Fixing a Felt Roof: What I Tell Customers Before They Spend a Penny

When customers ask me about fixing a felt roof, they usually want one of three things:

  • Stop a leak quickly before it ruins ceilings and electrics
  • Patch a few cracks or blisters to squeeze a couple more years out of it
  • Honest advice on whether it’s still worth repairing at all

In my 18 years on the roof around Brighton, Hove and Worthing, I’ve seen felt roofs in every state you can imagine – from a tiny split around a pipe to garages with four different patch jobs layered like a lasagne. Here’s my honest breakdown of how I look at fixing a felt roof, what you can realistically DIY, and when you’re just throwing good money after bad.

First Step: Work Out What Kind of Felt Roof You’ve Actually Got

Before I even think about how to fix a felt roof, I identify what I’m standing on. The way I repair it depends a lot on the age and type of felt:

1. Old mineral felt or chipping-covered roofs

These are usually older roofs with either a rough mineral finish or covered in small stones (chippings). Signs I look for:

  • Lots of fine cracks when it’s dry
  • Loose or bald patches where stones have moved or washed away
  • Ridges and ripples where the felt has moved

These can be patched, but if the surface is crazed all over, repair is usually only a short-term fix.

2. Modern SBS torch-on felt systems

This is what I install on most flat roofs now. It’s much tougher and more flexible. When it fails, it’s usually in specific weak spots:

  • At the edges where it meets the wall or gutter
  • Around roof lights and pipes
  • On seams where two rolls meet

These systems respond well to proper repairs, as long as the base layers are still sound.

3. Cold-applied felt and DIY roll roofing

These are the ones often bought from DIY shops and stuck down with cold adhesive. They typically fail:

  • Where the adhesive was thin or patchy
  • Because of poor overlaps
  • At upstands (where the roof goes up a wall) that weren’t detailed properly

I’ll be straight with you – I can usually repair them, but they rarely behave as nicely as a properly installed torch-on system.

Find the Leak First – Then Decide How to Fix the Felt

Most people call me because water is already coming through. The tricky part with felt roofs is that:

  • Water often travels before it shows up inside
  • The visible drip can be several metres from the actual entry point

When I’m tracing a leak, here’s how I approach it:

  • Check the obvious weak points first – seams, edges, corners, pipes, roof lights
  • Look for ponding – standing water often finds its way through even a tiny defect
  • Press blisters gently – if water squelches underneath, that area needs stripping and proper repair
  • Look under the roof if possible – in a garage or loft, I check for dark stains, rot or damp joists

If the leak is urgent and you need it stopped fast, you can book my priority emergency roof leak repair and I’ll focus on stabilising the problem first, then talk you through longer-term options.

Common Felt Roof Problems – And How I Actually Fix Them

1. Small cuts, nail pops and localised splits

What it looks like: Little slits in the felt, often near fixings or seams. Sometimes you’ll see a nail head pushing through.

How I fix it properly:

  • Clean and dry the area thoroughly – no dust, no algae, no loose mineral
  • Cut a patch of felt that extends well beyond the damage (at least 100mm each side)
  • Round off the corners of the patch so they don’t lift later
  • Use torch-on or adhesive (depending on the system) to fully bond the patch
  • Check the surrounding area for other stresses – if one nail has popped, others may follow

DIY-wise, this is the sort of thing a confident homeowner sometimes has a go at. My honest advice? If it’s your main living space underneath and you care about the finish, get it done professionally. A bad patch can trap water and cause a bigger problem.

2. Blisters and bubbles in the felt

What it looks like: Raised humps or bubbles. They might be soft (air) or squelchy (water).

What I do on site:

  • If it’s a small, dry blister away from seams, I may leave it if the membrane is sound
  • If it’s large or holds water, I cut it open, dry the area out and inspect the layers below
  • If the base layer is still bonded, I re-bond and patch with new felt
  • If the base is shot, that section needs stripping back and rebuilding

If you ask me, any blister that holds water is a warning sign. It may not be leaking yet, but it’s heading that way.

3. Failed joints and overlaps

What it looks like: Dark lines where seams have opened, visible gaps, or edges you can lift with your fingers.

My approach:

  • Lift back any loose felt carefully
  • Clean out dirt, old adhesive and loose mineral
  • Re-bond with appropriate adhesive or heat (for torch-on)
  • Add an additional cover strip across the joint if it’s in a critical area or heavily weathered

In my experience, if lots of seams are failing across a roof, it usually means the whole covering is at the end of its life.

4. Edge details and perished drip trims

What it looks like: Water running behind the gutter, rotten fascia boards, felt curling away from the edge.

How I fix it:

  • Strip back the loose edge felt
  • Replace or repair the timber or fascia if it’s rotten
  • Install new drip trims or form a proper metal edge
  • Re-lay or patch the felt with a clean, secure edge detail

On a lot of garage and porch roofs, customers ask me to sort this at the same time as upgrading the felt. If you’re curious what that might cost, you can use my garage flat roof cost calculator for a quick guide price.

5. Problems around walls, parapets and upstands

What it looks like: Damp patches inside where the flat roof meets a wall, cracks where the felt turns up, or surface moss on the verticals.

My repair method usually involves:

  • Stripping back the failed felt from the wall or upstand
  • Checking for loose render, blown bricks or missing pointing
  • Installing new felt upstands with the correct height and fixings
  • Finishing with proper capping or lead, depending on the situation

For parapets and party walls, I often recommend a more robust solution. That’s why I offer dedicated firewall and parapet felt capping – it massively reduces damp problems along those junctions.

