Expert: Bruce E. Johnson - 9/11/2010

Question
QUESTION: I own a home which is the old cinder block with stucco over & only mesh screen & plaster inside.  The roof which is over the sun room, abutting what is structurally an exterior wall, needs repair.  How does one flash or have the joining of the roof to the structure to shed water?  Is there a specific product? Can a tar or caulk be applied?

ANSWER: Hi Diane, you can use various types of metal flashing or fiberglass rolled roofing over the area you need to patch.  Use a good roof mastic and put a good layer of that down first and then stick the patch over that, be sure to have a good layer of mastic along the edges that you nail so that when you nail the flashing down it squishes into the mastic and helps seal the edge.  Then, using a trowel coat the edges and any nails with a good coat of mastic to seal the top of the patch.  I like to use the roofing mastic with fiberglass strands already in it.  These strands help keep the mastic from crascking or pulling apart. You can get the mastic and flashing or roofing materials at a locat building supply store such as Home Depot, Lowes, or other lumber yard..I hope this information helps please feel free to write again regarding this or other matters, sincerely bruce e johnson..bejohnsonconsulting.com

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QUESTION: Just to be clear, the failed roof edge is NOT along the abutting roof and home.  There currently does not seem to be any flashing against the building siding.  IF I were to replace the entire roof, my research shows that a 'Z' metal flashing is the suggested item, but then (assumption) portions of the stucco would need to be cut away to make way for a 4.5" flashing.  Did I get that right?
My assumption with your answer is that it addresses repair to a portion of the roof. Is your suggested technique appropriate for repairing near the exterior edge, by a gutter?

Answer
Hi again Diane, your previous question was a little vague as to where the roof problem was.  You said it needed to shed water so I assumed it was on top of the roof.  Z metal is used where two differing elevations are joined together so I guess this is your situation?  If so then depending on what the sunroom roof is made of and how far below the house roof the sunroom roof is located.  But yes a similar technique would be used as I mentioned in my previous letter.  Only this time the Z-metal would slip under the roofing of the house edge, drop down to the sunroom roof (which is lower?) and then where the bottom flange of the Z-metal lies on the sunroom roof you would put down a coat of mastic, nail the Z-metal and top coat with more mastic.  If your sunroom roof is corrugated fiberglass or metal then you would need to do things a bit differently.  I'm not sure where the stucco comes in unless the sunroom roof abuts the stucco?  If this is the case then an "L" flashing would be used.  The upright flange of the L would be attached to the stucco using the method above, a coat of mastic on the wall, tapcon or stub nail the flashing to the wall, topcoat with more mastic and then do the same to the roof of the sunroom.  Z-metal can be used in this instance also but you are right you would probably need to saw cut the stucco deep enough to inset the small flange of the z-metal into the stucco.  If this is the case then you would probably use "Black Jack" or a similar roof mastic that comes in a caulking tube, fill the saw cut with the mastic and then press the edge of the z-metal into the saw cut and over the roof of the sunroom do the procedure mentioned in my previous email.  I am attaching a couple of simple drawings to illustrate both methods. I hope this information helps please feel free to write again regarding this or other matters, sincerely bruce e johnson..bejohnsonconsulting.com