DETAIL 1: FOUNDATION TO FRAMED WALL

Foundation walls and wood framing are typically aligned with each other in the same plane. The seam between the wood and foundation construction is a weak point in air and water barrier continuity that needs to be addressed. While sill sealers are common, their effectiveness can vary. Further, flashing is often needed at this joint to assure that water, which finds its way down the face of the sheathing, has a place to safely exit out and away from the wall assembly. A typical detail showing a flashed wood-framed wall on a concrete slab foundation is shown in the above diagram. The image on the bottom left shows a wood-framed floor resting on a CMU foundation wall with the wall sheathing extending past the floor structure down to the top of the CMU in typical fashion. At the wall/foundation joint, metal flashing is installed to direct water away. Using integrated sheathing in this case means that the sheathing surface provides a continuous air and water barrier to the end of the sheathing. By also providing self-adhering tape over the metal flashing (effectively acting as counter flashing), the joint is sealed along the top of the flashing, assuring that water and air do not penetrate along this top flashing edge. Placing sealant under the flashing will further strengthen the seal along this joint. The foundation should then be treated with separate coatings to assure that it meets the criteria for water and air resistance. In this way, all water and air barriers are run up to each other and are indeed continuous.

An alternative is shown in the image on the bottom right using liquid flashing. In this case, the framing is adjusted so that the outer face of the sheathing is aligned with the outer face of the foundation wall. This would allow for continuous insulation to run up from the foundation, continue past the floor framing, and up along the wall, thus creating a truly continuous insulation condition. However, the joint where the wood framing meets the foundation wall still needs attention to be sure that any wayward air or water does not penetrate. In this case, liquid flashing can be applied as a coating across the joint and assure the continuity.

DETAIL 2: FRAMED WALL INTERSECTION WITH CONCRETE/MASONRY

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This is an example of a change in materials occurring not in a continuous plane but at intersecting planes. This could occur in any number of circumstances, but the point is that if a framed exterior wall abuts a concrete or masonry exterior wall, then all barriers need to be assured of continuity. The weak point is clearly the point of intersection shown in plan view in the diagram at the left and the image on the top right. The image on the bottom right shows a perspective view of the same condition. If this were two intersecting walls using integrated sheathing, then self-adhering tape along the joint would be a logical and effective solution to assure continuity of the air and water barriers. However, such tape is not designed to work with concrete or CMU, but liquid flashing is. Therefore, once an appropriate control joint and backing rod are determined for this detail, then a continuous layer of liquid flashing can be applied in the corner to completely fill and seal the two adjacent surfaces to each other.

DETAIL 3: MASONRY VENEER

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Using masonry veneer over a wood-framed structure is common and offers many appealing benefits. However, it does require attention to the way the masonry and the wood framing and sheathing all work together. A gap or air space is a well-known best practice to use between the back of the masonry and exterior side of the sheathing. This allows any water, moisture, or bulk water that does enter the wall to be stopped and dispersed along the face of the sheathing. That means the sheathing still needs to be specified and shown as fully air and water resistant since the expectation is that it will indeed need to resist both. As the water collects and drains down the face of the sheathing, it needs to collect and have a place to exit the wall. Hence, flashing and weep holes are needed to collect, direct, and expel that water safely. In so doing, the flashing must be installed so it does not compromise the integrity of the barriers either because of fasteners being used or because a joint or seam is caused to remain exposed. Using self-adhering tape along all sheathing joints and seams as discussed for other walls is the first step. Then, locating metal or other flashing as appropriate for the design of the masonry veneer wall needs to be done with an eye toward protecting the integrity of the barriers. Finally, self-adhering tape should be applied across the top of the flashing to assure that no water makes its way behind it and into the wall.

