Brand new fireplaces are a dramatic and captivating addition to any living room, dining room, or outside space. For interior purposes where you are cutting into pre-existing walls, or looking to build into a new structure as it goes up, you must be sure to measure for all aspects of your fireplace properly. You have to take into account the surrounding, trim panels, wood fireplace inserts, proximate to the floor and other areas, and you must have proper clearance all the way around it.
Most fireplaces are built into a build out. This is a section of wall set out from the rest of the wall, usually around six to eight inches in depth. It will typically have twelve to sixteen inches clearance on either side of the fireplace. The build up may or may not go all the way to the ceiling. For appearance sake I prefer those that go to the ceiling to give a nice highlight for the fireplace, unless you have an elaborate mantle setup in mind. This build out will allow for the extra space a fireplace will take up in a wall due to its depth. If your wall is being built thick enough that it can be flush with the wall you will not need to measure for a build out.
Now you need to determine the fireplaces actual opening. This measurement refers to the exact area that you will leave exposed, or visible to the room, once the surrounding and trim panels are installed. You get this by measuring the width of the firebox opening, and the height of the firebox opening. With this measurement as a template you can then move forward with positioning your new fireplace.
I would recommend a cut out template that is the size of your proposed fireplace opening. You can then move this about to determine the next measurement, the distance between the firebox and the floor. This crucial step can have a number of factors to consider. I you are building with brick you may simply choose to have the opening a certain number of bricks, usually 2 or 3, above the floor. If you have other design features you may not wish to cut them off mid way, so you can raise or lower it around those. Perhaps you do not want to worry about any of those and would rather work towards having it positioned pleasantly between the floor and the mantle you are going to build.
The next step is to measure for the distance on either side of the firebox. These measurements are known as the distance to the edge, or the distance to the near obstruction. You need this measurement for either side. If you are building into a built out wall area you will want these two measurements to be exactly the same to achieve a centered firebox.
If you have not already considered the height of your mantle, now is the time. Other considerations would be how your fireplace service area will factor in, this is usually an opening on the side for gas fireplaces. Real wood fireplaces do not usually require this feature.