Roll roofing installation, inspection, troubleshooting, repairs:
This article describes mineral-granule coated asphalt roll roofing roofing materials, choices, installations, inspection, defects, roofing repairs, and product sources. Our page top photo shows our client pointing to a low slope area on a roof where mineral-granule coated asphalt roll roofing was applied after shingles in that location had leaked repeatedly. This article includes a description of severe wear and early failure of a mineral-granule-surfaced roll roofing installation over an older metal roof.
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Roll roofing is simplest product to install on a small section of low slope roof is 90-pound roll roofing.
This consists of a heavy, asphalt-saturated organic or fiberglass felt with a granular surface. Rolls are 36 inches wide and weigh 90 pounds. Single-coverage roll roofing typically has a 2-inch lap with exposed nails and is used mainly on utility structures.
Double-coverage roll roofing is installed with a full 19-inch lap joint, leaving a 17-inch exposure, with a 2-inch head-lap.
Nails are concealed under the lap joints that are sealed with asphalt lap cement. With two layers of protection, double-coverage roll roofing is acceptable for small roof areas and can be used on roofs as shallow as 1:12.
-- Adapted with permission from Best Practices Guide to Residential Construction.
In its earliest forms roll roofing consisted of sheets of felt canvas or cloth that were impregnated with asphalt, then rolled flat along a low-slope or even some steeper sloped roofs with the material's long edge parallel to the building eaves.
Modern 90-pound asphalt roll roofing is built of mineral-coated fiberglass-reinforced mat or organic-mat (bituminous impregnated paper) material very similar to asphalt roof shingles, in 36-inch wide material sold in 36-foot long rolls. Roll roofing is coated on both sides with asphalt and its upper or exposed side is protected with mineral granules.
Common roll roofing material colors are white, brown, black. You may find some roofers referring to roll roofing as "90-pound felt" since a 36-foot roll of the material, able to cover about 100 sq. ft. (one roofing "square") weighs close to ninety pounds.
Our roll roofing material photo (left) shows that this roll was a bit out of round. When buying roll roofing avoid rolls that are squashed as they may be difficult to roll out smoothly (give the material time to relax and flatten before nailing).
Also avoid rolls whose ends are badly damaged as it may make for uneven or raised seams.
This is an inexpensive roofing material often installed (over 15# felt underlayment) by homeowners and do-it-yourself-ers.
Nonetheless roll roofing installations will have a longer life if installed according to the product manufacturer's instructions, nailed at proper intervals, and with seams properly sealed.
It's also important to install roll roofing over a smooth sound roof deck. If the roof decking sags, ponding on the roof surface after rain may reduce its life.
Overlapping strips of asphalt roll roofing are installed over the roof surfaces with overlapped edge joints sealed, usually with a heated asphalt compound, or cold-applied using a similar sealant that functions at lower temperatures.
Sketch courtesy of Carson Dunlop Associates.
Probably in part because asphalt roll roofing is typically used on low slope and nearly flat roofs, it can have an anticipated wear life of less than ten years, often five years.
The life of roll roofing may be extended by coatings.
As Carson Dunlop Associates' sketch (at left) illustrates,
Not quite so common, but we also see misapplications of roll roofing such as:
Watch out: Because mineral-granule-coated modified bitumen roofing can be mistaken for roll roofing, and vice versa, readers should also see MODIFIED BITUMEN ROOFING. These products look a lot alike but their properties and installation procedures are different from one another.
Here is a good picture of severely degraded mineral surfaced roll roofing. It was mistakenly and unnecessarily placed on top of a metal panel porch roof, the type fabricated with U-shaped overlapping panels. You can see the lines of the vertical legs of the roof panels clearly in the surface of the roll roofing. These do not require a secondary roof membrane.
Also, mineral surfaced roll roofing requires a smooth and flat surface to ensure property bonding and for full support. This roofing sagged over time, allowing water to pond, and in my opinion, greatly shortened the lifespan.
However, based on permit information and my opinion on the condition, it was ten years old, which is at the end of the anticipated lifespan anyway, according to technical resources (like inspectapedia.com ). But the age was unconfirmed.
