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All posts in Flat Roof Repair

Sumner Roofing repairs flat roofs.


Slipping: Delaminating / Sliding

This Torch Down Modified roof membrane is delaminating and sliding. This is caused by improper fastening. On roofs with a slight pitch it’s required to fasten each row. Without lifting up every row and breaking the sealing asphalt seams, it’s impossible to tell if the problem is consistent throughout the entire roof or just the areas visible. Generally, if the same crew or person installed the roof, the problem is consistent. There’s a good possibility this roof will continue to experience this problem in the future, especially after high wind events.

Torn/Cracked/Broken Surface

As a flat roof system expands and contracts due to weather the roof system moves. During movement the membrane binds against each other. Sometimes a tree branch or flying debris may impact the roof causing damage. 3rd party damage is another issue. As people walk across the roof they can cause damage. The membrane on this roof has been damaged. Since this leaves the underlayment showing, it is our recommendation these areas are repaired.

Shingle Offset Not Correct

The way membrane roofs work is by their overlapping design. As the previous layer is covered by the next it creates stair step water shed design, disallowing seepage and water backslaps. This stair step design also has a vertical component to it. If each row is not offset correctly, water may enter the system through “T” joints. It is standard practice to stagger each row of membrane.

Ponding Water

A code violation and warranty exclusion on all asphalt based roof systems, ponding water is when water sits on a roof for more than 48 hours without being evaporated or running off naturally. Water ponding breaks down asphalt, which is an oil-based product. Think of potholes in the road. Or, imagine a pot of boiling water when cooking. If oil were added, it would stay on top of the water. On a roof the opposite effect happens. The oil is trapped at the bottom and due to it’s natural properties, tried to rise to the top causing oil migration. Oil migration when the oil and waterproofing properties of a roofing product are pulled out, causing the roof system to break down.

Improper Number of Fasteners

Modified membranes are designed to be installed over an approved surfacing fastened to specific guidelines. If modified membranes are installed over a surface without the proper fastening the manufacturer’s warranty is voided and the roof assembly is out of code. This also leaves the roof susceptible to roof blow-off in the event of strong winds.  In 1994, when a new code system was introduced, the requirements became much more strict. However, most of the good roofing contractors go above code and install more fasteners than required due to lessons learned after the storms.

Improper Fastener Installation

It is important that all fasteners are installed perpendicular to the roof’s surface and driven in at a perfect 90-degree angle. On a Smyrna roof I found areas where the fasteners were not driven straight in and the fastener heads are lifted slightly. Over time this can and will damage the roof system and allow seepage.

Fasteners Uplifting

“High nails” were found on this Immokalee roof. During roof underlayment installation it’s easy for installers to forget about proper pressure setting on their nail guns. In most cases too many nailers are hooked up to a low volume compressor and the air supply is not sufficient to drive each fastener fully. At time of installation only the severe “high nails” are noticeable. When the modified membrane seals to itself a tight bond is formed. “High nails” begin to protrude through the top surface of membrane causing rust and seepage.

No Starter Strip

Membrane Starter strip is a narrow strip of membrane at the perimeter designed to seal perimeter flashings and prevent wind uplift. When membrane starter strip is omitted or not installed correctly strong winds have an opportunity to lift the first row of membrane and cause the “domino effect”. This has led to entire roofs being blown of during hurricanes. The starter strip on this Carthage roof was not installed correctly. Proper sealant was not installed. As a temporary measure the first row can be lifted and sealed. When it comes time to replace the roof make sure your contractor uses specially designed starter-strip membrane to keep your roof’s guarantee and prevent system blow-off.

Flat Tie-In not Sealed Properly

The junction between your pitch roof and the flat roof is called the “tie-in”. This area is specifically important because there are two different roofing materials joining. This Lafayette roof shows evidence that the tie-in area is not sealed properly. It is also very important that the two roof systems have the correct flashing detail and extra sealant protection.

