How do I fix a leaking shed roof?
Finding where a shed roof leaks, patching felt, and when to re-felt the whole roof instead.
- Difficulty
- intermediate
- Time
- 3 hr
- Read
- 2 min
- Safety
- caution
Short answer
Find the leak from inside on a wet day — water tracks along timber, so the wet patch is rarely under the hole. Small tears patch with felt adhesive and a felt offcut; widespread cracking or bubbling means the felt has reached the end of its life and needs replacing.
Shed roofs leak because roofing felt has a limited life — typically ten to fifteen years — and fails at the ridge, the edges and where fixings penetrate it. Patching buys time on an otherwise sound roof; on a brittle, cracked one it is a waste of an afternoon.
Safety
What you'll need
- Roofing felt offcut or a roll
- Felt adhesive
- Clout nails
- Stanley knife
- Stiff brush
- Ladder (optional)
Step by step
- Go inside on a wet day and look for where water actually enters.Water runs along rafters before dripping, so mark the entry point rather than the drip point.
- Inspect the felt from outside, paying attention to the ridge, edges and around fixings.Those three account for most shed roof leaks.
- Assess whether the felt is patchable or finished.Isolated tears on otherwise supple felt: patch. Widespread cracking, bubbling or brittleness: replace.
- For a patch, clean and dry the area and brush off loose grit.Adhesive will not bond to a dirty or damp surface.
- Cut a felt patch overlapping the damage by at least 75mm all round.Generous overlap is what makes the patch hold.
- Apply felt adhesive to both surfaces, press the patch down firmly and work outwards.Working from the centre out expels air. Weight it down while it sets if you can.
- For a full re-felt, strip the old felt, check the boards underneath and replace any rotten ones.New felt over rotten boards fails quickly. This is the moment to fix them.
- Lay new felt from the bottom up, overlapping each sheet over the one below.Bottom-up with overlaps so water runs over joints rather than into them. Nail at the edges, not through the middle of the run.
Tips
- Overhanging branches shorten felt life considerably by keeping the roof damp and dropping debris. Cutting them back is worth doing.
- Check shed felt every autumn while you are clearing gutters — it is easy to catch a small tear before it becomes an interior soaking.
- Consider a more durable covering than standard felt if you are replacing it — the extra cost is small relative to doing the job again in ten years.
Common mistakes
- Standing on the shed roof — Most shed roofs will not take an adult's weight and you go through it.
- Patching brittle, widely cracked felt — The next leak appears somewhere else within months. At that point re-felting is the real answer.
- Laying new felt from the top down — Water runs into the overlaps instead of over them. Always work bottom-up.
Questions people ask
How long does shed roofing felt last?
Typically ten to fifteen years, less if the shed is shaded and damp or under overhanging trees. Brittleness and widespread cracking are the signs it has reached the end rather than just being damaged.
Why is the leak not where the water drips?
Water runs along the underside of rafters and boards before falling. Trace it back uphill from the drip to find the actual entry point.