How Much Does It Cost To Replace A Flat Roof

Our aim in this article is to help you understand the question “how much does it cost to replace a flat roof” whilst breaking down the exact costs involved with repairing or replacing a flat roof.

There are lots of different factors that go into figuring out a flat roof cost estimate but we’ll try and simplify the entire process.

From cost examples to the best types of flat roofing systems, we’ll dive deep into making sure you have everything you need to make the best decision possible for your individual property.

The image below shows a flat roofing project that our team at SPS Roofing Ltd completed near Exeter in Devon. The reason for displaying this image is to show we deal with flat roofs on a daily basis and get asked a series of common questions from our customers, and hope to pass our real-life experiences to you.

Flat roof replacement costs
Flat roof replacement costs

How much does it cost to replace a flat roof?

In this article our aim is to help you understand:

  • What Is A Flat Roof?
  • What Are The Benefits Of A Flat Roof?
  • When Does A Flat Roof Need To Be Replaced?
  • Repair vs Replacement – Which Is Best?
  • Flat Roof Replacement Cost Guide
  • Flat Roof Repair Cost Guide
  • Other Costs To Consider
  • Best Types Of Flat Roof Systems
  • How To Choose A Flat Roofer

What Is A Flat Roof?

Many homes and commercial buildings across the United Kingdom have a common feature – a flat roof.

People often think of flat roofs as being completely flat, however they do have a very slight pitch to enable rainwater to drain away efficiently. The last thing anyone wants are water pools on the flat roof surface leading to the steady breakdown and decay of the material itself.

Flat roofs are typically found on extensions, garages, dormers, balconies, carports and outbuildings. They can be very cost effective and slightly more flexible than a traditional pitched roofing system.

Many of our customers are led to believe that flat roofs are not as durable as slate and tiles but we feel differently.

If the correct material, system and roofing contractor is chosen, with the appropriate approvals such as Bauder, then a flat roof can last in excess of 25 years.

Combining this lifetime vs the cost and you can see a flat roofing system will often be a great choice for certain types of building and use cases. If you are unsure as to whether or not you should choose a flat roof or pitched roof, then please feel welcome to contact SPS Roofing Ltd for advice and flat roof estimates.

So now we’ve covered exactly what a flat roof is and where they are typically found, let’s explore the benefits…

Benefits Of A Flat Roof

There are many benefits for installing a new or replacing an old flat roof. There are good reasons for why they are one of the most popular systems in the UK.

  • Cost Effectiveness – typically a flat roof takes less time to install and require less materials than a pitched roof. As a result this will mean it costs less to install or replace. Of course this depends entirely on the area size, materials uses, application techniques, commercial vs domestic, and various other factors.
  • Flexibility – easy to install on most roof types and sizes helping to cope with the natural contraction and expansion of building movements.
  • Durability – with the right material / system chosen you can expect to find a flat roof to be very durable, long lasting and offer protection against harmful UV rays.
  • Little Maintenance – similarly to the above point, depending on the system, you can expect hardly any maintenance once post flat roof installation. Please note that this depends on the quality of whoever installed the flat roof. Later in this article we’ll show you how to choose a reputable flat roofer to avoid the potential cost associated risk of losing money hiring a poor contractor to construct your flat roof.
  • Additional Living Space – you can even use a flat roof to add an additional space to your home or commercial building (depending on the system). For example, eco friendly green roofs give ultimate versatility by allowing the owner to have a rooftop patio, garden and pathways with real-life vegetation.

Some of our customers often ask if there are “any significant disadvantages” to choosing a flat roof? We want to be perfectly honest with you by breaking this down. If you have chosen a reputable roofing company with the appropriate accreditations, ratings and approvals then you should be good to go.

For example, here at SPS Roofing Ltd our roofers in Exeter hold certification/approvals with Bauder, Constructionline, CSCS, NFRC, CITB, SMAS Worksafe Contractor and City & Guilds.

However, we have seen numerous cases where a customer had initially opted for the “cheaper alternative” to later find multiple problems (e.g. roof leaks, cracks, water pools, etc). 9 times out of 10 most people will say something bad about flat roofs based on their own negative past experiences. We understand it is extremely frustrating when you have trusted someone to do a job correctly, and later find out they performed poorly.

If you have had to find out the hard way and are reading this article because of a ‘rogue roofer’ then feel free to give us a call for advice. There may be options available where you don’t need to fork out another £2000 or more to replace it.

Flat Roof Replacement Cost By SPS Roofing Ltd (Exeter, Devon)
Flat Roof Replacement Case Study

How Do You Know When Your Flat Roof Needs Replacing?

Most of the factors to decide whether or not you should replace a flat roof may seem obvious, and in truth they are. Either way we want to ensure that you understand if you need to find an estimated flat roof repair cost or flat roof replacement cost.

