A Conversation with Bryologist Bruce McCune regarding moss on roof tops
This informal interview with Dr. Bruce McCune took place on Tuesday May 20, 2014, while touring 6 roof tops of different ages and moss conditions at this home in Corvallis Oregon. Questions and Responses are summarized here for ease of reading. Written by Morgan Schneider
Potential moss benefits...
This roof was put on 14 years ago, it is south facing and heavily shaded. For this reason the percentage of this roof covered in moss is much higher than other south facing roofs put on at this time.
Notice that the shakes without moss are beginning to cup and pull away from the roof. Small blue arrows point to this on the left side of building
Also note, that the shingle covered in moss are still laying flat and not pulling away from the roof or distorting in any way. Small yellow arrows point to this on the right side of the building.
Dr. McCune believes the moss is offering protection from both temperature and moisture fluctuation.
The most abundant moss on this roof top is Antitrichia californica.
Notice that the shakes without moss are beginning to cup and pull away from the roof. Small blue arrows point to this on the left side of building
Also note, that the shingle covered in moss are still laying flat and not pulling away from the roof or distorting in any way. Small yellow arrows point to this on the right side of the building.
Dr. McCune believes the moss is offering protection from both temperature and moisture fluctuation.
The most abundant moss on this roof top is Antitrichia californica.
Potential fire hazard...
The photo above is from a building in the HG Andrews Experimental Forest, located in the Willamette National Forest. The dense canopy and abundant moss on this roof has caused concern over an increased fire hazard.
Q) The Forest Service has raised some questions regarding fire concern and the accumulation of moss on rooftops. What do you think about this concern?
Dr. McCune: If you live in a place with a fire hazard and are trying to build a fire barrier around your house the dry moss might be a concern. However, most places in town will not face this problem. Also, a large Douglas fir over your home may be more of a hazard than the moss. Another consideration is that if you wet the moss down, you have created a large wet sponge which could offer some protection from fire.
Q) The Forest Service has raised some questions regarding fire concern and the accumulation of moss on rooftops. What do you think about this concern?
Dr. McCune: If you live in a place with a fire hazard and are trying to build a fire barrier around your house the dry moss might be a concern. However, most places in town will not face this problem. Also, a large Douglas fir over your home may be more of a hazard than the moss. Another consideration is that if you wet the moss down, you have created a large wet sponge which could offer some protection from fire.