A roof valley is the channel where two roof slopes meet. It gathers water from both sides and carries it towards a gutter, so a restriction can affect more than the narrow strip you see. A valley leak should be assessed as a flow problem as well as a possible hole in the metal.
Three different faults can look like one leak
Leaves, moss and silt can restrict a sound channel and push water sideways beneath adjacent roofing. Corrosion can create pinholes or splits in the valley pan itself. Poorly arranged tile edges, insufficient channel capacity or an awkward outlet can cause overflow even after debris is cleared. These need different scopes, not the same sealant treatment.
The outlet matters too. A valley may deliver water correctly but overshoot or back up where it meets a gutter. If the downstream gutter or outlet is restricted, renewing the valley alone may not stop the internal stain. Ask where the water is intended to go from the top of the valley all the way to discharge.
Warning signs to record safely
- A stain near the junction of two roof slopes, especially during prolonged rain.
- Visible leaf accumulation in a valley when viewed from ground level.
- Rust marks or debris arriving at the gutter below the valley.
- A leak that returns soon after a gutter clean because the valley itself was not inspected.
None of these proves the source. Water can travel beneath the roof covering, and nearby flashings may also leak. Do not walk up the valley or lift tiles to check: narrow channels, slippery debris and unsupported tile edges make this unsafe.
A roof valley leak repair assessment should distinguish blocked flow from failed metal and check how the surrounding tiles or sheets connect to the channel.
When clearing is enough, and when it is not
If the metal is sound and debris is the only restriction, professional clearing and correction of an obstruction may be enough. The roofer should still check for corrosion beneath retained material and show how access for future cleaning will work. Repeated blockage may need a different maintenance interval rather than an unnecessary replacement.
Where a pan is perforated or broadly thinned by corrosion, a small patch may leave adjacent weak metal in service. Replacement may be more suitable. It involves disturbing roofing on both sides and integrating new metal with underlay and the gutter, not simply laying a new strip over a wet, rusted channel.
Questions for the written scope
Ask which valley run is included, whether adjacent tiles need replacing and how material compatibility will be checked. The scope should identify any changes to the outlet or gutter, provisions for temporary weather protection and how concealed timber damage will be handled if found. There is no single pan size or tile spacing suitable for every roof.
At handover, request photographs of the channel and its outlet before surrounding roofing conceals the edges. Confirm what was cleared, replaced or retained and what inspection is recommended after heavy leaf fall. This makes future maintenance more specific than a general instruction to keep the roof clean.
Check the whole valley water path
The useful decision is whether your valley needs clearing, corrected detailing or new metalwork—not another unexplained patch.
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