What People Really Mean by “Felt Roofing Felt”
When customers talk to me about a “felt roofing felt” roof, they usually mean any flat roof that looks black and is finished with mineral chippings. In reality, there are several very different products that all get called “felt” – some are modern, flexible membranes, and some are the old brittle stuff you might remember from sheds.
In my 18 years on the roof around Brighton, Hove and Worthing, I’ve seen perfectly good flat roofs ripped off just because they were called “felt”, and I’ve seen people try to save old, cracked layers that should have been replaced years earlier. So in this article, I want to clear up what felt roofing felt actually is, what types exist, and what I personally use when I’m building or upgrading a flat roof.
The 3 Main Types of “Felt” You’ll Hear About
If you ask me on-site what “felt” I’m using, I’ll usually break it down into three simple categories:
1. Old-Style Pour-and-Roll Roofing Felt
This is what many people still imagine when they think of felt: thin rolls of material laid out on hot bitumen and then covered in chippings.
- Strengths: Cheap, simple, used to be the standard everywhere.
- Weaknesses: Becomes brittle, cracks with movement, doesn’t like standing water, short overall lifespan compared with modern systems.
If your garage or extension was done 20–30 years ago, you probably have this kind of felt on your roof now.
2. Modern SBS Torch-On Felt Systems
This is what I normally mean when I talk about felt roofs on homes in Sussex. SBS (styrene-butadiene-styrene) is a rubber-modified bitumen that stays flexible for much longer. It’s usually installed in layers using a gas torch.
- Strengths: Flexible, durable, suited to our mixed Sussex weather, works well on garages, extensions, dormers and bay windows.
- Weaknesses: Needs a skilled installer – bad torching equals future leaks.
If you’re looking at a complete replacement on a lived-in property, this is usually the system I recommend and install. If you want a good idea of price, have a look at my flat roof felt cost and service page where you can also use my calculator for an instant estimate.
3. Breathable Felt Underlay for Pitched Roofs
Here’s where things get confusing. On pitched roofs, I also use the word “felt” when I talk about the breathable membrane that sits under tiles or slates. That’s a totally different product and job.
- Job: Stops wind-driven rain, helps manage condensation, adds a second layer of defence under your tiles.
- Where: Terraced, semi-detached and detached pitched roofs all over Brighton and Sussex.
If your issue is sagging or torn underfelt under tiles, that’s not a flat roof job at all – you’ll want to see how I handle roof batten and felt replacement on pitched roofs.
What I Actually Look for When Choosing Roofing Felt
Different roofs need different types of felt. When customers ask me what felt they should go for, I don’t just quote a brand name; I look at four key things.
1. Is the Roof Domestic or Just a Basic Outbuilding?
For a simple shed that you’re not too worried about, a basic felt can be enough. For anything over a living space – bedroom, kitchen, or lounge – I want a higher-spec SBS system with better fire performance and a proper multi-layer build-up.
2. How Much Foot Traffic Will the Roof Get?
If you’re going to be walking on the roof – to clean windows, check a satellite dish, or use it as a small terrace – I’ll choose a tougher mineral cap sheet or even suggest a different finish on top of the felt system so you’re not damaging the waterproofing every time you step on it.
3. How Exposed Is the Roof to Wind and Sun?
Roofs on sea-facing streets in Brighton and Hove see more UV and stronger winds than sheltered inner streets in Worthing. In my experience, that’s where the cheaper felt systems age and crack early. On very exposed roofs I’ll always push for better-quality membranes and stronger fixings at the edges.
4. What Is the Underlay Condition?
If the deck underneath is rotten, uneven or mismatched, I’ll fix that first. Good felt on a bad deck is wasted money. If you want me to have a proper look rather than guess from the ground, you can book a free roof inspection so I can check the structure and advise you properly.
How I Build a Proper Torch-On Felt Roof (Step by Step)
People are often surprised how many stages go into what they thought was “just some roofing felt”. Here’s how I actually build a new felt flat roof when I’m doing it properly.
1. Strip Back and Inspect the Deck
I start by removing old felt, nails, loose chippings and debris. Then I check the decking boards. Any rotten or soft boards get replaced, not patched. If the joists are suspect, I’ll show you photos through my client portal so you can see exactly what I can see, and I’ll price any structural works separately so there are no surprises.
2. Sort the Falls and Drainage
Flat roofs should never be truly flat. I create or improve falls so water actually runs to a gutter or outlet. If water is currently pooling, I’ll explain your options – reboarding, tapered insulation, or local adjustments – and give you the pros and cons of each before I start laying any felt.
3. Fit the Underlay Felt
This first layer is your safety net. I install an underlay felt that’s either nailed (on timber decks) or fully torched down, depending on the spec. I make sure it’s properly lapped and tight around all edges and penetrations.
4. Install the Main Torch-On Cap Sheet
This is the visible top layer – often a mineral-finished SBS felt. I carefully torch it, working steadily so I don’t overheat the felt or scorch walls and fascias. The overlaps, corners and upstands are the critical parts; that’s where poor workmanship on many roofs causes future leaks.
