Roof Types Explained

A Guide To Understanding Your Roof



Knowing what type of roof you have and what is causing the leaks can be a daunting prospect.

Below you will find some helpful information explaining the different substrates and what can be the most common types of problems with them.

Corrugated fibre cement sheets are a common roof covering in  commercial and industrial buildings with many containing Asbestos Fibres.

Not all fibre cement sheet roofs contain Asbestos, but we like to presume they do until a test proves otherwise. However, if installed prior to 1999 there is a good chance your roof contains some ACM (Asbestos Containing Materials). There is a relatively inexpensive test that we can carry out to determine this.


As it ages Asbestos sheets become quite absorbent and retain water, also live growth and moss deposits can act like a sponge exacerbating the problem. Cracked and broken sheets are also an obvious sign of leaks.

When initially installed, corrugated roof sheets have holes drilled at regular distances to enable a bolt (commonly a J bolt) to go through the sheet and hook on to the purlin below. Then, the installer would use rubber grommets (washers) to seal the hole. But over time these rubber grommets become perished due to UV rays, age, and general weathering and they break away. There are often hundreds or thousands of these on any one roof. Once they break away you have an uncovered hole and most likely some water ingress at seemingly random points across the roof.

Other areas

that can cause problems are roof-lights. Sometimes there are cracks in or around the roof light due to age and environmental damage. Gaps can appear between the sheets or the roof-light and the sheet adjoining it. Loose flashing and poor joints along neighbouring buildings can also be a cause of leaks.

If you have vents, chimneys, plant, ducting or any other protrusion coming through the roof from the inside to the outside these can cause water to come in to the building if improperly sealed.

Lastly it is not always your corrugated sheets that will cause problems inside your building. Gutters are a much-forgotten element in rainwater movement. Blocked or cracked gutters or gutters with an insufficient fall can cause problems inside the building.


We successfully remedy all these issues on corrugated fibre cement roofs with a very cost effective zero disturbance method involving state of the art liquid waterproofing technology.

Asbestos Waterproofing has been our speciality for over 10 years.

Metal roof sheets are a good option for covering a building. They are strong and solid and come with long guarantees. However, they can also be prone to leaks and deterioration without the proper maintenance.


Metal roofs can fail due to cut edge corrosion. During Manufacturing, the cut ends of the metal sheets remain untreated. This leads to the exposed cut edge of the sheet corroding and the Plastisol coating begins to peel and flake.  These loose flakes, in severe cases, begin to fill the gutters and block outlets.

Once Cut edge corrosion has begun it needs treating to stop leaks already occurring and prevent further corrosion.

You will find cut edge corrosion at the open edge of a sheet and around roof-lights. If you have rust coloured streaks on the outside or inside of your metal roof there is a good chance you have some cut edge corrosion.

In some cases

it is the bolt heads that corrode leading to potential leaks and further decay. Other areas that can cause problems on metal roofs are seals around roof-lights. Protrusions through the roof such as chimneys and ducting. Any plant that has been retro fitted to a metal roof has the potential to leak if the fixings  have perished over time. Loose flashing or poor joints against neighbouring buildings can also be a place for leaks to occur.

Problems can also arise in metal gutters due to standing water, corroding surfaces, blocked outlets or insufficient falls.

Condensation is frequently mistaken for leaks. A combination of cold temperatures outside and warm temperatures inside can often cause condensation on metal roofs that Poorly insulated.


We have successfully treated all the above issues using state of the art liquid coatings. These specialist coatings come with 10-25-year manufacturers guarantee allowing you to focus on maintaining your asset and growing your business.

Traditionally flat roofs have been covered with a layered felt, asphalt or more recently single ply and EPDM membranes. On a flat roof, damage often goes unnoticed for considerable time as water penetrates and soaks the decking and any insulation and/or structure beneath. This can lead to expensive damage from the rot which often develops and if left can weaken the roof structure.

