If you’re reading this article the chances are that you’ve a flat roofing issue on your mind. Your might be planning an extension, home garden project or simply looking to replace an older flat roof. There’s a lot of choice out there and deciding on the best option for you is a balancing act between cost, durability and flexibility.

After a few ‘flat roof’ related Google searches you’ll find a multitude of flat roof materials are available, offering a range of attractive features and coming with a range of price tags. Some are DIY-able, others you’d be better hiring a flat roofing expert. We say flat roofing expert because general roofers might not have the specialist knowledge required to fit a flat roof correctly. This comes with skill and experience so you want to chose your roofing contractor carefully. It you want to reap the benefits of a flat roof it must be fitted properly, otherwise you leave yourself open to a whole host of issues.

In this article we hope to explain a few of the main types of flat roof & offer a little help in choosing which type of flat roof might be best for your needs.

But first, in case you’re still on the fence between getting a tiled or slated pitched roof and a flat roof let us explain why we think flat roofs are best.

The main benefit of a flat roof is its low maintenance and high durability. Once a flat roof is installed you can pretty much leave it alone and it’ll hold fast whatever mother nature throws at it (in the UK at least).

Flat roofs are generally cheaper than tiled/slate roofs- taking installation, maintenance and repairs costs into account, flat roofs are versatile- you can have a roof garden, a balcony, or simply easy access to your first floor windows and gutters and they’re quick to install. If you want to talk to the experts in flat roofing, Northern Roofing Solutions Ltd, an authority on types of flat roofing in Liverpool would be happy to take your call & help you with your flat roofing question.

So, the next question to answer is- which material will be best for your flat roof?

Types of flat roofing

Felt & Asphalt

Felt flat roofing

Also Known As: Felt Paper, Asphalt Felt Paper (similar to tar paper)

Pros:

Lifespan – Most guarantees are 10 Years, my contractor guarantees 20 years. I think a well installed Torch-on felt roof could well last up to 30 years if looked after and treated well.

Cost – The cheapest option on the table here, see – Flat roof costs

Damage resistance – Foot traffic in hot weather may scuff the surface of a mineral finish; this can lead to U.V. damage by sunlight. Window cleaners also put step ladders and ladders on them in hot weather which could damage the surface.

Repair – Easily repaired but patches on top can look messy, the plain cap sheet with solar reflective paint is the most repairable and popular in unseen and industrial settings for this reason.

Appearance – Beauty is in the eye of the beholder, but I think a mineral finish is pretty to look at, I like brown and purple.

Installation issues or concerns – Make sure that any contractor has full insurance to work with hot flame, mine carries £10,000,000 liability – never attempt a DIY installation.

Flexibility – Modern roofing felt has good expansion and contraction properties.

Vapour transmission – Roofs are often called on to breathe. Thanks to the vapour layer a felt roof will do this. I would however personally never rely on a roof covering alone, especially if you have condensation issues. This should be dealt with in house or during roof construction.

Cons: Degrades quicker than other types of flat roofs, limited aesthetics, exposure to the sun can reduce its lifespan

There are a range of types of felt roofs so lets start with the earliest one we’re going to cover- Mastic asphelt. Asphalt is more commonly known to be used in road and pavement construction but its also a useful roofing material. This material was used in the early 20th century as it worked well on buildings made with dense, bonded material due to their limited movement. Mastic felt isn’t very flexible, movement, especially in cold weather when it can become brittle, can cause it to crack.

In the 60s & 70s people started to use Mineral Felt as it was an inexpensive and quicker alternative. It consisted of pouring and rolling hot bitumen over the roof and was sealed at edges and joints. It had a life span of around 10 years which would be reduced if it was used for access to windows and gutters. Its bad reputation is partly due to poor workmanship. As many roofers were paid per job (piece work) and a quick job meant more money and so jobs were often rushed.

Next came Torch on Felt roofing which came in the form of a kind carpet which you would torch on the underside to make it sticky to it’d stick to the substrate (the underlying timber).

