What product for your flat roof?

The following list is not exhaustive and many more systems and products are available. Also, each category can be broken down further.

For the purpose of this article we have chosen the most popular systems.

We have summarized into 7 categories below the most common flat roofing products and have chosen the flag ship manufacturers as examples in each. Click on the highlighted manufacturers to view BBA certificates, within each certificate we draw your attention to the durability section.

1. Bitumen based roofing

Tar and gravel, Bitumen or Modified Bitumen, Pour and roll felt roofs, Torch on felt roofs   (Anderson monarflex)

2. Rubber Roofing

EPDM   Carlisle Sureseal,  Rubberbond

3. Liquid Plastics

Decothane,  Scotchkote

4. Metal Roofing

Corrugated coated steel (Euroclad),   Aluminium standing seam (Kalzip), Lead, Zinc, Copper

5.  PVC - Single-Ply

SIKA Trocal/Sarnafil,   Icopal Monarplan

6.  TPO - Single-Ply

Polisystem uk,   Icopal Sureweld

7.  GRP

Topseal,   Flexiflow

Below we will take each in turn and give the pro's and con's

1.  Bitumen based roofing

Pro's

• Many roofing contractors to choose from hence may be able to get lower price.

• Good puncture resistance

Con's

• Outdated system

• No Approval system for contractors (anyone can install)

• Any Tar/Bituminous material is highly susceptible to cracking and becoming brittle.

• Damaged by the Suns UV light

• Dangerous to install

• Human error risk inherent in built-up systems

• Unusual for any manufacturer to offer more than a ten year guarantee.

2. Rubber Roofing

Pro's

• Fast Installation

• Cheap material to purchase

• Many installers to choose from

• Manufactured in a factory to strict quality control requirements that minimize the risk inherent in built-up systems

• No specialist equipment required for installation

Con's

• Although marketed as a selling point the fact this material is installed in very wide sheets is a big problem, while wider sheets can reduce the number of seams on a roof, long-term wind resistance is compromised in mechanically fastened applications.

• Due to the above, most rubber jobs will be glued down, with this system you’re totally reliant on the substrate that you’re adhering the rubber to, in order to hold the roof on. You’re not using fasteners, you’re just gluing the membrane to the substrate. If the plywood or insulation de-laminates, or the glue has been applied in damp conditions then you run the real risk of your roof being damaged or even coming off in high winds..

• No ponding water warranty.

• Easily punctured

• Poor fire rating

• Rubber roofs are very prone to leaks, as the seams are glued together and adhesive tends to break down within 5-7 years  (even in a roof that is installed in one complete sheet the material still has to be joined to the perimeter details).

• No approval system, there are too many contractors who will install rubber roofing products without proper knowledge and training

• Black is the only colour product comes in

• Must be an approved contractor with training to purchase and install this product hence a high level of skill and professionalism is achieved

• Easy detailing on roofs with many penetrations

• Guarantees of up to 20 years

• Roof inspection when job is complete by manufacturer before issuing guarantee.

• No laps or seams

• Comes in a 3 different colours

• Very difficult to install correctly in the Scottish climate and weather. Any water hitting material before fully installed would result in improper adhesion and may require a strip off and redo. Cannot be installed below 5 degrees C.

• Totally reliant on the substrate that you’re poring the liquid onto, in order to hold the roof on. If the plywood or insulation de-laminates then your roof could be damaged in high winds.

• Small holes in substrate can cause holes in product if not filled before installation.

• Hard for inspector to determine how well bonded to substrate the product is during inspection.

• Can be very expensive due to contractor having to factor in downtime due to weather.

• Human error risk inherent as in built-up systems.

• Very good commercial product

• Very hard wearing and puncture resistant

• Can be installed in bad weather

• Quick to install

• Manufactured in a factory to strict quality control requirements that minimize the risk inherent in built-up systems.

• Up to 25 year guarantees with some systems

• Various colour options

• Not a good product aesthetically for domestic jobs and planning issues often arise.

• Noisy when rain hits product which can be masked on commercial projects but is very apparent on domestic jobs

• Expensive for curved and detail applications

• Roof has to have a pitch of at least 5 degrees for installation as the sheets are not sealed at joints

• Must be an approved contractor with training to purchase and install this product hence a high level of skill and professionalism is achieved

• Manufactured in a factory to strict quality control requirements that minimize the risk inherent in built-up systems

• Resistant to weathering, chemical oxidation and UV radiation

• Very good fire rating.

