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How to Restore a Historic Fireplace

Ask This Old House mason Mark McCullough delicately restores a damaged historic fireplace that is built with custom, nearly irreplaceable bricks

Steps:

  1. Start by adding support to the arch of the fireplace with a piece of Masonite and a few pieces of 2x4”, cut to size. Hammer them into place until the Masonite feels fully supported.
  2. Identify the bricks that have fallen out of place or settled and plan to remove only the ones that need readjustment.
  3. Carefully remove the old mortar holding the bricks. High quality, older masonry jobs used significantly thinner joints, so if a chisel doesn’t fit, try a margin trowel or a flat jointer.
  4. Using the back of the trowel, gently tap the brick to see if it will break the bond of the other bed joint surrounding the brick. Slide the trowel through that joint and remove the mortar there as well.
  5. With all the mortar removed around the brick, carefully pull that brick out of the fireplace.
  6. Repeat this process with all the bricks that have settled.
  7. Mix a new batch of mortar to match the old stuff. For thinner joints, a custom mix with a thin aggregate may need to be used. The proportion should be one scoop of mortar to three scoops of sand. Add dye to the mix to match the original color. Add water until the mortar is roughly an oatmeal consistency.
  8. Back and side butter the bricks with the mortar and slide them back into place.
  9. Once the bricks are in the correct position, fill in the joints the way you normally would when repointing.
  10. If the joints don’t match well enough, consider removing all the mortar and repointing the entire fireplace.

Resources:
For a job as complicated like this, only a select handful of masons might be willing to tackle it. Be prepared to get turned down by a few before you find someone who is willing to do the job.

To hold the arch in place while Mark extracted select bricks, Mark used a piece of masonite and scrap 2x4”s, which can be found at any home center.

To extract the brick from the ultra-thin masonry joints, Mark used a margin trowel and a tuck pointer to try and slip between the two bricks. These can also be found at any home center on masonry supply store.

When Mark repointed the brick, he needed to use a special mix to match the original fireplace and also ensure that the aggregate was thin enough to slide through the small joints. To do so, he used a premixed Evolution N mortar with just Portland cement and lime in it, which is manufactured by Ciment Quebec. For the aggregate, he mixed in a Number 70 Silica Sand, which is a thin restoration sand manufactured by Taggart Sand of Pawtucket, Rhode Island. To match the color of the original mortar, he also added a Series H Concentrated Mortar Color, which is manufactured by Solomon Colors, Inc..


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