Felt is commonly found on garage and shed roofs, they’re quick to install, are lightweight and the cheapest option for flat roofing projects.

However, they have a short lifespan of around 10 years and are prone to weather damage, becoming soft and pliable in hot weather and brittle in cold weather. It can still be a good solution for small projects though, especially garden buildings, tool sheds and garages.

GRP roofing

GRP flat roofing

Also know as: fibreglass roofing and glass reinforced plastic.

Pros:

Lifespan – Most guarantees are 25 Years, and there will be no problem for this type of roof to achieve this if properly installed. I have personally seen fibreglass roofs that are 30 years old with no visible signs of wear apart from slight UV fading of the top coat ( colour ).

Cost – Normally the most expensive option out of the three due to high material costs as re-boarding is normally required with OSB3. See – Flat roof costs

Damage resistance and repair – Incredibly resistant to most forms of damage, its extremely tough once cured. Repairs are very easy and can be almost invisible.

Appearance – For my money the prettiest roof money can buy if installed sympathetically. It can look a bit new and plastic for the first 6 months to a year before the wax finish dulls on the topcoat colour. Lead flashings nearly always look better than the GRP flashings in my opinion.

Installation issues or concerns – Make sure that any installer knows what he’s doing, skimping on resin or topcoat can cause pinholes and expansion guidelines must be followed, especially on larger roofs.

Flexibility – Whilst new specialised roofing resins are flexible they are not as flexible as felt, or certainly not as flexible as EPDM. Roofs over 50 to 100m2 need serious thought and expansion planning before undertaking.

Vapour transmission – Fibreglass roofs do not breathe well, a bit like glued EPDM, so if condensation is a problem in your property this may have to be designed into the roof construction or elsewhere in the house.

Cons: Needs dry weather to install (might be a struggle in the UK!), expensive, inflexible

GRP, or Glass Reinforced Plastic, is a very popular flat roofing solution for many domestic jobs as well as small to medium sized commercial roofing projects.

Fibreglass flat roofing is very strong and durable, it comes with a guaranteed warranty of 20 years but its life expectancy is in excess of 40 years if properly maintained. GRP roofs are weatherproof and so are at little risk of leaking or developing frost damage.

Their durability also makes them very good for footfall, which can be useful if you plan to use your flat roof for access to first floor windows and gutters.

To give you an idea of how tough GRP they’re also used for the hulls of some boats which can withstand years of rough sea conditions.

If you want an elegant looking flat roof GRP is a great options. Grey is the most commonly used colour and gives your new roof a lead-look. You can also get it in a range of other colours but you’ll pay extra for this option. You can also get a range accessories for GRP roofs such as trim, tilt fillet, outlets and cappings which can give the roof a tidy and elegant finish.

So GRP is durable, long lasting and very tough. The main downside is that they need to be installed in dry conditions and so summer time is best for this kind of job. It’s also pretty inflexible and so you need to build on a dense and bonded structure to limit movement. It costs more than felt and rubber roofing but it’s worth the extra money if you can stretch to it.

Rubber roofing

Rubber roofing example

Also know as: EPDM, ethylene propylene diene monomer, waterproof felt, single play membrane roofing

Pros:

Lifespan – Some guarantee up to 50 years. This seems to be an immensely variable figure from installer to installer, and I question whether they plan to be in business or honour a guarantee with a 50 year time frame. From what I’ve seen so far a well installed EPDM roof should last 30 years upwards. I’m happy to guarantee mine for 25 years from what I have seen so far on ageing UK installations.

Cost – Very competitive, expect to pay 20%-30% more for a nice example in relation to a torch on roof. See – Flat roof costs

Damage resistance – Very tough in most situations and foot traffic, always place something to spread the weight underneath a ladder though. And do not throw food on top of the roof for the birds, as I have seen a roof ruined by seagulls pecking it because they fight over scraps. Can be repaired easily, but can look a bit obvious, as it normally involves gluing on patches a bit like an inner tube repair.

