1-805-557-1225

If We Made Waterproofing Any Easier, It Would Be Embarrassing.

Home > Press Room > Waterproofing Pipe Penetrations Western Roofing

Waterproofing Pipe Penetrations
A New Solution

by Lawrence Evensen

Building plans and specifications are the concise narrative detailing the design and construction of a project. The goal of the writer is to create comprehensively written documents that tell the building story. Unfortunately, many plans and specifications leave out enough details that they read more like a Sherlock Holmes or Nancy Drew mystery novel, but without the "gotcha" finale, which ties up the loose ends. This is particularly true with specifications for roof penetrations.

The mystery is what product will provide a watertight assembly for each of the various penetrations shown on the roof plan. Without detailed specifications, the story is incomplete and the roofing contractor is left holding the bag. An understanding of roof flashings and counter flashings, and how they perform their waterproofing tasks is necessary. The following paragraphs concentrate on roof penetrations and the methods of installing flashings and counter flashings to aid in comprehensive roof plans. The end result is a smoother running construction project.

Over the centuries, roof construction has evolved to include two waterproofing techniques, flashings and counter flashings. Flashings and counter flashings create a rise in the roof's membrane that is high enough to keep the elements from entering the waterproofing membrane, and then place a cover over the rise.

The roof rise feature, or flashing, will facilitate water run-off as long as the weather conditions are not extreme enough to overflow the rise. The cover of the flashing, or counter flashing, is designed to allow water to shed over or around the flashing opening.

There are many classes of roof flashings and counter flashings, including but not limed to, base flashings, chimney flashings, coping flashings, eave and fascia flashings, valley flashings and roof penetration flashings.

For each class of flashing, the law of gravity and the rules of physics for the flow of water is the same. The roof flashing is constructed to rise higher than the highest expected water level from a weather event, and it is counter flashed to cap the opening of the flashing, allowing gravity to direct the water away from the flashing opening.

Flashings for roof penetrations, projections, and equipment stands are designed with the flashing/counter flashing design described above. Pipes, conduits, vents and support legs use a sleeve or "jack" flashing to create the rise in the roof's level.

ALTERNATE ROOF PENETRATION FLASHING DETAIL - CLICK IMAGE TO ENLARGE

As a general rule of thumb, roofing product manufacturers follow the guidelines of the National Roofing Contractor's Association (NRCA), which recommends using a metal flashing or the insertion of roof jacks into the membrane for projections through the roof's membrane not lower than 8", and not higher than 14" above the finished roof level on low slope roof applications.

Steep slope roof applications can have a rise as minimal as 2.5 to 3", since the roof slope will guarantee that a water event will not be high enough to overflow the flashing even in extreme weather conditions.

Many penetrations through a roof covering can be waterproofed using the respective manufacturer's standard details. Round penetrations, such as plumbing vents, electrical conduits, HVAC chiller lines, domestic water lines, natural gas and other pipes, can be matched to a pipe flashing jack with the proper outside diameter. Nearly all designers call out a flashing method at these locations. It's the responsibility of the general contractor to make the appropriate subcontractor responsible for providing the properly sized flashing for each of the roof penetrations on a new construction or remodeling project.

However, when the roof penetration is not a standard round geometry, or when sub trades do not provide the necessary flashing as part of their work, the roofing professional is forced to create a waterproofing detail on the fly. This is complicated by the great variety of structures and mechanical devices used on a roof.

An example is equipment screen support posts. On many structures, equipment that is located on the roof's structure is hidden behind a screen. The screens are structures capable of withstanding high wind loads and are therefore built out of very solid material.

Steel Structural
Square Tube

It is not unusual for equipment screens to employ several hundred roof penetrations made from square, angle iron or H-beam steel. The use of non-round steel support structures at these locations makes standard details difficult to write, creating a problem for the roofing contractor that is difficult to solve.

