PROJECT TITLE Project No; 25

Chimney Stack CORE

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Height of Stacks above Roof Level

The position of the chimney stack plays a major part in the effiency of the flue.

The effiency can also be affected by the close location of trees or buildings. As th wind passage over these can cause’low pressure’ zones which can cause down draft in the flue reducing effiency.

Recent changes in the regulations intriduced a new formula for height of the stacks in relationshp to their position passing through the roof.

To ensure the stability of tall stacks, regulations

state that the height of an unrestrained chimney

should not exceed 4.5 times the dimension, as

shown below.


Construction of Chiomney Stacks

Chimney stack is the term given to the section of the chimney that poasses through space and extends beyond the roof line.

It is the most exposed part of any building so the workmanship must be of the highest standard

The top of the stack should be well protected with oversailing courses with cement flaunching or concrete capping

Provisions must be made where the chimney stack passes through the roof opening with Lead flashing and apron as well as back gutter.


Provision must be made to prevent moisture passing through the brick structure.

A flexible DPC is built into the brickwork at the lowest point of intersection of stack and roof

The position of the DPC within a stack is one area of construction that causes debate with briacklayers. Some will insist that to levels of DPC are reuired.

The local authorities will interpret the requirements for application within their individual areas.