Q&A /

How to Repair a Chimney

Quick Column Summary:

  • Chimney repair for the ages
  • Protect your chimney with a crown
  • Chimney liners
  • Prevent cracks with wire mesh

DEAR TIM: My chimney is constructed with concrete cake and has a thin stucco coating. I know the top of the chimney is not right and some of the blocks are falling apart. At that place are too tiny hairline cracks all over the chimney that don't seem to be serious. What would you lot do if this were your chimney and yous wanted to make repairs that would last decades? What's the most important matter to tackle at present if I don't have enough money to repair the unabridged chimney? John Fifty., Newton, NJ

DEAR JOHN: Your photo is excellent and allows me to give you some solid advice long distance. I tin clearly see the deteriorating concrete block at the summit of the chimney and know exactly why the damage is happening. The good news is you'll be able to restore this chimney and extend information technology's service life for decades.

Permit's get-go the discussion with an overview of chimneys and why those built past some masons are doomed from the beginning. Information technology's of import to think of a chimney as it's ain house or a construction in and of itself.

Water is very subversive to nearly building products, even strong masonry or solid stone. If you add freezing temperatures to the mix, the damage acquired by water happens much faster. You live where winter temperatures do drib below 32 F, so information technology'southward mission critical for your chimney to shed water.

This chimney has some cosmetic cracking and an inferior crown. It can be repaired properly and will last for decades if done right. Photo Credit: John Loughran

This chimney has some cosmetic cracking and an inferior crown. It can exist repaired properly and volition last for decades if done right. Photograph Credit: John Loughran

Can yous imagine how airheaded it would be to build a business firm and non have a roof on it? Everything inside the house would get ruined in a hurry. Chimneys are no different. They need roofs on superlative of them to continue water from soaking into the inside of the masonry. If you only take and so much money to spend, put a proper roof on the chimney and so salve upwards to practice the other repairs.

The roof of a chimney is called a crown. Chimney crowns can exist made from solid slabs of stone, they can be poured physical in place and they can even be metal. No affair what it's made from, the chimney crown'south sole purpose is to shed water to the outside of the chimney where it tin can drop down to a lower roof or the basis.

Not bad chimney crowns have a slope to them and then the water does not pond on top of the crown. The best crowns have an overhang and a drip kerf cutting into the overhanging border and then all water that falls on top of the crown drips away from the side walls of the chimney.

Most masons don't know how to construct a proper chimney crown and they rarely place a metallic flashing pan under the crown. The metallic flashing pan captures and diverts any water that gets past the crown. You never desire whatever water to get into the core of your chimney. Never forget that.

You or the mason you rent needs to tear apart the top of your chimney and remove whatsoever rotten or broken cake. Once you're down to solid masonry, commencement to rebuild. Be aware the chimney liners may have to be extended a lilliputian college to arrange the new thick crown.

Go along in mind the crown should not touch the dirt flue liners. A half-inch gap needs to be maintained between the crown and the liners and this gap needs to exist caulked with a special urethane caulk meant for masonry command joints. This product will Not exist found at a domicile eye. Y'all notice this special caulk at businesses that sell specialty concrete products to masons.

Be sure the new crown overhangs the sides of the chimney at to the lowest degree 3 inches on all sides. This may seem like a huge overhang, only from the footing it will wait perfect. A quarter-inch wide by half-inch deep drip kerf needs to be located virtually one inch in from the outer border of the crown on the underside of the crown.

If the crown is made from poured concrete, be sure that reinforcing steel is placed in the concrete both directions. This steel volition concur the crown together. Do NOT use manifestly bricklayers mortar for the crown. I must exist concrete or a behemothic slab of rock that has a pre-congenital gradient to information technology.

Once the crown is consummate, I would adhere galvanized wire board to the existing cake and restucco over what y'all take. You lot have a rare opportunity to change the entire look of your chimney at this point past roofing it with artificial stone. If you decide to do this, keep in mind the stone is much thicker than the stucco and you'll have to make sure yous go the proper 3-inch crown overhang past the outer surface of the bogus stone.

Do not allow masons to talk you into adding stucco on top of the existing stucco. The hairline cracks yous run into now volition telegraph through the new stucco and your chimney will look horrible in no fourth dimension.

The wire mesh, when attached with the proper fasteners into the solid physical block, volition prevent the existing cracks from coming through the new stucco.

All of this work should be done, if possible, when the outside temperatures range from twoscore - seventy F. The all-time weather condition to exercise all this work are overcast days with no wind. Sunny, hot and windy weather is the worst atmospheric condition to perform masonry repairs because the water in the mortar, poured concrete and stucco leaves the materials also fast.

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