Backwater Laps

When installing a flat roof system it is important to always start at the lowest point and proceed upward toward the roof’s peak. This ensures that each layer of materials overlaps the previous. Even on flat roofs, this principle is important. As water travels, on a pitch or on a flat roof, if two seams are lapped in backwards a backwater lap occurs. This can “cup” water and force in under the layers, causing leaks.

Flashing Rust

Steel metal flashings exposed to the elements can rust over time. Today’s flashings are made of galvanized metal, a process that protects the steel core from rusting. Rust cannot be simply sealed over, as it will continue to grow as seen on this Fairview roof. The rust needs to be cut out and a new flashing installed, then sealed properly. Since the rust is open to the surface and flashings are vital to the integrity of your roof system. We suggest repairing the rusted flashing areas before seepage causes structural damage.

No Sealant at Flashings

Although flashings bridge transitions in the roof, when not sealed properly they are ineffective. Flashing is designed to turn corners and breaks in a roof, which tend to have more movement than other areas. If not sealed properly, these flashings do little to stop water from entering the roof system. This is allowing water to enter the flashing detail area. This can be repaired with minimal expense.

New Flashing Needed

Steel metal flashings exposed to the elements can rust over time. Today’s flashings are made of galvanized metal, a process that protects the steel core from rusting. An example of rusted flashings was found on this Lebanon roof. Rust cannot be simply sealed over, as it will continue to grow. The rust needs to be cut out and a new flashing installed, then sealed properly. Since the rust is open to the surface and flashings are vital to the integrity of your roof system, we suggest repairing the rusted flashing areas before seepage causes structural damage.

Boot Lapped/Sealed Correctly

As with all rooftop objects it is important that proper water flow and installation are considered. Flashing that is not layered correctly and sealant applied in the right junction areas allow water seepage. The boot flange was not installed correctly with the proper overlap procedure. Sealant has done a good job covering up the installation error, but is now showing signs of deterioration. Adding sealant may prevent seepage temporarily but is not a roof cycle solution. The boot should be replaced and installed correctly.

Vent not Lapped/Sealed Correctly

Valley metal is installed by crimping the valley center, fastening the entire length of both edges and then applying mastic to cover the valley metal edge and fasteners. When valley metal is not properly pressed, fastened and/or sealed it causes buckling and waving. Since a valley is designed to channel water between two pitch areas a valley receives more water flow than any other part of the roof. Valley metal buckling disrupts the immediate flow of water and creates water vortices, a circular flow of water that leads to roof seepage.

Plastic Boots Used

As you know, plastic typically dries out rather quickly in our environment. The sun’s UV rays cause oil migration much the same as it does to exposed asphalt. On this Donelson roof a plastic stack flashing was used to seal the pipe. A gap between the pipe and surrounding flashing is visible and allowing seepage. This boot should be removed and replaced with a new lead boot.

Ell Flashing not Sealed Properly

Ell flashing bridges the transition from the roof’s surface and a wall or upright surface such as a curb. On this Walnut Grove roof the ell flashing has not been sealed properly and the shingles are pealing back from the flashing allowing seepage. This can be correctly by removing the area and installing mastic sealant correctly. New membrane may need to be installed in this area. Also, if the ell flashing cannot be cleaned or has too many old fastener holes in it, the entire flashings detail area may need to be replaced.

No Ell Flashing Installed

Whenever a roof surface meets a vertical surface ell flashing is needed to bridge the transition and protect from seepage. Although sealant may have helped avoid leaks, over time sealant breaks down. The correct technique is to install ell flashing here.

Ell Flashing Uplifting

Ell flashing should be nailed every six inches on center. Not enough fasteners were used and the sealant has deteriorated. I suggest sealing the underside of the ell flashing and installing the correct number of fasteners as specified by code. On this Talbot’s Corner roof another layer of membrane should be installed to cover the ell-flashing flange and provide a more aesthetically pleasing transition area.