Flat roofs

are relatively easy to maintain, as long as there is sufficient fall to the outlets and gutters. in some cases buildings and roofs can settle over time and the original fall becomes insufficient to carry the water away to the outlets, resulting in ponding or standing water. This can damage and deteriorate the roof covering over time. Problems can also arise from loose flashing and insufficient joins to Neighbouring buildings or structures.


Historically torch on felt systems were used to provide the waterproofing. Felt itself is a good product but the application of it involves hot works which many people now refuse to accept onsite.


ages through photo-oxidation accelerated by heat. As it ages, the asphalts melt point rises and there is a loss of plasticizers. As mass is lost, the asphalt shrinks and forms a surface similar to alligator skin. Asphalt breaks down slowly in water, and the more exposure the more rapid the degradation.

TPO (Single Ply)

This roofing material can be fully adhered, mechanically fastened, or ballasted. TPO seam strengths are reported to be three to four times higher than EPDM roofing systems. This is a popular choice for “Green” buildings. It is available in white, grey, and black. Single ply membranes are are starting to be replaced in favour of Liquid systems due to liquids seamless versatility and application speed.

GRP- Fibre Glass

is is a single-ply GRP laminate applied in situ over a good quality conditioned plywood or OSB deck. Unlike other roofing materials, GRP is not really a roofing material and has properties that render it better suited to small craft construction. It is often used on small domestic installations, but usually fails prematurely when used on larger scale projects.


is a synthetic rubber most commonly used in single-ply roofing because it is readily available and simple to apply. When properly applied in appropriate places, its warranted life-span has reached 30 years and its expected lifespan has reached 50 years

Visit our Projects Page for Examples of Flat Roofs We Have Completed

Why Liquid Coatings ?

With all the options available it can be a mine field trying to make sense of all the information about roofing.

Liquid applied waterproofing membranes are undoubtedly the future of roofing technology.

With the ability to refurbish existing buildings at a fraction of the cost of traditional systems and with lengthy manufacturers guarantees it is becoming the choice of specifiers on all types of buildings. Allowing for much more freedom in architectural design.

Liquid applied waterproofing membranes have been used in the US market for 20 years with great success.


The process of liquid roofing provides a cost-effective method of making a new or existing roof waterproof.

Liquid waterproofing systems can deliver up to 25 years performance depending on the coating system employed. Estimates show that it is up to 70% less expensive than overall replacement.

There is a significant reduction in labour and access costs due to speed of application.  Achieving, in some cases, up to 1000 m2 per day on flat roofs.


In the United Kingdom, the leading testing and approvals house the British Board of Agrément (BBA) has been issuing approvals for liquid roofing systems since 1975.

When quality products, applied by experienced applicators, from a reputable company are employed, you can have peace of mind that your asset will remain protected.


Unlike the installation processes of traditional felt, asphalt and bitumen membranes, liquid waterproofing does not involve hot works. Hot work on roofs is an extremely high-risk process. It poses a significant fire risk to contractors as well as the building and its occupants and many institutions no longer allow hot works on their premises.

The coating material used in the liquid roofing process is cold applied, thus negating any fire risk.

Many of the liquid systems we use are VOC free and solvent free.


When applied, liquid waterproofing systems envelop the surface, preserving whatever is underneath and protecting it from weathering.

This is especially desirable when dealing with Asbestos roofs, as attempted removal of asbestos roofing can damage it, releasing material that can cause Asbestosis.

Using a liquid coating system instead seals the asbestos, therefore making disturbance of the material more difficult.


Using a liquid waterproofing system is beneficial on all substrates due to its fluid nature. The buildings angles and shapes are effectively coated creating a seamless waterproofing seal

Traditional waterproofing sheet membranes are difficult to fit in and around corners and angles. Therefore, any cut in the sheet is a potential leak. The specialist liquid systems we use completely alleviate these problems.

With lengthy manufacturers guarantees and our expert manufacturer approved application methods we are at the forefront of liquid waterproofing.

Our expert team will work with you to repair and refurbish your roofs, ensuring as little disruption as possible to your business, as well as providing a cost effective and long term solution. It pays to get a quote from Elite Waterproofing.