, MA. were originally built with soft fired brick and lime putty mortar. Soon after the recent repairs performed with Portland cement the chimneys started leaking water into the house ceilings and walls. From a distance the chimneys do not look all too bad however a closer look reveals a different picture. Portland cement has a much higher compressive strength then the original brick and lime mortar causing brick to crack. Portland cement is virtually waterproof, which does not allow water to escape or evaporate through the joints. The harmful salts contained in Portland cement cause damage by recrystallizing inside the adjacent soft brick. Spalling, cracking and disintegrating bricks are the result of irreversible damage caused by repairs conducted with improper selection of restoration mortars. Once the entire chimney has been prepared, cleaned and treated with limewater the application of the new mortar begins. The lime mortar is prepared by matching it "Like for like" with the original. Samples of the original mortar have been analyzed. This mortar was composed of lime putty and locally sourced coarse sand. The new mortar was prepared by mixing coarse sand of similar color screened to the same size as the original and traditionally produced pure lime putty. The proper mixing procedure requires blending the ingredients without additional water by chopping with a hoe and beating the mix with a large wooden pestle to achieve a stiff but plastic consistency. The mortar is packed into the joints in lifts and compressed with the jointing tool. It is left slightly recessed to keep the face of the brick fully exposed.

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Click images below to make larger.
Historic brick chimney before restoration
Brick chimney repaired with Portland cement
Brick damaged by portland cement and roof tar
Soft fired original brick damaged by Portland cement
Portland cement removed to 1" depth or more
Pointing brick with lime putty mortar
brick repointed with lime putty mortar
brick chimney protected with burlap and watered regularly
restoration completed

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