Ell Flashing Behind Wall Surface

Ell flashing for flat roofs are designed to bridge the roof to wall transition and allow for protection against water intrusion. Water which runs down the roof and wall is caught by the ell flashing and channeled to the roof’s edge. It is important that the ell flashing’s end be flared so it sticks out past the siding/stucco. On this roof the installers did not flare the flange end and it terminates behind the siding/stucco. This provides a direct path for water to flow behind the wall surface and into the building. Often this type of leak takes time to show and may only be noticeable in heavy rains and the wall needs to soak enough to be evident. The only correct way to repair this issue is to add a layer of flat roof membrane over the existing flashing that directs water flow out and away from the wall. Some roofers may suggest cutting out the old flashings and installing new. We do not suggest this, as it is impossible to replace the wall surfacing material and regain integrity.

Flashing Seams Separating

Flashing seams must be overlapped correctly and an adequate amount of sealant placed in between the overlap area to ensure proper waterproofing at the ell flashing transition area. Here we found ell flashing seams were separating and in need of additional sealant. The correct way to repair this area is to replace the flashing with new. That is the only way to ensure the flashing detail area will not leak.

No Wall Cap/Coupling

Separation firewalls are designed to extend past the flat roof level and protect against spreading flames in the unlikely event of a fire. Many times these walls are simply stuccoed and painted. Over time the paint deteriorates, often at rates faster than walls due to the direct sunlight they receive, and allow moisture to seep into the wall’s core. Under a maintenance program with Sumner Roofing these wall caps can be coated using an elastomeric paint sealant. Other times it is best to use some type of wall cap to permately protect the wall top area. When moisture enters the wall it causes moisture bleed out and swelling. The additional moisture content is trapped and cannot evaporate causing further damages to fasteners, flashings and framing. The swelling can rust out concrete rebar and steel straps, both structural components of the wall. The correct way to fix this is to treat the wall top as a roof and install a roof system on it. This can be achieved by installing a metal coupling or a flat roof membrane with flashing on all four sides of the wall’s top. The flat roof membrane is a better detail as it provides one continuous piece and protection without added maintenance.

Pitch Transition not Flashed

Whenever two different roof pitches transition a specially designed flashing is needed to bridge the slope change. This Millersville roof pitch transition does not have the correct flashing and is relying on sealant to disallow seepage. Over time the sealant will deteriorate and allow leaks. The pitch transition on this roof does not have any flashing in it. Eventually the roofing materials and mastic used to seal this area will cause interior damages.

Counter Flashing Loose

Counter flashing is metal flashing installed into the wall to protect the roof membrane from coming loose from the wall as it transitions from the roof area. Counter flashing can also be used in conjunction with ell flashing at the same detail area. On this Windsor Park roof the counter flashing, which has a concealed return flashing cut and installed into the wall, has come loose from the wall and is allowing water to enter. Counter flashing is an older flashing technique and requires constant maintenance by re-fastening and re-sealing the top wall cut to disallow seepage. This area should be repaired before interior damage occurs.

Metals Touching

When two different types of metals, fair and unfair as they are called, come in contact a chemical reaction occurs. Electrolysis uses moisture as catalysis at a molecular level to pass ions from one metal to the other. The process causes a deterioration of both metals similar to the effects of rust. Using two different types of metal causes electrolysis and the rapid breakdown of metal.

Pan Roof Tie-In Not Correct

Aluminum structures are inexpensive and easy to install. They often add value to a building by providing additional usable space. The flat roofing system is typically a pan or super-pan type made of aluminum and coated white. Insulation is sometimes used to help insulate and dampen rain patter. Pan roofs are large and lightweight. They are often fastened directly to the fascia board of a germinate structure and sealed with a simple bead of silicone caulk. During even light winds the entire structure moves causing the caulk bead to break and open and area for water to penetrate causing seepage at the tie-in and along the ribs. Since the caulking will not reseal it is our suggestion that a transition flat roof membrane be used to cover the tie-in area as would be installed on a normal flat roof tie-in. This will prevent water seepage and stop the fascia board from rotting.

