Terminations and Counterflashing: Stopping Leaks Above the Roof

It never amazes me anymore how many ways a detail can go wrong. This past summer on a large mechanically fastened roof whose construction I was observing, I walked up to the parapet walls and, after using my binoculars, I was finally able to spot the bead of water block somewhere near the top of the wall. (See Photo 1.) Now, I know my idea of a sealant bead might be different from that of the local roofing crew, but not by a 1,000 percent.

Photo 1. Can you spot the water block in this photo?

Not only was the bead far too small, it was not in the correct location and had been exposed so long that it was hard. Apparently the thinking was, “You can install the termination bar days or weeks later on an inclement day.” I don’t even get upset at issues like this anymore because I wield the money, and my policy is this: “You can do it your way, or you can do the way that will get you paid.”

The proper installation of termination bars on what I refer to as hard surfaces — that is, non-organic walls — isn’t rocket science, but takes some thought. Considerations should include things like, “Wouldn’t it be nice if they were installed straight?”

In my opinion — and you know I am correct — a termination bar should never be installed without counterflashing. Do not leave the T-bar naked to the elements to save a few cents. I know some manufacturers erroneously allow it, but that’s only because the other guys do, and that hardly seems like a good reason to me, but rather just another marketing design decision.

Photo 2. Did the architect really believe this aged masonry wall was watertight?

As hard surfaces on these projects, I typically see brick masonry (not CMU — you as a designer wouldn’t be numbskulled enough the leave an exposed CMU wall, would you? And no, paint or a coating doesn’t make it unexposed). Precast and tilt-up concrete are also commonly used.

There are issues and nuances with each type of surface that need to be taken into account when detailing and installing the roof system, including the substrate condition, masonry control joints, concrete joints and their shape, and interior corners where all the expansion and construction occurs. Issues to design with each substrate condition are outlined below.

Masonry Walls

Photo 3. This was actually designed by a consultant. Note the water on the vertical wall behind the membrane. The stick ruler points to the through-wall flashing. At least one of these components is doing its job.

Placing a termination bar and counterflashing on substandard masonry walls may look good but will not prevent water intrusion.

• Masonry inspection: Check any masonry above the roof and, if necessary, include masonry restoration as part of the project. Yes, before the new roof is installed, be sure the masonry behind the two, three or four layers of base flashing is included.

• Weeps and through-wall flashing: Do I have to say it? Don’t cover them. (See Photo 3.) If they are too low for the new insulation height, raise the through wall-flashing. Yes, you will need a detail for this.

• Control joints: I always enjoy walking a new roof and seeing the sealant control joint on the high wall above the roof wide open. How many times will the roofer be out looking for the roof leak?

• Expansion joints: Trust me, all materials move IN and OUT. I have seen copper gutters ripped in half. Design the termination bar and counterflashing to float over these movement joints.

Concrete: Precast and Tilt-up Panels

Photo 4. The challenge with precast joints is that they are beveled. This makes sealing them a challenge. Note that the reglet cut doesn’t even extend as far back as the sealant. Note also the cohesive failure of the sealant in the joint.

It used to be that you would only see precast wall panels; now the big guys are pouring tilt-up panels right onsite. I like the tilt-up better. Precast typically has a chamfer interior side joint (See Photo 4) that no one details to be caulked flush with the precast. This leaves an open void behind the base flashing and is difficult to cross with a termination bar and counterflashing — most just “gook it up” and pray. Tilt-up often has square joints that are much easier to seal, provided the caulker gets there before the roofer. If the joint is chamfered and not sealed flush, a second piece of sheet metal needs to be cut in above the counterflashing that projects back behind the sealant, so that should the sealant fail, water is caught by this piece. (See Figures 1A and 1B.)

Figures 1A and 1B. When there is a beveled precast joint, the method of sealing the counterflashing at the joint needs to be considered and detailed. Here a closure piece with a round return to match the grinder radius is inserted up behind the expansion joint.

As with masonry, the termination bar and counterflashing should be detailed.

• Interior corner: The mass in precast panels is substantial, and when they move under temperature fluctuations the accumulated movement has to be taken somewhere — and that is the corners. (See Photos 5A and 5B.)

Photos 5A and 5B. There is a tremendous amount of movement at the corners of tilt-up and precast concrete panels. Not only should the sealant joint be able to handle this movement, the termination bar and counterflashing over them also need to be designed appropriately.

• Joint detailing: It no longer surprises me when a simple sealant joint is asked to protect the interior with thick concrete walls. To make matters worse, the sealant used is often a poor-quality product with a short service life. When I hear people say, “That’s okay because we will come back a few years later and replace it,” I always respond: “Why use one, when we can use two?”

The details in Figure 1 demonstrate how we add a redundant layer of protection: a double sealant joint. If you can, try to get this detail in the initial construction drawing. I know you’ll probably get a “Why?” like I do when I suggest on cold storage buildings to caulk both joints in the metal panel. Why? Because most building owners do not like seeing water run down the joints, and in the case of the metal wall panels, large ice formations on the wall panel joints.

Getting it Right in the Office and in the Field

Photo 5B

Continuing with our checklist approach, included with this article is a step-by-step quality assurance checklist for use by those in the office and in the field.