• Manufactured with a glass fibre or polyester scrim to add support to prevent  tearing and stretching, allowing for mechanical fixing.

• Laps are hot air welded and become totally fused together and are then in essence the same continuous piece of material, in fact because the laps are thicker they are actually stronger than the rest of the material.

• Can be installed easily in the UK climate.

• Guaranteed up to 25 years with laps and ponding water covered

• Various colour options

• Ongoing inspection while installation is in progress and inspection when job is complete by manufacturer before issuing guarantee

• BBA certificate durability rating in excess of 30 years and working examples in excess of 40 years

• Fast installation

• Expensive product to purchase.

• Expensive equipment required to install.

• Must be an approved contractor with training to purchase and install this product hence a high level of skill and professionalism is achieved

• Manufactured in a factory to strict quality control requirements that minimize the risk inherent in built-up systems

• Resistant to weathering, chemical oxidation and UV radiation.

• Manufactured with a glass fibre or polyester scrim to add support to prevent  tearing and stretching, allowing for mechanical fixing.

• Laps are hot air welded and become totally fused together and are then in essence the same continuous piece of material, in fact because the laps are thicker they are actually stronger than the rest of the material.

• Can be easily installed in the UK climate.

• Ongoing inspection while installation is in progress and inspection when job is complete by manufacturer before issuing guarantee

• Fast installation

• Expensive product to purchase

• Many systems do not get inspected. When system does get inspected it is hard for the inspector to determine how well bonded to substrate the product is.

Modern roofing have experience in felt, GRP and rubber roofing (although we now mostly only repair these roofs) and are approved installers for Decothane, Kalzip, Euroclad, SIKA and Polisystem.

Because of the issues stated categories 1, 2 and 7 (BUR, Rubber roofing and GRP) are rarely installed on any commercial building today and Modern Roofing do not recommended to be installed on domestic projects. Serious consideration should be given to the contractor being used because these products can be purchased and installed by anyone.

Liquid plastics can be a very good product if the weather allows for proper installation but reliance on the integrity of the substrate causes concern, although concrete substrates can work very well.

Metal Roofing is a very good product for commercial projects and would be recommended on some projects by Modern Roofing.

TPO Single-Ply Membrane is a very good product for both domestic and commercial applications although does not have the track record of PVC. Not as aesthetically pleasing as PVC due to susceptibility to wrinkling in strong sunlight.

PVC Single-Ply Membrane is a very good product for both domestic and commercial applications although can be expensive if small volumes are bought for domestic jobs.

Modern roofing can reduce the cost of PVC material because the sheer volume of the product we purchase from our suppliers (over 30'000 square metres in year 2013 to 2014) has allowed us to negotiate a large discount which we pass on to our domestic and commercial customers. This has brought pricing in line with the other flat roofing products.

When deciding on purchasing a new flat roof ask yourself why most new roofs on public contracts like schools and hospitals and commercial projects like car show rooms and restaurants have either Metal Roofing or PVC Membrane roofs. Also, have a look at BBA rating and consider why the durability rating of PVC is 10 years longer than one of the best felting systems on the market (most of the time when you purchase a felt roof you will not get the flag ship product, more than likely you will get a cheap felt from the local builders merchant). Also, the durability rating of rubber roofing falls 10 years behind PVC and again the chance of getting one of the better products will be limited.  With TPO, although the durability is similar to the leading manufacturers of felt and rubber, you can at least have the peace of mind that all TPO installers will have been trained and approved therefore you are unlikely to get an inferior installation. Liquid plastic roofing from all manufacturers we have looked at has a very respectable 25 year durability rating. PVC single-ply membrane has a 30 year plus BBA durability rating. The British board of product approvals seem to think PVC single-ply membrane will easily out last it's rivals.

Finally, Modern Roofing having had experience with most PVC manufacturers, decided to work with SIKA and gain approved contractor status. With SIKA's acquisition of fellow Swiss based membrane manufacturer Sarnafil, we have the two most respected companies in membrane production worldwide under one roof. Modern Roofing have undergone training throughout our company from managers and estimators to tradesman in SIKA's London based specialist training facility, which has resulted in us becoming an approved and licensed contractor.