DETAIL 4: WINDOW OPENINGS

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Windows, particularly if they are recessed back into the wall assembly, can be considered an anticipated barrier detail in virtually every wood-framed building. Not only are openings like this a breach in the barriers simply by virtue of their presence, they also constitute one of the most likely places for water and air leaks to happen. Part of the issue here is the common practice of defining a rough opening size that is, by definition, slightly larger than the size of the window unit being installed. That means there is a gap around the window that needs to be addressed. Many windows have mounting flanges that surround the windows and are used as the basis to center, level, and hold the window in place. The surrounding flanges then become the exterior point that need to be sealed to assure the continuity of the air and water barriers. Using integrated sheathing and self-adhering tape is one method. The tape can cover the window opening first and be used as pan flashing. Once the window unit is installed with sealant appropriately applied under the sill, then the tape can be applied vertically along the jambs to seal those edges. Finally, the head can be sealed with tape covering the flange and the jamb tape to assure a complete seal.

For windows recessed into a framed wall, a mounting flange is not typically used. In this case, the entire perimeter of the recess needs to be addressed to extend the barriers from the face of the sheathing, into the framing recess, and to the window. Using liquid flashing along all of these areas as shown in the images above helps assure full and continuous sealing. Along the sill and for at least 6 inches up the sides of the jambs, the flashing should extend all the way from the exterior to the interior face of the wall. When ready, then the window should be installed and secured using sealant and appropriate fasteners.

Regardless of the condition on the outside, the interior of the windows needs the final piece of attention. The visible gap between the rough opening and the window unit needs to be filled with a sealant or spray-foam insulation that will complete the continuity between the exterior barriers and the window unit. Otherwise the gap remains and can allow air, water, or moisture to penetrate from either the exterior or interior.

DETAIL 5: WALL TO ROOF INTERSECTION

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It is common to have a sloped roof over a lower portion of a building abut a vertical wall of a higher portion of the building. In this case, continuous metal flashing or step flashing is typically used to assure that water draining down the face of the wall does not penetrate the joint between it and the roof but instead flows harmlessly away. That should still be done when integrated sheathing is used, but in addition, the top of the flashing should be covered with a continuous run of self-adhering tape. That will seal the edge along the top of the flashing, as done elsewhere, and can help cover any irregularities in the line of the flashing.

DETAIL 6: PARAPET WALLS

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Wood-framed buildings with low-slope roofing systems often use a parapet wall that continues up past the level of the roof and provides the appearance of a “flat roof” on a building. Technically, the parapet portion extends up above the line of the thermal envelope so insulation is often not installed in them. However, if continuous insulation is used, then it should continue to wrap up and around the parapet, extending down to meet the roofing insulation. Further, with or without insulation, the water and air barrier aspects of these walls are still critically needed since they can still be sources of failures and potential damage. The reality is that it is fairly straightforward to assure that these barriers are indeed continuous by simply treating both sides and the top of the parapet wall in a continuous manner. First, the air and water barrier needs to cover the full outside face of the parapet wall, not stop anywhere. At the top, it should extend across the top of the wall (which may only be the thickness of the framing) and back down the interior side to the roof deck. All joints and seams of integrated sheathing used for this purpose over the framing should be taped, just as elsewhere. Then, a sloped top cap can be placed on top of the parapet and the roofing membrane, and/or flashing should also extend up the full face of the interior side of the parapet wall, continue across the top, and lap down over the outside face for at least 12 inches. The exterior cladding or finish material will cover all of this and create the final look, but underneath, all of the barriers remain connected and continuous in this manner.

DETAIL 7: DECKS AND BALCONIES

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Once the building is enclosed, then exterior decks or balconies should be looked at as if they are part of the envelope design. The key point of connection here is the ledger board that is typically installed across the face of the exterior wall to support the framing for the deck or balcony. This should only be done after the integrated sheathing is fully installed, taped, and sealed. Then, the ledger board with any joist hangers can be installed using appropriate fasteners. In some cases, those fasteners can be large and can cause significant damage to the water and air barrier, hence they should be treated like a penetration that is predrilled and sealed first. Then, the appropriate connection can be made and sealed again if needed. Once the ledger board is in place, then the joint between it and the wall needs to be addressed to be sure that the barriers remain protected. This is accomplished with metal flashing that extends from the wall and under the decking or above balcony flooring to channel water appropriately away. The top of the flashing should then be covered with a continuous line of tape.