Flat roof replacement

Flat roof replacement may be necessary if a flat roof is damaged beyond repair or at the end of its lifespan.

There are many things to consider when carrying out a flat roof replacement, such as the advantages and disadvantages of GRP roofing and other materials. Many experts consider EPDM roofing to be the best material to use for a flat roof replacement due to its cost and durability.

Below we discuss your options.

What is a flat roof?

A flat roof looks perfectly horizontal to the eye but actually has a slight slope. Most flat roofs will be pitched up to as much as a 10-degree angle which helps water drain away from the roof’s surface. The slope helps to prevent potential issues such as water ingress and blistering occurring.

Flat roofs are common on extensions, garages, conservatories and outhouses. There are many benefits that flat roofs offer compared to the alternative roofing options, such as lower construction costs. This is due to flat roofs taking less material and time to construct than pitched roofs.

Flat roofs can also have a dual purpose, with many homeowners opting to use the top of the roof as a balcony or terrace. Although this is usually subject to planning permission.

Flat roofs can be made from several different types of materials, from EPDM roofing to felt roofing. Each type of material has its own set of advantages and disadvantages which can determine the cost, longevity, and reliability of the flat roof.

If a flat roof falls into disrepair, it may be time to carry out a flat roof replacement – although it’s always best to consult with a professional roofer before taking any drastic action.

Most flat roofs will need to be replaced every 20 years or so depending on the material it’s made from. A flat roof replacement will typically be needed if there are signs of damage to the roof’s surface, large-scale pooling, or issues with the seams.

Should I repair or replace my flat roof?

Whether you should repair or replace your flat roof will depend on several factors, such as the extent of the damage to your roof.

My Local Toolbox always advises consulting with a professional roofer when deciding between a flat roof repair or replacement. They will be able to tell you the pros and cons of each option and work out which will be the most cost-effective and beneficial to you in the long term.

Here are five key factors that may determine if you need a flat roof repair or replacement:

1) Water leakage: A sign of fundamental problems with your flat roof which can cause major structural issues if left untreated.

2) Bubbling & blistering: Evidence of water getting under the surface of the roof, potentially leading to a build-up of mould and other algae in the future.

3) Flashing damage: Generally caused by harsh weather conditions, a damaged flashing means there’s less protection to the most vulnerable parts of the roof.

4) Damaged roof surface: The quality of the roof’s surface will determine the level of protection provided to the underlay and interior walls. If the surface is in a worn condition, it could lead to other issues arising as a result.

5) Age of flat roof: Simply, you may have to carry out a flat roof replacement due to the age of your roof. As time goes on, your roof will pick up wear and tear issues that can’t be repaired.

Lastly, another factor to consider when deciding between a flat roof repair or replacement is if there’s evidence of asbestos.

If there is, an asbestos removal specialist will be able to take care of the issue before a roofer begins your roof repair or replacement.

What’s involved in replacing a flat roof?

A flat roof replacement will normally take between two and three days, depending on the size of the roof, its current condition and the materials used in its construction.

However, before you begin a felt roof replacement or a firestone rubber roof replacement, for example, you’ll need to remove your existing roof. You may find a skip stationed outside your home to store and transport excess materials from the demolition.

Felt flat roof replacement

To protect your home during this process, your roofer will most likely use additional waterproof measures until the flat roof replacement is complete.

The next step is to begin the construction of your new flat roof. No matter which roofing material is being used, it’s always a good idea to clean the surface on which the roof is to be laid.

This will ensure it will fit squarely onto the underlay. Your EPDM roofing, GRP roofing or asphalt roofing will then be installed onto the roof’s frame, providing an outer layer of protection.

Lastly, gutters will be installed, and the outer layer of the roof will be sealed to avoid water leakage.

The other important part of the flat roof replacement process is insulation, whether you’re using felt, fibreglass or EPDM rubber to construct your flat roof.

The first thing to think about is the pros and cons of a warm roof vs cold roof: what’s the difference?

Warm roof insulation is installed above the substrate layer with only the waterproof layer above, helping to protect it.

On the other hand, cold flat roof insulation is situated between the internal finish and substrate board.

Of course, there are also insulation regulations to consider. Cold flat roof insulation regulations stipulate that the thickness of the insulation depends on the material you use to construct your roof, so it’s always best to seek the advice of a professional roofer. It’s the same story when it comes to flat roof insulation thickness building regulations.