- 2016/06/10 - Andrew Kester, P.E. 60993 is a forensic and structural engineer practicing in Florida. Also see CELLOPHANE STRIP ENGINEERS' VIEW
Above: a closer look at the rapidly failed roll roofing installation over what looks like an exposed fastener metal roof panel system. [Click to enlarge any image]
From the severity of the cracking and crack pattern, I'd bet that those cracks were gross 3-5 years back. Do you think we actually have two effects: linear cracking in the roofing where it bends over the metal roof joints and significant variegated cracking throughout the roofing material.
Would you agree that since this roof, as photographed and reported to be ten years old, has severe variegated cracking worse than we might expect even on a ten year old roof. In turn that might suggest that the cracks were evident 3-5 years ago, had the roof been inspected at that time?
If I'd seen these cracks on a 5 year old roof I'd have said it was failing faster than normal, perhaps because of a combination of bending at the roof panel seams and heat reflected from the metal roof surface over which it was installed?
I know that an engineer should avoid speculation but still, if you thought the text above were reasonable I'll include it.
As the metal roof below this roll roofing failure is clearly not a standing seam roof, I infer it's almost certainly what we call "barn roofing" or more properly, exposed fastener metal roof panel systems consisting of overlapping panels with raised lap joints rather than standing seams. Those lap joints are usually through-bolted to the structure below; the bolt heads may make additional wear points in any membrane roof later installed over the metal.
Also see METAL ROOF EXPOSED FASTENER SYSTEM
Here is what a typical manufacturer of roll roofing expects to find below an installation of their mineral-granule-surfaced residential roll roofing product:
Install roll roofing directly over clean, dry plywood minimum 15/32” (11.9 mm) decking or approved equal on slopes equal to or greater than 1:12 for the concealed nail method or 2:12 for the exposed nail method. - source: GAF Corporation, "Technical Advisory Bulletin - Options and Application Procedures for Roll Roofing Products", retrieved 2016/06/13, original source: http://www.gaf.com/Residential_Roofing/Residential_Roll_Roofing/Mineral_ Guard/Options_and_Application_Procedures_for_Roll_Roofing_Products_Steep_Slope_Technical_Point_TAB_R_2011_119.pdf
Roof Decks: For use on new or re-roofing work over well-seasoned, supported wood deck, tightly constructed with maximum 6" (152 mm) wide lumber, having adequate nail holding capacity and smooth surface OR minimum 3/8" (10mm) thick APA–Engineered Wood Association labeled exterior grade plywood/OSB decking. Be sure that there is no moisture on the surface of the deck or within the deck (which can have an adverse effect on product performance). Nail tin or other metal over gaps or knot holes larger than 1/4" (6.4mm). Sweep all dirt and debris from roof deck prior to application. - source: GAF Corporation, "Application Instructions for Mineral Guard® Residential Roll Roofing", retrieved 20`6/06/13, original source: http://www.gaf.com/Residential_Roofing / Residential_Roll_Roofing/Mineral_ Guard/Mineral_Guard_Residential_Roll_Roofing_Installation_Instructions.pdf
- Daniel F.
... what you are suggesting is perfectly reasonable. I also thought the infrared rays reflected from the metal roof probably exacerbated the degradation of the roll roofing. Since I was not there to investigate that section of roof, I am comfortable you using that photograph and your commentary is reasonable.
I will keep sharing these types of dramatic photographs that make for good academic discussion. I have to dig up a few photos where you can see the huge difference in degradation on the same roof based on which slope it is on, i.e., south exposed roofs in Florida are always worse than other slopes. I am thinking of this one where they had recently removed large solar panels, and the rest of the roof was in bad shape but those areas covered by the panels looked much newer. UV rays and rain, shingles worst enemies!
Continue reading at ROOF LEAK DIAGNOSIS & REPAIR - home or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.
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Questions & answers or comments about types of roofing materials, installation, inspection, diagnosis, repair, maintenance, & warranties
There are no trees around the house. We live in New Jersey right on the bay. Our builder had the gutters washed, but the black stain could not be removed.
Also, upon further investigation, my husband found extra shingles stored under the eaves of our attic. To our surprise "Royal Roofing" was stamped on the inside of each shingle--not Eternit!
Are these two separate companies? The architect's notes indicated "Eternit" as the roofing tiles--now I'm confused. Unfortunately, he has passed away and his business was dissolved.
