Roof Leak?
Here's How to Find a Roof leak and Fix It, and When to Call a Pro
A roof leak rarely announces itself with a dramatic waterfall through the ceiling. More often, it starts as a small damp patch, a faint musty smell, or a subtle water stain you’ve been meaning to investigate. Left unchecked, even a minor leak can cause serious structural damage, encourage mould growth, and lead to costly repairs down the line.
This guide walks you through everything you need to know — from how to detect a roof leak in the first place, to quick fixes you can do yourself, to understanding when it’s time to pick up the phone and call a qualified roofer.
How to Find a Leak in Your Roof
Before you can fix a roof leak, you need to find it. And that’s often the hardest part. Water is sneaky — it can enter through one point on your roof and travel along rafters or insulation before dripping down somewhere completely different inside your home. This means the stain on your ceiling may not be directly below the source of the problem.
Start Inside: Look for the Signs
The first place to check is your loft or attic space. Grab a torch and look for:
- Water stains or discolouration on rafters, joists, or the underside of the roof deck
- Damp or wet insulation, which will often appear darker and may smell musty
- Mould or mildew growth, particularly in corners or around timber joins
- Daylight visible through the roof, which is a clear sign of a gap or missing material
- Rust stains around nails or fixings, indicating long-term moisture exposure
Move to the Outside: Inspect Your Roof
Once you have a rough idea of where the problem might be, inspect the exterior of your roof from ground level using binoculars, or from a ladder if it's safe to do so. Never walk on a roof unless you're a trained professional — the risk of injury is significant, and you may cause further damage.
Look for:
- Missing, cracked, or curling tiles or slates — these are among the most common causes of roof leaks
- Damaged or missing ridge tiles at the apex of the roof
- Deteriorating or cracked flashing around chimneys, skylights, vents, and dormers — flashing is the metal or lead material that seals these joins, and it's one of the most frequent failure points
- Blocked or sagging gutters — water that can't drain properly can back up under roofing material
- Moss or algae build-up, which can lift tiles over time and allow water ingress
- Cracked or crumbling mortar around chimney stacks or parapet walls
The Hose Test
If you can’t find the source after a visual inspection and there’s no rain forecast, try the hose test. Have a second person inside the loft or watching the ceiling while you slowly run a garden hose over different sections of the roof, working from the bottom upwards. Start below where you suspect the leak and work your way up, soaking each section for a few minutes before moving on. When your helper spots moisture appearing inside, you’ve found your area.
This method takes patience, but it’s one of the most reliable ways to pinpoint a roof leak without waiting for the next downpour.
How to Repair a Roof Leak from the Inside (Temporary Fixes)
If you've found the source of the leak and need to stop water damage while you arrange a proper repair, there are several things you can do from inside your loft to buy yourself some time. These are temporary measures, not permanent solutions — but they can make a real difference in limiting damage.
1. Catch and Redirect Water
Place buckets or containers under any active drip points. Lay down old towels or plastic sheeting to protect stored items and the ceiling below. If water is pooling on the loft floor, a wet/dry vacuum can help remove it quickly.
2. Apply Roofing Tape or Sealant
If you can identify the exact point where water is entering — a crack in the roof deck, a gap around a pipe, or a failed seal — you can apply self-adhesive roofing tape or a waterproof sealant as a short-term fix. Clean and dry the area as much as possible before applying, and press the tape or sealant firmly into place. Products such as roofing butyl tape or emergency waterproof sealant are available from most builders' merchants and DIY stores, and they can be effective stopgaps in dry conditions.
3. Use a Tarpaulin
If the leak is significant and you can safely access the exterior of the roof (or have a professional do so), a heavy-duty waterproof tarpaulin can be laid over the affected area and secured with weighted battens or rope. This is a common temporary measure used after storm damage and can protect your home until a full repair is carried out.
4. Replace a Broken Tile (If Safe to Do So)
If a single broken or displaced tile is clearly visible and accessible, and you're confident working at height with the proper safety equipment, replacing it can be a straightforward job. Carefully lift the surrounding tiles, slide out the broken one, and slot in a replacement. However, if you're unsure at any point, leave it to a professional — a fall from height is a far more serious problem than a leaking roof.
How to Repair a Roof Leak Properly (Longer-Term DIY Fixes)
For minor issues that don't require full professional intervention, some homeowners with DIY confidence can carry out proper repairs. That said, all roof work should be approached with caution and with appropriate safety measures in place — a ladder secured at the base and top, non-slip footwear, and ideally a second person present.
Repointing Chimney Mortar
If crumbling mortar around a chimney stack is allowing water in, repointing is a relatively accessible repair. Use a cold chisel and hammer to remove the old mortar to a depth of around 15–20mm, brush away debris, dampen the joints, and apply fresh mortar mix. Smooth it off with a pointing tool and allow it to cure fully before exposing it to rain.
Re-sealing Flashing
Flashing is one of the most common sources of roof leaks. If the flashing around a chimney, skylight, or vent has simply lifted or lost its seal but is otherwise intact, you can re-bed it using flashing tape or lead-compatible sealant. If the flashing itself is cracked, corroded, or missing, it will need replacing — this is often best left to a professional as it requires cutting into the roof structure.
Replacing Roof Tiles or Slates
A cracked or slipped tile can often be replaced as a standalone repair. For interlocking concrete or clay tiles, lift the surrounding tiles with a slate ripper or tile lifter, remove the damaged tile, and fix the replacement in place. For natural slate, a slate ripper is used to cut the nail holding the old slate, and the new slate is fixed using a lead or copper clip.
If you find multiple damaged tiles in the same area, or if the timber battens beneath are also rotting, the issue likely goes beyond a simple replacement.
When a Temopary Fix Is Not enough
When to Call a Professional Roofer
While minor repairs are sometimes manageable as DIY projects, there are plenty of situations where calling a qualified roofer is the right — and safest — decision.
Call a roofer if:
- The leak is large, ongoing, or getting worse despite temporary fixes
- You’ve been unable to locate the source of the leak
- There is significant mould growth in your loft or on interior walls and ceilings
- The damage involves multiple tiles, large sections of felt, or structural timbers
- Any flashing needs replacing rather than resealing
- Your roof is flat — flat roof repairs typically require specialist materials and techniques
- Your home has an older roof (20+ years) that may need a broader assessment
- There is any sign of sagging in the roofline, which can indicate structural issues
- You’re not comfortable working at height — this is always a valid reason
A reputable roofer will provide a written quote, give you a clear explanation of what needs doing, and ideally offer a guarantee on their work. If your roof is under a builder’s warranty or your home insurance covers storm damage, check whether a professional inspection is required before making a claim.
Preventing Roof Leaks in the Future
Once your leak is sorted, it’s worth taking steps to reduce the risk of it happening again. An annual roof inspection — ideally in autumn before the winter weather sets in — can help you catch small problems before they become big ones. Keep gutters clear of debris, trim overhanging branches, and address any moss build-up early with an appropriate moss treatment.
Most roof leaks are preventable with a little regular attention. A small amount of maintenance now can save you a significant repair bill later.
If you’re in any doubt about the condition of your roof or the safety of carrying out work, always consult a qualified roofing contractor. Working at height carries real risks, and professional repairs are often more cost-effective in the long run than repeated DIY attempts.