In a case of WHEN HOUSES ATTACK ... one of the guys from the show "Sell this House: Extreme" found himself covered in blood after he was smashed in the face by a falling mirror. EXTREEEEEME!!

Here's what happened ... Charlie Frattini -- the construction guy who renovates the homes on the hit A&E reality show -- was taping an episode in Miami, FL last Friday ...  when a very large mirror he was attempting to secure to the wall came crashing down onto his face.

The mirror shattered ... and at least one of the pieces sliced open a 5-inch gash right above of his forehead. With blood literally dripping down his face, Charlie went to a local hospital ... where he was stitched up and released.

After the incident, Charlie -- sporting 2 nasty black eyes -- taped a video statement and joked about the situation ... "I got in a fight with a mirror, and the mirror kicked my ass."