- When detailing a condition that affects other conditions, it is best to draw it at the area of greatest issue: For example, for the tapered insulation saddle condition, draw the details at the ridge.
- The proper termination of the roofing at the base of the wall should be shown, not a single line running up the wall. What secures the membrane should be shown, and the spacing of anchors should be noted.
- The base flashing should be shown extending up to the bottom of the counterflashing receiver; a water block and termination bar also should be shown. Yes, detail these components and, while you are at it, note how often the termination bar is to be “pinned” and with what type of anchor: expansion anchor, masonry screw anchor, etc.
- Because this condition contains a good deal of important information in a small area, it might be best to “bubble” it out to show all the components.
When completed, this detail has provided an appropriate interface be- tween two very important building envelope systems (see Detail 3). Photos 3 and 4 show a recent project.
ROOFING REMOVAL AND REPLACEMENT CONSTRUCTION
With the advent of increased required thermal insulation and the emphasis on tapered insulation to remove water from the roof as quickly as possible, designers are often presented with new insulation heights well above existing through-wall flashing conditions. Two design options are available to correct the condition that exists:
1. Raise the through-wall flashing.
2. Design an interior gutter and allow the existing through-wall flashing to remain.
Option 1 is certainly the more often accomplished detail. I designed option 2 a couple decades ago and it still is working (see Photo 5). I mention it so you have this solution in your design repertoire.As with all reroofing work, test cuts of the existing roof system should be taken to determine not only the existing roof’s composition and roof deck type, but also to determine the depth of the existing roof(s), so the required height of the new through-wall flashing can be determined.
The same exercise shown in the examples in the “New Construction” subhead, page 1, needs to be undertaken so that you have a handle on the roof insulation heights. Photos 6 through 9 are from a recent project and show how this work is undertaken.
Prior to detailing, the exterior wall components should be determined. As with the roofing, this is best done through an exploratory opening.
The final detail will look much like the one for new construction but with many components labeled as “existing”. A demolition detail should be prepared showing the extent of brick removal (see Detail 1). Although this can be done in a building elevation, we find photos with notes work well. The drafted detail should express new materials versus existing. This is most often done by ghost outlining existing materials with new materials being dark lined with
material poche (see Detail 2).
As with new construction, coordination is critical because now the interior of the building needs to be dry. With our reroofing projects, the roofing contractor typically assumes the role of the “prime” contractor and, thus, has supervisory control over his subcontractors. So roofing contractors are not searching “Angie’s List” for masons, we often have this work under an allowance and assign the mason to the roofing contractor after the contract is awarded. This prevents non-qualified contractors from being involved and raises the quality of workmanship.
THE DEVIL IS IN THE DETAILS
“Do it right the first time” is the perfect mantra for design and construction of the interface of roof base flashing and masonry through-wall systems. When not detailed and left to the contractor’s whims, the resulting moisture intrusion is difficult to determine, correct, expensive and leaves owners questioning your abilities. But thinking of the interface of roofing and masonry walls holistically, one can perhaps see the concerns, design for them and delineate them so that the crews in the field can accomplish them.
IMAGES: Hutchinson Design Group Ltd.