Before we dive into it, these points have been created from our own flat roofers experiences over the last 25 years.

Some of our previous customers had left their roof alone even though they knew about a small leak or damages. Please do not do this. Through leaving your flat roof leaking for a prolonged period of time not only weakens the wooden timbers through rot, but can lead to a much higher replacement cost in the future.

1) Flat Roof Leaking

Common Verdict = flat roof replacement

I know that might not be what you want to hear but most of the time we have tended to a job with a significant flat roof leaking problem we have had to replace it. Typically we would have to remove the material (e.g. felt) from the surface to inspect the roof timbers and for other internal water damage.

We strongly recommend getting a qualified roofer to inspect the structure of the building to ensure it’s sound enough to install the replacement. For example, check if the roof timbers are not rotting away or significant damp/mould.

2) Water Pools & Flooding

Common Verdict = flat roof repair / replacement

This can be a reasonably low cost job. This problem occurs when you see your flat roof gathers water pools instead of draining off into the gutters. It is absolutely vital that you have your pitch altered slightly to ensure the water drains off the surface.

However, in addition to our common verdict, we want to say that this does depend on how long the water pools and flooding have been occurring. If water is left too long, and consistently, we have found that leaks and rotting can take place. If this has happened you may need to invest in a new flat roof.


3) Unwanted Vegetation Growth

Common Verdict = flat roof repair

If you start seeing growth of moss, algae, lichen, fungus, mould or other weeds, it might be time you get your flat roof replaced. This problem normally occurs due to a build up of water where this type of vegetation thrives. Sometimes it can be so deep routed you need to replace the whole roof to avoid the unwanted vegetation returning in a few months.

4) Cracking, Stretching & Blistering

Common Verdict = flat roof replacement

This is the last thing anyone wants to see on their roof and it’s a very obvious sign your flat roof is in a serious need for an upgrade. Over time the materials are exposed to harsh weather and UV rays which causes the waterproof layers to crack and tear away. We have seen this quite often on rubber flat roofs such as EPDM.

This also applies to any building movement. If you have noticed, especially with an older property, that the structure itself has moved it often leads to tearing and cracking the flat roof material.


5) Outdated Flat Roofing System

Common Verdict = flat roof replacement

Compared to even 10 years ago, there have been so many technology advancements when it comes to flat roofing systems. Nowadays there are so many options available for people to choose between it can often be tricky to pin down the best materials for your use case.

When a flat roof becomes old it will show signs of wear and tear, as we discussed above. With a qualified roofer you should be able to upgrade your flat roof at a reasonable cost.

Here at SPS Roofing Ltd, we normally recommend 3 flat roofing systems: Single Ply, High Performance Felt & Liquid

We will explain the advantages and disadvantages to these systems below and how much does it cost to replace a flat roof with them below.

Flat Roof Replacement Cost

There are many factors to consider when trying to price an estimate for the cost of flat roof coverings and replacement.

  • What flat roofing system and materials you choose
  • How easy is the roof to reach
  • The area size of the flat roof in M2
  • The location of your project (South East is more expensive than North East for example)
  • Roofing companies vary in costs
  • Old flat roof removal costs
  • Other waste removal costs (usually handled by contractor)

Single Ply Flat Roof Replacement Cost

Single ply has been our go to choice for replacing flat roofs. So how much do single ply flat roofs cost?

The answer is… it depends!

First of all we’ll explain a little about what Single Ply Flat Roofs are and why they are our top choice of material.

The single ply system work great for almost any type of application including new builds, extension flat roofs, garage flat roofs, etc. Contact us to get a better idea of how does it cost to replace a flat roof with single ply.

It’s extremely strong, durable and the flexible PVC sheets are manufactured of mainly synthetic polymer welded so it’s completely seamless, and hence waterproof. Furthermore the benefits received such as insulation make this a top choice for replacing your flat roof.

Single Ply Flat Roof Replacement Costs:

There are 2 methods of application, and the cost varies depending on the application method.

Warm Applied Price = £80 per m2 – £120 per m2

Cold Applied Price = £60 per m2 – £80 per m2

Click here for a free flat roof replacement quote.

Single Ply Flat Roof Example

Felt Flat Roof Replacement Cost

How much does a felt flat roof replacement cost? Again, depends on the size of roof.

In some cases we would recommend against the use of felt for larger roof area sizes (m2) and switch to a single ply system. We have seen people charge £1,200+VAT right the way to £12,000+VAT. Be careful by making sure you get a few quotes first to price compare.


Felt Flat Roof Replacement Costs:

There are 2 methods of application, and the cost varies depending on the application method.

Warm Applied Price = £120 per m2 – £160 per m2

Cold Applied Price = £80 per m2 – £100 per m2

Click here for a free felt flat roof quote today.