What to consider when replacing a flat roof?

Without a doubt, the main thing to consider when planning a flat roof replacement is the type of material to use, as it will dictate a large proportion of the cost.

There are several different types of roofing, each with different advantages and disadvantages to think about. Some of the most common are:

  • EPDM rubber roofing
  • GRP fibreglass roofing
  • Asphalt roofing
  • Felt roofing

EPDM roofing

EPDM roofing is one of the best materials to use if your primary goal is to ensure your roof replacement lasts the test of time. A rubber flat roof has a life expectancy of around 50 years and is extremely durable.

A Firestone rubber roof in particular is extremely hard-wearing and offers watertight protection to your home all year round.

There are some disadvantages of EPDM roofing, such as they’ve been known to pick up damage easily and be liable to shrink in exceptional circumstances.

GRP fibreglass roofing

GRP roofing on the other hand is extremely hard to damage due to its durability and strong outer surface. If your roof replacement is a fibreglass flat roof, the risk of falling victim to water leakages will be reduced. This is because GRP fibreglass roofing can be moulded to the shape of the roof, creating one seamless material rather than a series of materials stuck together.

Disadvantages of fibreglass roofing include a relatively high cost and a low lifespan of around 30 years.

GRP fibreglass flat roof replacement


An asphalt flat roof is another roofing material to consider, with its main benefit being that it’s extremely easy to repair. This is perhaps just as well, as they only tend to last around 15 years due to the thickness and composition of the material before needing a roof replacement.

If you’re currently thinking “should I get a felt or fibreglass roof?”, the best thing to do is to contact a roofing professional using My Local Toolbox. They’ll be able to give you advice on what option is best for you.

Other factors to consider before work on your flat roof replacement begins includes the time it will take to complete.

Luckily, due to the nature of flat roofs, it’s unlikely that this will be much of a hindrance, with most completed within three days.

However, it’s always a good idea to ensure that you have the days that the tradesperson needs access to your property free to give them entry etc. It’s also wise to think about if you would like to use the surface of the flat roof as a balcony or terrace, adding more living space to your home.

Flat roof replacement FAQ

What is the best material for a flat roof?

Most experts believe the best material for a flat roof replacement is EPDM rubber roofing due to its many benefits.

EPDM roofing is more affordable than most other types of roofing materials such as fibreglass while also being one of the most long-lasting and flexible to use.

Due to the durability of EPDM rubber roofing, it requires relatively low maintenance which can often be carried out by simply sweeping the surface and using a bucket of water to get rid of any marks left behind.

However, despite the many benefits, there are still some disadvantages of EPDM roofing that you should consider when considering it for a flat roof replacement.

Firstly, the appearance of a rubber flat roof can be rather unappealing, although this can normally be overcome with acrylic paint.

The surface of rubber roofing can be rather delicate, so it can be at risk of being punctured by falling branches, twigs, or other debris.

Is there any maintenance required with rubber roofing?

Yes, it’s recommended that you carry out regular maintenance on an EPDM rubber flat roof twice per year. Luckily, EPDM roofing is one of the easiest to carry out compared to other roofing types due to the smooth surface of the rubber flat roof and its ability to withstand harsh weather conditions. Here’s the best way to maintain rubber roofing:

  • Sweep all debris from the rubber roofing, including any that has fallen into the guttering.
  • Check the EPDM roof for damage to flashings or sealant. If any are damaged, it’s important that you quickly replace them to avoid further issues.
  • Clean the rubber roofing using dish-washing detergent and a garden hose or buckets of water, making sure to remove any build-up of mould or algae.

If rubber flat roof maintenance isn’t carried out on a regular basis, there’s a possibility that you’ll have to carry out a flat roof replacement before it’s at the end of its natural lifespan.

Also, there are some disadvantages of EPDM roofing that you should be aware of when conducting regular maintenance. Firstly, although the material is extremely durable, it’s still culpable of being damaged in inhospitable weather conditions.

If you’re still not sure whether to opt for a flat roof replacement or a pitched roof, head over to our roofing page.

However, if you want to know how to plan for the costs involved in a flat roof replacement, our flat roof replacement cost guide has you covered.

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