When a Felt Roof Repair Is Worth It – And When It’s Not

Here’s the part most people actually want to know. I’ll keep it simple and tell you exactly how I look at it on site.

Situations where a repair usually makes sense

  • The leak is localised – one clear defect, rest of the roof looks sound
  • The felt is under 10–12 years old – especially if it’s a decent torch-on system
  • The decking underneath is solid – no bounce, no rot
  • The roof isn’t heavily ponding – a couple of shallow puddles are fine, a shallow pond is not

In those cases, a well-done repair can give you several more years without trouble.

Red flags that tell me repair is just delaying the inevitable

  • Widespread crazing and cracking across the surface
  • Multiple old patches already in place – especially if they’re failing too
  • Soft, spongy feel underfoot – often means rotten boards underneath
  • Severe ponding in the middle of the roof after rain
  • Visible sagging between joists when viewed from the side

In those situations, I’ll tell you straight: you’ll keep calling people out every winter, or you can bite the bullet once and have it done properly.

If you want a clear, fixed-price option to compare against constant repairs, have a look at my flat roof replacement and repair service. It covers modern SBS torch-on felt, which is what I use on most domestic flat roofs now.

DIY Felt Roof Fixes: What You Can Try – And What to Avoid

People sometimes apologise when I arrive and see that they’ve tried to fix it themselves first. You don’t need to. I understand why you’d have a go, but here’s my honest take on DIY repairs.

Jobs a careful DIYer might reasonably attempt

  • Temporary patching of a small, obvious split using a felt repair kit
  • Cleaning and re-sealing a slightly lifted joint with cold-applied mastic
  • Clearing blockages around outlets and gutters that cause ponding

If you do try a DIY fix, keep it small-scale and temporary. Don’t layer half a bucket of goo over the problem area. Thick, messy coatings can trap water and make a professional repair more complicated later.

Jobs I strongly recommend leaving to a roofer

  • Anything involving a blowtorch – it only takes a second to scorch the felt or set the decking on fire
  • Repairs near gas flues, electrics or roof lights
  • Working at height without proper access or edge protection
  • Strip and re-lay of larger sections – getting falls, overlaps and details right is critical

In my 18 years on the roof, I’ve seen more damage caused by over-enthusiastic DIY repairs than by the original fault. Sometimes the best DIY choice is to stop, take photos, and let me have a look.

Special Cases: Garages, Porches, Extensions and Bay Roofs

Not all felt roofs are equal. Some areas of the house are a bit more forgiving than others.

Garages and outbuildings

These are where I’m most likely to recommend a last-ditch repair if you’re trying to squeeze another year or two out before replacing. As long as the structure is safe and you understand it’s not a forever fix, I’m happy to patch sensibly.

Rear extensions and living spaces

On kitchen or lounge extensions, my tolerance for “cheap and cheerful” repairs is much lower. The risk to insulation, plaster, electrics and cabinets is much higher.

If you’ve got a felted rear extension that keeps giving you trouble, it may be worth looking at a more thorough upgrade. That’s exactly what I aim for with my rear extension flat roof repair and replacement service – sort the leaks, improve insulation where possible, and tidy up all the tricky details around doors, windows and lanterns.

Bay window and porch roofs

These are often the most visible felt roofs on a house, and they’re usually installed with poor details originally. Fixing them properly often involves:

  • Improving the way they drain
  • Upgrading the edge trims
  • Dealing with the connection to the main wall and any existing leadwork

A neat repair or replacement here can make a big difference to the look of the front of your house.

How I Approach Fixing Your Felt Roof in Practice

If you contact me about a felt roof problem, here’s what actually happens:

1. I ask you a few key questions

  • How old is the roof, roughly?
  • Where is the leak showing inside?
  • Is it getting worse, or just appeared suddenly?
  • What type of room is underneath – garage, kitchen, bedroom?

2. I come out and inspect the roof

I don’t rush this. I’ll walk the roof, check the critical junctions, and usually take photos to show you exactly what I’m seeing. I’m looking to answer one question clearly: Is this roof genuinely worth repairing, or are you better off replacing it?

3. I give you clear options

  • Short-term repair – what I can do now to stop the leak and how long I expect it to last
  • Longer-term solution – what a proper refurbishment or replacement would involve
  • Costs and disruption – all in, with no hidden extras

If you want a full health check on your felt roof before making a decision, you can book a free roof inspection and I’ll walk you through the options in person.

My Honest Advice on Fixing a Felt Roof

If you ask me, here’s the simple way to think about it:

  • If the roof is generally solid and the problem is local – a proper repair is usually a smart move.
  • If the roof is tired all over, and you’re fixing a new issue every year – stop wasting money on patches.
  • If the room underneath is important (kitchen, bedroom, lounge) – err on the side of a more robust solution.
  • If it’s a garage or shed and you just need it to limp on – I can usually find a sensible middle ground.

I don’t believe in scaring people into full roof replacements when a straightforward repair will do the job. But I also won’t tell you a worn-out felt roof is fine just so I can sell you another patch next winter. When I stand on your roof, I treat it like it’s my own house – that’s the standard I work to.

If you’re unsure whether your felt roof is fixable or finished, take a few clear photos and get in touch. Between a quick chat and a closer look on site, I’ll give you a straight answer and a fixed price so you can decide what makes sense for you and your home.