Universal Adjustable Roof Brace (8" - 10" O.D.) AshT Plus Security / Oliver Macleod

Designed to stabilize a chimney extending from 5' to 9' beyond the roof,
or when a chimney is exposed to high winds, this part is supplied with tightening collar and adjustable legs.

Sizing Fireplace Chimneys

The chimney-sizing chart on this page determines the correct chimney size for an open fireplace. For factory-built fireplaces and wood-buming stoves, use the size specified by the appliance manufacturer. In most cases, this is the diameter of the flue collar.

If you need help with a more complicated shape such as a multisided fireplace or an open fire pit please feel free to contact us by phone, fax or e-mail. Our engineering department will be pleased to assist you with sizing, material specifications, and any other technical information you require.

Example: A fireplace with a 24 inch wide by 18 inch high opening requires a 8 inch diameter chimney for 15’ of chimney height.

Chimney Height Design Considerations

Recommended Flue Height

Once the correct chimney size has been determined, there are two factors which can be compensated for when calculating the optimum height of the system-elevation and chimney layout. The higher the elevation, the greater the chimney height required to provide the same draft as an installation at sea level. The more complex the chimney layout is (the more tees, elbows, etc. in the system), the greater the chimney height required to provide the same draft as a straight up system.

The minimum overall height of any chimney system is 12 feet for a vertical chimney with no offsets at sea level. You must increase the vertical height of the system to compensate for horizontal runs, tees, and elbows. To compensate for:

One Tee Add 3 feet. to the minimum height.

One 45° Elbow Add I feet. to the minimum height.

One 90° Elbow Add 2 feet. to the minimum height.

Each foot of horizontal run Add 2 feet. to the minimum height.

Each 1000 feet. above sea level Add 4% to the minimum height.

Example 1: House Built at Sea Level

A wood burning stove is installed on the main floor of a single story house at sea level. The chimney is installed with a 90° elbow through the wall into a tee, then straight up through the roof. To determine the minimum overall height add:

The minimum overall height = 12 feet

1 1/2 feet of horizontal run = 3 feet

One “Tee” = 3 feet

One 90’ Elbow = 2 feet

Additional Height = 8 feet

The minimum overall chimney height required is 12 ft. + 8 ft. = 20 ft.

Example 2: Identical House Built at 8,000 feet

To determine the minimum overall height, add 32% (4% per 1000 feet) to the height calculated in the above example:

20 feet + 32% = 26.4 feet

If the house were built at an altitude of 5000 feet, the overall height would be:

20 feet + 20% (4% per 1000 feet.) = 24 feet

Minimum Recommend