Your roof is leaking. You climb into the loft, torch in hand, and spot the culprit, torn or sagging roof felt. The question hits: can you fix it from the inside?
It seems like a simple solution. No ladders, no roofers, no costly scaffolding. But is it really that easy?
Let’s dive into what’s possible, what’s not, and what to watch out for when repairing roof felt from inside the loft.
What Is Roof Felt and Why Does It Matter?
Roof felt, also called underlay, is the membrane that sits beneath your roof tiles or slates. It acts as a secondary barrier against water, wind, and dust.
Think of it as a backup plan:
If tiles crack or shift, the felt stops water getting into your loft.
If wind lifts tiles, the felt keeps draughts and rain out.
It helps prevent damp and mould inside your roof space.
Over time, this felt can sag, rip, or degrade, especially in older homes where bitumen-based felt was common. Once it’s damaged, water gets in and small leaks can turn into big problems fast.
Can You Actually Repair Roof Felt from Inside?
The short answer: yes, but only in some situations.
It depends on a few key factors:
Extent of the damage – is it a small tear or widespread rot?
Access and visibility – can you safely reach and see the damaged area?
Roof design – does the felt sit flat or tight against the rafters?
When It Might Work:
You might be able to patch roof felt from inside the loft if:
The damage is small and localised (like a rip or minor sagging).
You can clearly see the hole from inside.
The area is dry enough to work on safely.
The roof structure allows you to reach the felt without removing insulation or squeezing into tight spaces.
A practical example:
A semi-detached house built in the 1980s had a small tear in the felt near the eaves. The homeowner noticed a damp patch on the bedroom ceiling and traced it back to the loft. With good access and dry weather, they patched it from inside using roofing tape and it held.
When It Won’t Work:
There are clear limits. You can’t do an inside repair if:
The felt is perishing across large areas.
Water has soaked the insulation or timbers.
The tear is right under roof battens or inaccessible spots.
It’s a temporary fix for a structural issue, like failing tiles or rotting rafters.
Trying to repair from inside in these cases won’t stop the leak and might trap moisture inside the roof space, making the problem worse.
How to Repair Roof Felt from Inside the Loft
If you’ve assessed the situation and think an internal patch is possible, follow this guide.
Tools and Materials You’ll Need:
Torch or work light
Safety goggles and gloves
Roofing tape or self-adhesive felt patches
A stable loft board or platform to work on
Utility knife or scissors
Measuring tape
Optional: Spray adhesive or roofing sealant for extra hold.
Step-by-Step Process:
Safety First
Ensure the area is dry. Never work in the loft during wet or icy weather. Use stable boards and avoid stepping between joists.Locate and Inspect the Damage
Look for rips, holes, or sagging felt. Check for signs of water damage on the woodwork or insulation nearby.Dry and Clean the Area
Use a cloth to wipe down the felt. It must be clean and dry for the patch to stick.Cut Your Patch
Measure the damaged area. Cut your patch at least 5-10 cm larger on all sides to fully cover the hole.Apply the Patch
Stick it firmly over the tear. Press out any air bubbles. For extra hold, seal the edges with spray adhesive or tape over them with overlapping strips.Monitor Over Time
Recheck the repair during or after rain to see if water is still getting in. Watch for fresh damp patches or mould growth.
What About Long-Term Reliability?
Here’s the honest truth: internal repairs are almost always temporary.
Why? Because:
You’re not fixing the underlying cause (like broken tiles).
The patch is only bonded from one side.
Moisture may already be present behind the felt.
You might stop a small leak for a while, but don’t expect it to last through heavy storms or over multiple seasons.
A survey by the National Federation of Roofing Contractors (NFRC) showed that 72% of roof leaks were due to issues above the underlay missing or cracked tiles, failing flashing, or poor ventilation.
The internal felt is just part of a bigger system. Fixing one layer without addressing the rest is like patching a tyre with tape, it might get you home, but it won’t last the journey.
What Are the Alternatives?
If the damage is too serious for an internal fix, consider these options.
1. External Patch (Under a Tile)
If you can safely access the area from outside:
Lift the tile(s) above the damage.
Remove any rotten felt.
Slide a new patch under the battens.
Secure with nails or staples and seal with tape.
This method creates a more watertight seal and it’s repairable without replacing the whole roof.
2. Felt Replacement in Local Sections
Some roofers can replace strips of felt along the eaves or verge without redoing the whole roof. This involves:
Removing several rows of tiles.
Cutting away damaged felt.
Installing new breathable membrane.
Replacing the battens and tiles.
More invasive but more durable.
3. Full Roof Underlay Replacement
If your felt is over 30 years old, brittle, or failing in multiple places, a full re-felt might be needed. It’s not cheap, but it protects your home for decades.
The average cost of a full roof felt replacement in the UK ranges from £3,000 to £7,000 depending on size and access.
How to Know When It’s Time to Call a Professional
Ask yourself:
Is the leak getting worse, even after a patch?
Is there mould or rot on roof timbers?
Are multiple sections of felt damaged?
Do you see daylight through the roof felt?
If you answered yes to any of these, it’s time to get expert help. A qualified roofer can assess the whole structure and recommend the most cost-effective solution.
Final Thoughts: Should You Attempt It?
Let’s bring it all together with one last question:
Do you want to stop a drip or solve the problem?
If the damage is small, easy to reach, and caused by minor wear, a DIY patch from inside might buy you time.
But if your roof is older, or the damage keeps coming back, don’t waste energy on band-aid fixes. A proper repair, done from above, is safer, stronger, and ultimately cheaper in the long run.
Your roof protects everything beneath it.
Sometimes, the best fix isn’t the easiest, but it’s the one that works.
