How do you measure a three-sided, bay, or peninsula fireplace?
You measure the opening on every glass side, plus the depth and height, because these multi-sided units are defined by more than one face. For a three-sided (peninsula) fireplace you record the front width and both side widths; for a bay, you measure the flat front and the two angled returns. Get the framing depth too. When in doubt, we come measure — the numbers have to be exact.
Why one width isn't enough
A standard fireplace has one opening, so one width, one height, and one depth describe it. Multi-sided units don't work that way. A three-sided (peninsula) fireplace has glass on the front and both ends, projecting into the room like a bar; a two-sided (see-through) unit is open front and back through a wall; a bay unit angles its glass forward on the two sides.
Each glass face is a dimension that determines the appliance and the finish. So the measurement isn't a single number — it's the front width, each side width, the overall height of the opening, and the depth from front glass to back, all recorded separately.
Walking through each style
For a peninsula (three-sided), measure the front opening width, then the width of each side glass, then the opening height, then how far the box projects from the wall. For a bay, measure the flat front, then the length of each angled return, then height and depth. For a see-through, you measure the opening in both rooms — they should match — plus the wall thickness the unit passes through, since heat and finish get split between two rooms.
In every case, note whether it's a factory-built (prefab) unit with a metal firebox or masonry, because that changes what fits. We always double-check depth against the framing, since these units project and clearances to combustibles are strict.
This is a measure-in-person job
We're happy to talk you through it, but multi-sided fireplaces are exactly the ones where we'd rather come out and measure ourselves. There's no forgiveness in the numbers — a peninsula or see-through unit has to fit an opening that's finished on multiple faces, and the clearances to nearby walls and any mantel are unforgiving.
A free in-home assessment lets us capture every face, confirm the venting path, and check whether you're replacing a prefab with a matching prefab or reworking the opening. Call (828) 545-0525 and we'll bring the tape measure and get it right the first time.
Related questions
- How are see-through fireplaces measured?
- How do I measure for a corner fireplace?
- How do I measure a fireplace with an arched opening?
- What measurements does a fireplace dealer need before quoting an insert or log set?
- How can I tell if I have a masonry or prefab fireplace when measuring for an insert or logs?
- How many BTUs per square foot do I need to heat a room with a fireplace?
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