Too much moisture intrusion is occurring above the roof plane because of a lack of detail, manufacturers’ low-end minimums that architects design to, and poor workmanship. Spending a little time verifying existing conditions, designing to the conditions, and then following up in the field will eliminate those phantom leaks — and allow you to investigate the fun ones under the RTU a whopping foot above the roof.

Happy roofing.

Figure 2. A double sealant joint on the exterior side of the precast/tilt-up with a high-quality sealant will provide great protection from the elements for decades.
Figure 3. A quality termination bar and counterflashing detail sets the stage for expectations.

About the author: Thomas W. Hutchinson, AIA, CSI, Fellow-IIBEC, RRC, is a principal of Hutchinson Design Group Ltd. in Barrington, Illinois. For more information about the company, visit hutchinsondesigngroup.com.

Quality Assurance Compliance:

Terminations and Counterflashing For Hard Surface Wall Substrates


Masonry Walls

1. Does the masonry wall above the roof to be replaced require restoration?

o Yes o No

2. Do weeps and through-wall flashing exist, and if so, will they be affected by the new roofing height? (If so, design raised new through-wall flashing system.)

o Yes o No

3. Do control joints and/or expansion joints exist?

o Yes o No

4. For aged, solid masonry parapet walls, consider an air/drainage mat covered by a substrate board.

5. Have all foreign contaminants, anchors, and protrusions been removed?

o Yes o No

Precast/Tilt-Up Concrete

1. Are the joints are chamfered or square?

2. Design sealant joint flush.

Termination Bar Design

1. The termination bar should be not less than 1/8” thick (and thicker if conditions require).

2. Is anchoring the bar at 12” on center (o.c.) great enough to compress the bar to the substrate between the anchors? (If not, increase spacing.)

o Yes o No

3. Design and detail termination bar spacing at expansion joints (and interior corners on precast/tilt-up).

4. For continuity of a sealing mastic between the substrate and membrane, consider designing and detailing the use of a continuous 3/16” x 1” butyl caulk tape. The butyl will fill in the concave vertical brick mortar joints.

5. Mandate that the termination bar is to be installed on the same day at the base flashing.

6. Call for the roof base flashing to be run horizontally across the wall starting at the high point.

7. Is the counterflashing surface mounted? (The author prefers the surface mounted over the reglet type [see Figure 3.])

o Yes o No

8. For continuity of a sealing mastic between the substrate and counterflashing designing and detailing, the use of a continuous 3/16” x 3/4” butyl caulk tape to be placed on the backside of the vertical anchor areas on the counterflashing. This will fill in the concave vertical mortar joints. Call for 5/16” pre-drilled pilot holes at 12” o.c. or spacing as noted.

9. Is anchoring the counterflashing at 12” o.c. great enough to compress the counterflashing to the substrate between the anchors? (If not, increase spacing.)

o Yes o No

10. For copper, call for a brass bar to be placed on the counterflashing and the anchors passed through the bar.

11. Did you design and detail counterflashing spacing at expansion joints (and interior corners on precast/tilt-up)?

o Yes o No


1. On existing masonry walls if required, has the appropriate restoration taken place?

o Yes o No

2. If designed for masonry parapets, have the air/drainage mat and cover board been installed with horizontally level top? Has the top of the cover board been chamfered and secured at 12” o.c. top and bottom staggered?

o Yes o No

3. Has the cover board after installation been protected from moisture contamination?

o Yes o No

4. Has the cover board been covered with fully adhered flashings?

o Yes o No

5. Has the butyl tape or water cut-off mastic been installed at a minimum of a 1/2” bead and/or 10 linear feet per tube behind the base flashings where the termination bar will be installed?

o Yes o No

6. Has the termination bar been installed directly over the water cutoff mastic behind the membrane and anchored at 6”, 9” or 12”?

o Yes o No

7. Has the termination bar been installed on the same day as the base flashing?

o Yes o No

8. Has the termination bar been spaced at expansion joints and locations of anticipated expansion?

o Yes o No

9. Has the projecting roof membrane been trimmed flush with the termination bar and the condition sealed with polyurethane sealant?

o Yes o No

10. Has the continuous polyurethane sealant atop the termination bar been installed on a primed surface and tooled in place?

o Yes o No

11. Does the metal counterflashing have 5/16” predrilled holes at 12” o.c.?

o Yes o No

12. Has butyl caulk tape been placed on the backside of the vertical leg through which fasteners are placed?

o Yes o No

13. Has the metal counterflashing been anchored at 9” or 12” o.c.?

o Yes o No

14. Have the primer and continuous backer rod been installed along the top edge of the counterflashing, in the sealant reservoir prior to applying the polyurethane sealant? Has the sealant been tooled in place to shed water?

o Yes o No

15. Has polyurethane sealant been applied to the entire counterflashing fastener heads?

o Yes o No

About the Author

Thomas W. Hutchinson, AIA, CSI, Fellow-IIBEC, RRC
Thomas W. Hutchinson, AIA, CSI, Fellow-IIBEC, RRC, is principal of Hutchinson Design Group Ltd., Barrington, Ill., and a member of Roofing’s editorial advisory board.

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