CHIMNEY RESTORATION REPAIR
Stone chimney restoration begins with a inspection to see how sound the chimney itself is. Mainly the condition of the mortar or (Portland Cement). If chimney is sound but showing signs of deterioration, the mortar joints should be restored. Usually the chimney top is more susceptible to elements. The chimney crown, also referred to as the chimney wash, is the top of a masonry chimney. It covers and seals the top of the chimney around the flue liners to the chimney edge. Most masonry chimneys are built with an improperly installed (wash or crown) constructed from common mortar mix, the same mixture used to lay the bricks of the chimney. This mortar is not designed for and will not withstand years of weather abuse without cracking or deteriorating allowing water to penetrate the chimney. Water damage to masonry chimneys is usually a slow process. the water starts working its way down from cracked chimney crown, wash or deteriorating motar joints to the inside of chimney core and behind stone or brick veneer getting behind improperly installed counter flashing at roof line.This is usually installed by the mason. Also improperly installed base flashing at roof line installed by the roofer.The water then enters the house, water stains will be noticed at ceiling and corners lines of stone or brick inside veneers. Masonry materials deteriorate quickly when exposed to the freeze/thaw process in which moisture that has penetrated the materials periodically freezes and expands, causing cracking. In fact, mortar crowns crack almost immediately after installation because mortar is wrong type and is spread to thin , causing shrinkage and usually tapered to the stones or bricks edge forming only a small amount of mortar at edge and only 1" rise for water runoff from the liner.
CHIMNEY CROWN CONSTRUCTION
A stone or brick chimney crown made and formed out of concrete should be formed at least 3” thick at outer edge and have a 2" inch to 21/2” inch overhang , overhanging stone or brick veneer at outer edge. The top center surface of the chimney crown at the flue liners wall edge and around the flue liner should slope away from the flue liner wall towards the crowns outer edges at a 3/12 pitch 3” rise for every 12” of vertical length of crowns surface width. A drip edge should be formed in the concrete crowns wood framing at outside bottom inside edge. There should be a 3/8" gap between the chimney crown and flue liner, filled with a flexible sealant such as lexel which allows for liner expansion. Without that gap and during the cold season, exhaust gasses warm-up the liner which expands, pushing against the much colder chimney crown, and causes it to crack. Flue liners should extend at leased 2" or more above the crown and altering the height of adjacent flues, making each about 4" higher than the adjacent flue
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