Fireplace Opening Size

When a home is built with a masonry fireplace there is a huge range of possible sizes.

Fireplace opening size.

Do not confuse a small open fire with the builder s opening small open fires are often built within the builder s opening and excavation will reveal the larger recess. Since almost all fireplaces are different your exact opening size will determine the appropriate flashing or surround to accompany your insert. A builder s opening or original fireplace is at the foot of almost every chimney flue and is of a pre determined size you get what you are given. I checked out your specifications page and was hoping for some advice regarding fireplace size.

The most common case is 1 10 of the fireplace opening area but with a minimum size specified. These are exterior measurements. The opening width of this firebox is 42 3 4 at the face of the unit and the height is 35 1 4. It s important to have a builder who knows how a fireplace works and makes sure the fireplace opening and the flue size are the right match to create excellent venting.

The great room that the fireplace will be built in is 16 feet wide by 25 feet deep 400 sq ft with 10 ceilings. Building codes typically require a minimum flue size expressed in terms of cross sectional area in relation to the area of the fire place opening. The size of fireplace insert you require is related to the size of your existing masonry chimney. I d hoped to have as big a fireplace as possible up to 60 wide.

The flashing or surround will cover the area where the insert meets the edge of the preexisting fireplace and cover any unsightly gaps. To properly size a flue you must use a nomograph. Fireplace flue size specifications relation of fireplace size to flue opening dimensions table of required chimney flue size and flue dimensions for masonry fireplaces. There are five key dimensions to measure the height and width of the opening the height and width of the back wall of the fireplace and the depth of the fireplace.

The bottom of the damper should be a minimum of 8 inches above the top of the fireplace opening. To provide adequate draft and safe venting of combustion products the chimney flue for a fireplace has to be adequate in size or cross sectional area. In general the flue can be 1 10th to 1 12th as large as the opening. This part of the fireplace is called the throat.

How high up should the damper be above the fireplace opening. This is a wonderful flue sizing tool. This article series provides information about masonry fireplaces.