When a roof starts to leak, it is almost never because of the slope itself: it is because of one of the flashings, the points where the roof changes direction or meets another element. That's where the most care is needed, not on the flat surface of the roof.
Hip and valley: they're not the same
Both are special pieces for the angled meeting of two roof slopes:
- Hip (external angle): the water splits to both sides.
- Valley (internal angle): concentrates much more water than the rest of the slope, because it collects that of both slopes.
The valley is by far the point where the most leaks appear over time. Always check it has enough cross-section and a clear fall towards the gutter — it is not an aesthetic detail, it is the piece that handles the largest water flow of the whole roof.
Flashing: the metal finish, not silicone
The flashing or perimeter finish is the metal piece that seals the junction between the roof and a vertical element: chimney, wall, skylight or aerial. It is one of the points with the most leaks on the whole roof, precisely because it interrupts the continuity of the tile or sheet.
Never solve it with silicone alone: well-lapped metal flashing is the durable solution; silicone is a spot reinforcement, not the system itself. Relying only on silicone at this point is a temporary fix that fails within a few years.
Ridge: the point most exposed to wind
The ridge caps the upper junction between two slopes, at the highest line of the roof. Always fix it with mortar or a specific clip according to the manufacturer's system — a poorly fixed ridge is among the first elements to shift in strong wind, precisely because it is at the most exposed point of the roof.
Frequently asked questions
What is the practical difference between a hip and a valley? The hip is on an external angle and splits the water; the valley is on an internal angle and concentrates the water of both slopes, making it the point most prone to leaks.
Can I seal a chimney junction with silicone alone? It is not the durable solution: well-lapped metal flashing is the real system; silicone should be used only as spot reinforcement, not as a substitute for the finish.
Why does the ridge shift in the wind? Because it is at the most exposed point of the whole roof. If it is not fixed with mortar or a specific clip according to the manufacturer's system, it is among the first elements to move in strong gusts.
Conclusion
The finishes of a roof —valley, flashing, ridge— concentrate more risk of leaks and displacement than the flat slope, and deserve as much technical care as the covering material itself. Quoting them with the right margin and system, without silicone shortcuts, is what prevents the roof from starting to give trouble after a few years.
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