Liquid Flat Roof Replacement Cost

Our liquid systems are typical cold applied, highly waterproofed with seamless fitting, versatile and great for multiple use cases including balconies, walkways, high traffic areas, roof terraces, new extension roofs, etc.

How much does a liquid flat roof replacement cost?

Hot Melt System Price = £90 per m2 – £100 per m2

Liquid System Price = £130 per m2 – £150 per m2

Click here for a free liquid flat roof quote today.

Flat Roofing Replacement Cost
Flat Roofing Replacement Cost

Green Roof Replacement Cost

A green flat roof is a real life, living eco friendly system that encourages nature, blends in with natural surroundings, improves the aesthetics of a property and improves a building thermal and acoustic performance. There are many benefits of a green roof and we can design it for you based on your requirement.

Due to there being so many green roofing options it’s very hard to pin point an exact price but we have seen it range from £80 per m2 to £140 per m2. Again, just to reiterate, this depends on the size of roof, the specifications and the amount of vegetation (plus use case) requested.

Green Flat Roof Replacement Costs:

Green Flat Roof Sedum Blanket Price = £55 per m2 – £70 per m2

Substrate Green Flat Roof Price = £70 per m2 – £100 per m2

Click here for a free green flat roof quote today.

Green Roofs Exeter and Devon - SPS Roofing Ltd
Green Roofs Exeter and Devon – SPS Roofing Ltd

Flat Roof Repair Cost

Rather than give you an arbitrary figure for an average flat roof repair cost (which is nearly impossible without looking), we feel it would be better to give you a checklist you can follow to prepare yourself for contacting a roofing company.

A flat roof will need to be repaired if you experience water leaks, internal damage, wooden timbers rotting, water pools, etc.

In general, if a flat roof is left too long with one of the above problems it will lead to the repair cost being substantially higher. For example, if you left a flat roof water leak for 1 year it can impact the structural soundness of a building due to water rotting the wooden timbers beneath.

Here’s a DIY flat roof inspection checklist for you to follow to determine whether you need flat roof repair or replacement:

  1. Signs of punctures – a rusty nail for example.
  2. Rips, tears and cracks – usually due to harsh weather, UV rays and building movements over time.
  3. Damaged or missing flashing
  4. Visible sagging – normally in the middle of the roof.
  5. Water pools and leaks
  6. Faulty gutters and downpipes
  7. No sealing or gaps between layers
  8. Length of time problem has occurred – or since last upgrade

If you can see you have any of these problems then it might be time to call a qualified flat roofer to inspect further. Depending on the scale of the problem the flat roof repair cost can range from £150 all the way up to several £1000.

Beware of Rouge Flat Roofer Contractors

We see some of our customers had made the unfortunate error of going with a local contractor, who appeared to know exactly what they were doing.

When asking how much does it cost to replace a flat roof you should not only consider the points we discussed earlier in this article, but how capable and qualified is the contractor.

To help potentially limit the risk to you falling for this ‘trap’ these so-called rogue tradesmen use we have complied a list of question you should ask.

  • How long have you been replacing flat roofs?
  • What’s the average cost of replacing a flat roof?
  • What qualifications do you have? (ask for proof)
  • What accreditations and approvals do you have? (these are different from qualifications and often harder to get, so will divide the poor tradesmen to the great).
  • Ask for previous customer reviews and if possible numbers to either text or call to confirm the legitimacy.
  • Ask for pictures or videos of previous flat roofing jobs they have worked on.
  • Request a full quote breakdown with the exact materials to be used and labour costs.
  • Will the old flat roof material (e.g. felt) be removed before the new layer.
  • Are there any other associated costs not included in the quote?

If any of these important questions are answered vaguely or without the appropriate proof, then you can move onto the next roofing company to save yourself the potential cost of having to rectify mistakes made due to a poorly skilled tradesman.

Conclusion – Replace A Flat Roof Cost?

To conclude how much does it cost to replace a flat roof we have explored what exactly a flat roof is, the benefits of flat roofs, how to know if a flat roof needs replacing, flat roof replacement average costs and flat roof repair average costs.

We understand that you may have several other questions for us such as how long does a flat roof last? Do flat roofs leak more? How often does a flat roof need to be replaced? Are flat roofs expensive? Are flat roofs fire proof? Are flat roofs covered by insurance? How often should you seal a flat roof? What’s the best flat roofing material?

If are still asking yourself these questions or would like to confirm anything with us, then please feel more than welcome to contact our Exeter roofers in Devon today.

WE ARE NOT LIMITED TO LOCATION and will be happy to assist with any projects across the United Kingdom.

Looking For A Qualified Roofing Company?

SPS Roofing Ltd is a highly rated roofing company based in Exeter operating across Devon and South West England including Somerset, Cornwall, Wiltshire, Gloucestershire and Dorset.