Shingle Granules Loss

Asphalt does not hold up to direct UV exposure. Modified membrane use small white colored stone chips called granules to protect the asphalt from environmental elements and to provide an esthetically pleasing look. Over time these shingle granules wear off. When this occurs the asphalt surfacing starts to break down causing a downward turn in the roof’s life. This is the reason why it is not recommended to pressure clean a modified roof. Pressure dislodges the granules from their asphalt embedment. It is also important to keep overhanging trees trimmed so they don’t brush off granules.

Fiberglass Intermat Showing

Modified membrane construction starts with a fiberglass intermat. During production the fiberglass intermat is saturated with asphalt and dried repeatedly until the desired thickness is achieved. This intermat is not a waterproofing layer but is necessary to keep the membrane from cracking and separating. Over time the membrane surface wears down. Eventually the intermat will become exposed. It is generally accepted that when this occurs it is time to replace the roof. Without the fiberglass intermat holding the membrane construction together the membrane can no longer withstand thermal shock (expansion and contraction) and will crack, possibly allowing seepage.

Flat: Sprayed Polyurethane Foam

Sprayed Polyurethane Foam (SPF) roofs are new to the lineup and are designed primarily as an insulator, not a waterproofing roof system. The top applied coating is the true waterproofing agent and must be recoated yearly to keep the system’s integrity.

Torn/Cracked/Broken Surface

As a roof expands and contracts the roof system moves. This is a daily occurrence and is associated with Thermal Shock. During movement the SPF binds against each other. Sometimes a tree branch or flying debris may impact the roof causing damage. 3rd party damage is another issue. As people walk across the roof they can cause damage. Birds are a particular problem with SPF roofs. They love to poke holes and nest in the surface. The SPF Foam on roof has been damaged. Since this leaves the underlayment showing, it is our recommendation these areas are repaired.

Roof Recovered Offset Not Correct

SPF Foam is not a waterproofing material. When installed correctly, with a heavy waterproof coating and a slight pitch, it does “shed” water. However, SPF foam has millions of small holes called air pockets created at the time of installation. These holes give SPF its insulating properties. As the coating breaks down and allows water into the system the moisture is trapped and causes seepage. We do not suggest spending money on yearly coatings. It is advisable to save funds and replace the SPF roof with a certified roofing system.

Improper Number of Fasteners

SPF roofs are designed to be installed over an approved surfacing fastened to specific guidelines. If SPF roof is installed over a surface without the proper fastening the manufacturer’s warranty is voided and the roof assembly is out of code. This also leaves the roof susceptible to roof blow-off in the event of strong winds.  In 1994, when a new code system was introduced, the requirements became much more strict. However, most of the good roofing contractors go above code and install more fasteners than required due to lessons learned after the storms prior to installing the SPF system.

Tar & Gravel Roof Repair

Tar & Gravel roofs have been around for centuries. Constructed by layering asphalt and felt then finishing the system with a heavy coat of asphalt and gravel, these systems are used primarily on large commercial flat roof area. Tar & Gravel usage has been replaced with more effective modern systems.

Torn/Cracked/Broken Surface

As a flat roof expands and contracts the roof system moves. This is a daily occurrence and is associated with Thermal Shock. During movement the flat roof membrane binds against each other. Sometimes a tree branch or flying debris may impact the flat roof causing damage. 3rd party damage is another issue. As people walk across the roof they can cause damage. The membrane on this roof has been damaged. Since this leaves the underlayment showing, it is our recommendation these areas are repaired.

Fiberglass Intermat Showing

Tar & Gravel roof construction starts with layers of fiberglass felt paper and asphalt. This intermat is not a waterproofing layer until it is layered with asphalt and more fiberglasses felt paper. Over time the membrane surface wears down. Eventually the fiberglass felt will become exposed. It is generally accepted that when this occurs it is time to replace the roof. Without the fiberglass intermat holding the roof’s waterproofing construction together the membrane can no longer withstand thermal shock (expansion and contraction) and will crack, possibly allowing seepage.