When I contacted Eternit in England via e-mail, they said that they never manufactured a roof tile made from "recycled" tires. That was exactly how our architect described the tiles to us! He was very excited about its reported durability and longevity. Once again, Daniel, I hope you can shed light on this dilemma! - M.
I'd like to see sharp photos of your roof shingles in place, both the field of the roof and closeups of the shingles, and I'd certainly want to see photos of the surfaces and markings of the extra shingles you found in your attic so that we can more accurately identify and contact the manufacturer with follow-up questions.
I'm not sure that all of the black stains in your photos are due to the composition of your roof shingles, and it's common to see some black stains on the outer edges of white K-profile aluminum gutters even on asphalt shingle roofs. More about diagnosing building stains is at STAINS on & in BUILDINGS, CAUSES & CURES.
But if your roof shingles are bleeding out significant levels of black debris, in addition to needing to clean the building exterior, you ought to be able to avoid stains on other building surfaces by properly routing roof runoff into gutters and downspouts.
A second question that might arise is whether or not black runout stains from a roofing product are a sign of deterioration or reduced roof life. Certainly the manufacturers of plastic and composite roof shingles we list below all promise rather long-life warranties.
Your roof shingles may be a Canadian product: Royal Dura Shingles. But first let's correctly identify your shingles and then ask the manufacturer for an opinion and advice. "Royal" as a roofing name alone is a bit broad as you'll see from our references below, including manufacturer names, roofing company names, and several asphalt shingle product names including IKO Royal Estate shingle and GAF Royal Sovereign shingles.
"Royal Roofing" may be a company name or a shingle model produced by a company of a different name. In any case, Eternit, a company about which you asked us previously, produced fiber cement shingles and is separate from Royal Group Technologies who produce Dura slate roof shingles (see our company list below).
Several companies produce roofing shingles made from recycled materials, rubber, composites, plastics, including:
We live in a condo building, four story, concrete structure with brick face.
We have had our flat, concrete roof repaired multiple times in the past few years. Last year the roof was sponge-y with water. We had repairs made in all areas as per a building inspector's advice, and a water expert's advice, except for some tuck pointing problems which were terribly expensive, and didn't look all that problematic . Also we installed roof vents.
This summer the roof is no longer sponge-y. It is solid. But the owners of the fourth (top) floor apartment are having interior work done and are discovering black mold and water/moisture coming in in the very areas they want to repair.
The roof LOOKS good, flashing and parapets are tight, caps on parapets are repaired and in good shape, roof surface (modified bitumen) has been sealed this summer and looks to be in good shape.
Is it possible this is still water percolating down from our concrete roof? Or should we be looking for new leaks?
Should we be calling yet another roofer? Or should we be waiting for the interior to be free of the old buildup of water which is still making its way down from the soggy, sponge-y roof we had last summer.
Thank you for any advice you can give us. - M.J.
Our home page for roof leak detection, diagnosis, and repair (where to patch) is at LEAKY ROOF DIAGNOSIS & REPAIR. Excerpts are below.
If your roof is low slope or flat water travels and it can be tricky tracking down a leak - an inspector using infra red and moisture meters should be able to help sort out the question of whether there is an active leak and if so where it originates. As you report that the top floor occupant has found wet areas, it seems likely that other than concrete and structural members, other wet materials such as insulation will need to be removed - a step that will help trace the size and pattern of wet areas back to inspection points on the roof above.
It's common on large commercial buildings and apartments to simply add another layer of roofing over leaky flat or low-slope roofs. Sometimes the roofer will also put down a layer of insulating board first. As long as the roof can be mechanically secured soundly to the structure, that practice is acceptable in many communities.
But roofing over wet layers of old material can lead to future troubles including
If the roofer roofed over wet conditions they could take a long time to dry out, particularly if the roof was installed atop multiple layers of old material. You didn't say how long ago the new roof was installed nor whether or not there was a tear-off of old layers. Also, while we like modified bitumen as a roof covering material, the roof can "look good" but could have improperly made seams.
An experienced roofer or roof inspector will look closely at the modified bitumen seams and flashing details to be more confident that at least from above the roof doesn't show obvious leak points. See our detailed response to this question at LEAKY ROOF DIAGNOSIS & REPAIR. Also see MODIFIED BITUMEN ROOFING for details about the type of roofing installed on this building. .
Questions & answers or comments about roll roofing installation, life, leaks, repairs..
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