- Q.I am installing steel roofing panels with
exposed fasteners. Where it is necessary to install two panels
between the ridge and the eaves, how much should the panels
A.Daniel C. Jandzio, wood frame product manager
at Fabral, a metal roofing manufacturer, responds: A good
rule of thumb for end-lapped panels is to use a 12-inch endlap.
If the metal is going over purlins, or nailers, lay out the
panel lengths so that the lap occurs over the support. The
bottom panel should be long enough to allow for a 1-inch eaves
overhang and extend about 6 to 7 inches past the upslope edge
of the endlap support. The top panel should extend 2 inches
past the downslope edge of the endlap support.
To prevent leaks, always install the fasteners 3 to 3 1/2
inches up from the end of the overlapping panel, and apply a
bead of butyl sealant just downslope of the fasteners (between
the weather and the fasteners). I prefer pre-extruded butyl
3/32x1 inch wide. This product is inexpensive, easy to
apply, and doesn’t hold the panels apart (causing
fish-mouthing) at the panel lap. Butyl sealant doesn’t
cure and will remain tacky for the life of the roof.