Appearance – For me this is a downfall, personally I’m not keen on the black, black/grey look of the roof, especially if it is to be overlooked from a window. That said a good neat installation helps.

Installation issues – Unfortunately the perceived easy D.I.Y. fitting of this roof has brought the cowboys out to play, some are simply horrible to look at, wrinkly, saggy and without correct edging strips at drips. Also be aware of roof details, although a roof can be seam free, corners, pipes and complicated drips will mean joins, and these should be done carefully and with thought by either a Trade or a DIY installer.

Flexibility – You will simply not beat a rubber roof for expansion and contraction, if you have a large roof where this is a real concern, EPDM is for you.

Vapour transmission – This is dependent on layers that may be underneath, but in normal glued down install it will breathe less than a torch on felt roof. If condensation is a problem this may have to be designed into the roof construction or elsewhere in the house.

Cons: Easily damaged/vandalised, risk of joint glue contamination, expensive

Rubber roofing is a type of single ply membrane roofing, we know we’ve covered single ply membranes in the next section below, but rubber roofing is particularly popular and so we though we’d give it special attention. In short single ply membrane roofing is a single layer of water proof roofing material. They’re lightweight, quickly installed and cost effective roofing systems which are produced to very strict manufacturing quality control requirements making them increasingly popular in both domestic and commercial roofing.

Rubber roofs are very durable and long last coming with a 20 year warranty and a life expectancy of over 25 years. EPDM comes in a variety of grades and the higher the grade the better quality the material. It’s glued directly to the timber roof structure and joints are glued together making this type of roof very waterproof when it’s in good condition. It comes in a small range of colours, grey shades being the most popular and so its also the cheapest.

There is the risk of contamination of the glue used to bond joints with EPDM roofs. If they become contaminated with dust or water it can reduce their effectiveness and can lead to roof failure.

This material cannot be recycled it can however be reused if it’s laid loose and mechanically fixed to the underlying roof structure. Due to it’s small disadvantages EPDM is the cheapest single ply membrane material. Making is a very viable option for roofing jobs for the home and garden.

Single Ply Membrane

Single ply roofing material

Also Known As: Upside-down roofs, protected membrane roofs

Pros: lightweight, cost effective, flexible, durable, weather proof, mostly simple to install

Cons: usually not recyclable, often requires very clean installation,

Single ply membrane roofing is gradually becoming a very popular roofing solution for homes, gardens and businesses. It’s main benefits come from it’s long-lasting durability, ease of installation and cost effectiveness. There are a range of single ply materials available coming in a range of colours and with a variety of joining or fixing methods making it a viable choice for most budgets.

Single ply membranes are ideal for all roofing projects including new builds, refurbishments, flat, pitched or curved roofs, garages, extensions, conservatories and dorma conversions.

PVC. If you like simplicity and choice PVC is a great option for you. It can’t however be laid over bitumen unless an isolating layer is installed first so if you’re replacing a felt garage roof you’ll need to take this into consideration. It also contains plasticiser and chlorine making is a bad choice if you want to be environmentally friendly.

TPO (Thermoplastic polyolefin) is for those of you who want to do their bit for the environment without paying a hefty price. it can be partially recycled and doesn’t contain plasticisers. The range of colour are limited to greys and life expectancy is a little lower but its still a very good option.

TPE (Thermoplastic Polyolefin Elastomer) is the next step up in environmentally friendliness. It’s 100% recyclable with much simpler installation, quick and easy to repair, even small holes without the need for patches. You’ll pay a little more for this type of membrane though, but at least you can feel good about it.

PIB (Polylso Butylene) is the most long lasting single ply flat roofing solution, still going strong after 50 years! It’s so environmentally friendly that it’s full life cycle, from manufacture to recycling, has a very limited effect on the environment. What’s more its easy to install, durable and very cost effective.

To bring the main pros and cons of each flat roofing material we’ve covered in this article we’ve created a venn diagram. It covers durability, flexibility and cost effectiveness. We hope it helps display how the options pan out.

 

For more information about the best types of flat roofing for the Salford and Manchester areas please click on the link,