St. Luke's Outpatient Center is a new medical building located in St. Louis, Missouri. In late 2007, Ryan Freeman, the job superintendent of McCarthy Building Companies, Inc., of St. Louis, discovered that the roof details provided by the roofing material's manufacturer were inadequate. He was faced with 120 4" and 6" square steel support posts that were part of the equipment screen and, if not properly waterproofed, would leak.

The flashing detail included a site fabricated flashing to be created by the roofing crew out of the white single-ply roof product. The plan was to make the flashing, caulk the top edge against the steel post and draw it tight using a stainless steel band clamp. The problem with this technique is that no matter how much torque is applied to the clamp, there will be loose gaps on the flat part of the square post, since square pegs do not fit in round holes.

In search of a better solution, Freeman contacted Ron Carter of RNC Enterprises. Ron is a local vendor providing technical assistance and innovative construction products. Carter suggested installing storm collars over the field-fabricated flashings to provide the necessary waterproofing that each square post required. The steel support posts had already been installed so any counter flashing would need to be a retrofit design. Carter knew that the NRCA approves storm collars for this design purpose.

"The collars have corrected the issue we had with all of our square tube steel colunmns. We have been very pleased and I have recommended this product to many colleagues." -Ryan Freeman, McCarthy Building Companies, Inc.

Choosing a product was his next challenge. Any storm collar used for these posts had to fit the following design criteria:

1. The storm collar needed to be a retrofit design since the equipment screen posts had aleady been installed.
2. The storm collar should be installed using the existing roofing crew labor.
3. The storm collar needed to be made of a material compatible with the metal posts, without worry of corrosion to the post or structure.
4. Sharp dangerous edges would not be allowed.
5. The storm collar should be able to spring back into place in the event of disturbance by workers or pedestrians walking on the roof.
6. The storm collar must have an appearance that enhances the building and conforms to the white roof covering.
7. The storm collars must have a life expectancy of at least 20 years, the life expectancy of the roof.

Fortunately, one of the products that RNC stocks and supplies was a perfect match for each of the design criteria. Retro-Split Storm Collars made of EPDM rubber would create an ideal counter flashing. By ordering the collars with square cutouts sized exactly to match the 4" and 6" metal posts, the storm collars would be a perfect fit for the field fabricated roof detail.

Additionally, the factory-made rubber storm collars open up to wrap around a multitude of geometric shapes. To install the storm collars, a laborer simply uses a nut driver. There is no corrosion compatibility or sharp edges to worry about. If the rubber is impacted by pedestrian traffic, it bends and springs back automatically. Storm collars are even available in white EPDM rubber, which matched the single-ply roofing product installed on the medical center, creating the desired appearance.

"The Retro-Split Storm Collars provide complete waterproofing for a very complex series of roof-top screening supports," said Carter.

By utilizing innovative form fitting storm collars as counter flashings, roofing professionals can solve almost all roof penetration problems easily, economically and confidently. In fact, all roof penetration shapes can be surrounded by "off the shelf" roof flashing jacks that create the rise in roof level on the roof's membrane.

Remember, the NRCA recommends using a metal flashing or the insertion of roof jacks into the membrane for projections through the roof membrane that are not lower than 8" and not higher than 14" above the finished roof level.

These flashing jacks can be fabricated from many classes of materials including lead, steel, aluminum and even single-ply materials. All that is required is a storm collar that attaches to the penetration, or group of penetrations, which acts as the counter flashing over the top of the flashing jack.

The installation of the Retro-Split Storm Collars to solve the building's waterproofing problem is a great example of how an innovative product can improve roof penetration details. By adding these storm collars to the roof plan, each penetration becomes manageable, taking the mystery out of inadequately written details. Case solved.

Contact a distributor today»

If We Made Waterproofing Any Easier, It Would Be Embarrassing.

Waterproofing Pipe Penetrations A New Solution

Waterproofing Pipe Penetrations
A New Solution