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Where the water shows up is not where it gets in

Most roof leaks are not holes in the roof. They are a detail — a boot, a flashing, a valley — and where the stain appears is a poor guide to which one.

This works out an answer as you change the controls, which needs JavaScript. Without it, the reference section below covers the same ground, and we are happy to talk it through.

Wind-driven rain at the eave, section CEILING BELOW — WHERE THE STAIN APPEARS UNSEALED COURSE WIND WATER UNDER THE COURSE SELF-ADHERED MEMBRANE stops it reaching the deck WIND-DRIVEN RAIN rain is pushed up the slope, not down it
Fig. 1 Why a roof can leak in a storm and stay dry in a week of steady rain. Wind pushes water up the slope and under a course whose seal has broken, and the self-adhered membrane at the eave is what stands between that and the ceiling. Illustrative section, not a photograph.

How a leak is actually traced

  1. Start in the attic

    Daylight, staining on the underside of the deck, rusted nail tips and wet insulation all point uphill towards where water is getting in.

  2. Follow the water up

    Water runs along rafters and decking before it drops. The entry is uphill of the stain, and on a low-slope run it can be a long way uphill.

  3. Inspect the suspect detail from above

    Once the attic narrows it to a penetration, a wall line or a valley, that detail gets looked at directly and photographed.

  4. Fix the defect, not the symptom

    Replacing a boot, rebuilding a flashing or reworking a valley fixes the cause. Sealant over the top of a defect buys a season.

The usual suspects, in order of how often they turn up

  1. Pipe boots. The rubber collar splits years before the shingles wear out.
  2. Step flashing at a wall or chimney, especially where it has been replaced with a caulked strip.
  3. Valleys, where nails too close to the center line or debris damming the trough both leak.
  4. Counterflashing surface-mounted on masonry instead of let into a cut groove.
  5. Nail pops, which lift the shingle above and leave a hole underneath.
  6. Wind-driven rain, which gets past flashing that sheds ordinary rain perfectly well. On this coast it is the leak with a season.
  7. Condensation off cooled ductwork or a cooled deck, which drips on a dry day and is not a roof leak at all.

If your leak only shows up in a storm and never in steady rain, read hurricane season roof prep before you let anybody sell you a roof. Wind-driven rain enters where ordinary rain does not, and the repair is usually flashing rather than covering.

A leak that has been traced properly is fixed once.

Have it traced

All work is performed by insured local roofing professionals. Texas does not license roofing contractors at state level, so insurance, references and a written scope are what there is to check.

SheetTool
Service areaGreater Houston and the Texas Gulf Coast
Last reviewed24 September 2026