I am replacing a wood burning fireplace with a gas fireplace, but in order to install the new unit into the existing firebox, I will need to raise the header in the wall framing about 18". The wall appears to be a load bearing exterior wall, so I am unsure if a can safely change the framing and move the header (which spans 46")? What do you think?
Jackson ~ York, PA
Jackson, it is difficult for me to give you an answer without actually inspecting the existing firebox in your home's wall. Just to be safe, I always assume that any framed-in header is bearing some load, or else why would the header have been built in the first place?
Of course, an existing header doesn't preclude the framing in your wall from being altered to accommodate your new fireplace, but it does require some careful planning on your part to do so safely. Keep in mind, one obvious indicator that the header above your existing firebox is carrying some load from above is its location, which is within the framing of an exterior wall. Another clue that this might be a load-bearing header is the header itself. For example, a beefed-up header made from two 2x8's on edge would probably indicate a load from above, while a single flat 2x4 (similar to a top plate) might mean that the header was only installed to create the opening for your old fireplace.
The key to your project's success is for you to accurately determine if the load being carried by the existing header is so great that some sort of temporary support is needed while you remove the old header and frame in the new one. Perhaps the best way to accomplish this task is to get some advice from a seasoned home builder or a structural engineer who has thoroughly inspected your fireplace, chimney and wall framing. Although it may take only a few moments for a reliable professional to form an accurate opinion on your specific situation, it would certainly be time and money well spent. Good luck with your project and enjoy your new fireplace!