5. Detail Work: Upstands, Parapets and Flashings
On many Sussex properties, especially terraces, you’ll have parapet walls or shared firewalls. These need felt taken up and over, or correctly dressed into lead flashing. If your property has exposed walls that are letting in damp, I may recommend felt capping on firewalls and parapets to protect them properly.
6. Edging and Finishing
Finally, I fit drip edges and trims so water runs off cleanly into the gutter instead of creeping back into the deck. At the end I walk you through the whole roof, show you photos from during the work, and explain what I’ve used where and why.
Where Felt Roofing Felt Works Best on a Home
Felt isn’t just for big flat roofs. In my day-to-day work across Brighton and Hove I use felt systems on all sorts of smaller areas that cause big headaches when they leak.
Garage Roofs
Most of the tired, patched up flat roofs I see are on garages. Many have had layer upon layer of felt thrown over the top, with no thought given to the decking or drainage. If you want straight talk on what it costs to do a garage roof properly, you can play with my garage flat roof cost calculator to get an instant ballpark figure.
Rear Extensions
Kitchen and lounge extensions are ideal for modern felt systems, especially where you’ve got limited access or neighbouring properties close by. When I’m doing a rear extension roof, I pay a lot of attention to how the felt meets the house wall and any existing rooflines, because that’s where leaks sneak in if someone rushes the details.
Small Roofs: Bays, Porches and Dormers
Little flat roofs can be the most annoying when they drip over a front door or into a bedroom. Felt is a solid choice for bay windows, porches and dormers because it can be neatly formed around awkward shapes and edges. I match the colour and detailing to suit the front of your house rather than leaving it looking like a quick patch job.
Common Myths About Felt Roofing Felt
“Felt Roofs Only Last 5–10 Years”
In my experience, the old pour-and-roll jobs often did have short lives, especially when they were thrown onto poor decking. But a well-installed modern SBS felt system, on a solid deck with sensible drainage, can easily last much longer. The key is the whole build-up, not just the material name.
“Felt Is Always the Cheapest Option”
Not necessarily. Basic felt can be cheap to install, but if it fails early or needs constant patching, it stops being cheap in real terms. When I price a job, I tell you straight what makes sense for that roof, not just what gives the lowest headline number.
“All Roofing Felt Is Basically the Same”
Definitely not. I’ve seen people try to save money by buying bargain felt from DIY stores and asking someone to torch it on. The difference in flexibility, fire rating and lifespan between that and a proper roofing-grade SBS system is huge. I choose products I’m happy to put my name to, because if it fails, I’ll be the one back on your roof explaining it.
How I Work Differently When You Ask Me to Replace Your Felt Roof
The roofing trade has a bad reputation for vague quotes and disappearing once the money is paid. I run things differently, and I build that into every felt roofing project I take on in Sussex.
Instant Online Estimates
You shouldn’t have to wait a week just to know if a new felt roof is even in your budget. That’s why I’ve built online tools where you can get a realistic instant estimate for typical flat roofs, garages and extensions before you even pick up the phone.
Fixed-Price Quotes After a Site Visit
If the estimate looks sensible to you, I’ll come out, inspect the roof properly, and then give you a fixed-price quote. That quote includes everything we’ve agreed – materials, labour, waste removal – so you know where you stand before I start.
Total Transparency Through the Client Portal
Once the job is booked in, you get access to my secure client portal. There you can:
- See the schedule and agreed dates.
- View daily photo updates from your roof as I work.
- Download your invoices and any warranties safely.
If you’re at work or away while I’m on the roof, you’ll still see exactly what’s happening every day.
When to Repair Felt and When to Replace It
If you ask me on-site whether a felt roof can be repaired, I’ll always try to save you money where it makes sense. But there are some clear red flags where I’ll advise a full replacement instead of another patch.
Signs a Repair Might Be Enough
- One small split or hole in an otherwise sound roof.
- Localised damage from something like a slipped tile or heavy object.
- Flashings that have lifted but the main felt field is still flexible.
Signs You’re Better Off Replacing the Roof
- Cracking all over the surface when you bend or press the felt.
- Multiple historical patches and repairs.
- Persistent ponding water in several areas.
- Soft spots in the deck when walked on.
The best way to judge it is for me to get up there, lift what I need to, and show you clear photos. Then you can make a decision with all the facts in front of you instead of guessing from the garden.
What to Do If Your Felt Roof Is Leaking Right Now
If your felt roof has suddenly started leaking – especially over a bedroom, kitchen or hallway – don’t ignore it and hope it dries out. The sooner I can see it, the better the chance of saving the deck and keeping the cost down.
For serious leaks and visible water coming through ceilings, use my emergency roof leak booking page so I can prioritise you properly. I’ll always be upfront about what I can realistically do in bad weather and what might need a temporary fix first.
My Honest Advice If You’re Unsure About Felt Roofing Felt
If you’re staring at a quote that just says “felt roof” and you’re not sure what you’re actually getting, here is my honest advice:
- Ask exactly what type of felt is being used (brand, thickness, number of layers).
- Ask how the falls and drainage will be improved, not just how the top layer will look.
- Ask what happens if rotten decking is found midway through the job – is it included or extra?
If you want a second opinion, I’m always happy to come out, look over your existing roof and talk you through the options in plain English. Once you understand what “felt roofing felt” really means in your situation, the right choice normally becomes obvious.