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TOPIC: Algae and Mold Questions

Algae and mold on metal roofing surface.

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With background and first-hand knowledge of algae and its effects on asphalt roofing products, is metal roofing also affected by algae staining? Shingle manufacturers, of course are waist deep in "fungus resistant" shingles.The new legal eight ball is mold, most of which is caused by moisture from building leakage in general from what I understand; is metal roofing subject to these claims?
Guest User

5/30/2003
Lets look first at three main levels of finishes available for residential roofing Natural- This contains the exotic metals such as copper, lead, zinc and stainless as well as Aluminum and Galvalume steel. The finish is very smooth and as such provide with resonable slope, the roof will flush all the dirt off and not provide a base for algae to start. Additionally natural products that contain zinc in the metalic coating such as Galvanized and Galvalume actually act as an anti fungacide. Pre-Painted- Same generally holds true here as well especially with the two types of paint finishes recommended for metal roofing; PVDF (Kynar 500/Hyplar 5000) and SMP (Siliconized Modified Polyester), both of wich have a very smooth slippery surface that flushes well. Granular Coated- Generally these products use a screened down version of the standard roofing granule except for Dura-loc. The differance here is that the stone is finer so it flushes better and the acrylic biders contain anti fungasides. Dirt can still build up, but it can generally be washed clean with a low pressure washer with soap and chlorox without leaving a stain. To grow mold one needs moisture heat, limited oxygen and of course spores. An poorly ventilated attic can become a prime host in a house with no interior air barrier allowing moist, warm air to migrate into the attic. You still need the spores to start it though. The best case I investigated was a 4 plex that had fire walls up through the attic each way on centre. While the attice was poorly vented as a result of insulation upgrades plugging the soffit one still needed moisture and spores. This was provided by a tenant who had a horticultural operation in his bathroom and had re routed the bathroom exhaust duct in the soffit back into the attic and cut it into the plumbing stack. This worked fine but be did not fasten the joints and the expansion and contraction with the teperature disconnected it at the stack. I don't know which was more deadly, the plants he was growing in the bathroom or the mold in his quadrant of the attic.
Allan Reid
Dura-Loc Roofing Systems, Inc.

5/30/2003
Guest User

7/29/2003
My house is in Portland, Oregon. At our hilltop locale we get over 60" of annual rain concentrated from October through June. There are many successive days of minimal, if any, drying. Moss forms on my roof, mainly on the north, less sunny side. Each year I do a manual or power wash to clear the surface as best I can. I have been advised to string a copper wire along the roof's peak to generate chemicals to kill the moss. What do you judge to be the most efficient and effective way to prevent moss accumulation and if formed to remove it?
Guest User

7/29/2003
Please advise -- is this a metal roof? And, if so, what type of metal is it, what sort of coating is on it, etc? Todd Miller
Todd Miller
Isaiah Industries, Inc.

7/29/2003
Could you recommend a brochure or book that discusses vertical panel sheet metal roofs. I have such a roof and am interested in learning about maintenance and repair techniques to carrry out myself or discuss with a contractor.
Guest User

7/29/2003
Each manufacturer has their own specifications. You could contact the National Roofing Contractors Association and purchase their generic manual on vertical rib metal roofing. If the roof was put on correctly you should have little maintenance. You should check your roof each spring even with a pair of binoculars to check for limb or ice damage. Check the caulking on flashings every 5 years. If you need to replace use a good Butyl based two part caulking. If you have exposed screws then check every few years to see if any worked loose. Other than that look for loose flashings or building movement. You may want to wash the roof down to clean it once and a while. Use a garden hose sprayer to apply a mixtur of household beach, TSP and Sunlight dish soap. Spray on, let sit a little without drying and then flush off. Hope this helps.
Allan Reid
Dura-Loc Roofing Systems, Inc.

7/29/2003
I erred in saying that moss formed; it is mold. The roof is described by the contractor as sheet metal (a roofing installer today called it galvanized steel) and it has a paint coating whose composition is not known to me now (my wife remembers the contractor saying the coating was applied and baked at the factory.) In a few days I can get more information from the contractor.
Guest User

8/1/2003
Mr. Reid: Thank you for your response. But, what is TSP and what should be the proportions in the mixture?y
Guest User

8/1/2003
Tyoically, equal parts of TSp, bleach, detergent, and water could be used. Be sure to clear waterrinse after using. TSP is trisodium phosphate. One brand name of TSP is Soilax.
Guest User

8/4/2003