Lisø PhD Dissertation Manuscript - NTNU

Figure 11a Poor solution for a £ashing connection to masonry.
Weathering of the sealing compound will gradually allow water
to penetrate behind the £ashing
chimney. A superficial jointing compound will never
provide an effective sealing in such a case. Flashings
that are to be inserted into a slit or notch should be
designed with a water flange (Figure 11b). In the
case of pipes and ventilation shafts, where it is impossible
to finish off flashing in a notch, it is common
practice to use a flange/collar.
Leaks frequently occur because work has been abandoned
in a half-finished state. In the case shown in
Figure 11c, a top flashing is missing. A recommended
solution is shown in Figure 11d. Another culprit
Figure 11b Flashing inserted in a notch with a water £ange.The
notch should be a minimum of 5 mm high and 20 mm deep
Figure 11c Collars without protective £ashing can give rise to
severe leakage. A perforation in the £ange transition, as in this
case, makes the situation even worse. Source: Norwegian
Building Research Institute,Oslo
High-performance weather-protective £ashings
Figure 11d Example showing completed roo¢ng-in of a pipe.
Source: NBI (1991)
when it comes to leakage points at openings are the
corners of a chimney flashing. Again, the use of
folded welts is the preferred method of executing
corners (Figure 12). Chimney flashing joints should
not be executed with overlapping joints.
Gable, abutment and valley gutters
Few problems with gable, abutment or valley gutters
have been registered. Most of the problems are
Figure 12 Recommended design of foot £ashing for a brick
chimney in sheltered areas
51