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Replacing the chimney flashing

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Replacing the chimney flashing

Check for evidence inside the home around the chimney breast walls or on the upper floor ceiling below the chimney stack for signs of dampness. Dampness in these locations could mean the flashing is worn and needs attention.

Chimney flashing is quite difficult to repair/replace as it is fitted in four sections. The slanted sides need stepped flashing, while the top needs a back gutter and the bottom requires an apron.

  1. Apron flashing

    The apron lies at the foot of the stack and should be the first section to be replaced. It is made in one piece and secured with lead tacks to the top of the tiles.

  2. Stepped flashing

    The stepped flashing is used on both sides of the stack. The sections are tucked into the mortar horizontally between the brickwork at the base of the stack, where they cover the soakers. Soakers are separate small pieces of lead or zinc that are used to weather between the wall and the roof covering. The size of the soakers will vary according to the type of tile or slate used on the roof.

    If the old flashing sections have been removed, then the tiles on both sides have been removed first to allow access to the stepped flashing. To replace this section, lay it underneath the tiles on the side of the stack but over the front apron. Mark its position against the brickwork and mark on the mortar joints. Fitting new lead stepped flashing will give long-lasting waterproofing as well as the most attractive finish to the roof. Point all flashing with a sealant. Repeat the procedure on the opposite side of the stack.

  3. Gutter flashing

    The final section to be fitted is the gutter flashing at the top end. This is normally one piece that sits over the end of the step flashing.

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