How Much Does A Flat Roof Cost? – The Definitive Guide

New Flat Roof Cost
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Are you are dealing with a leaky flat roof, condensation, or perhaps building a new extension? In which case you’re probably wondering about new flat roof costs. In fact the truth is, exact pricing is complex due to various factors. This guide should help you understand key components impacting flat roof costs and provides ballpark figures for informed decision-making.

Regrettably, there’s no simple answer.

Scouring the internet for a straightforward price might leave you disappointed. Estimates are imprecise, hindering the calculation of flat roof replacement cost.

Why no straight answer?

Flat roof replacements are intricate. Numerous variables affect the price, such as roof size and type, property height, accessibility and location.

At Proactive Flat Roofing, we value transparency. We want you to understand everything necessary for making an informed decision about your new flat roof, including pricing. That’s why we create these articles – to make sure you know how to avoid the cowboys and make the right choice when it comes to replacing or repairing your flat roof.

This article covers flat roof installation costs and factors that impact them, but a site survey is required for an accurate quote.

So How Much Does A New Flat Roof Cost? 

There are many factors that can impact the cost of a new flat roof. The most common considerations when it comes to flat roof cost are: 

  • The size of your flat roof 
  • Access to the roof 
  • Height and safety considerations
  • Whether you’re refurbishing or building a new roof 
  • Your chosen roof type 
  • Waste management 
  • Aesthetic and design choices 
  • Quality of the installer, their processes and their warranties 

So let’s break it down and try to answer the big question “How much does a new flat roof cost?” 

flat roof
Newly insulated Vanguard EcoWarm pvc single ply flat roofing system in Plymouth

The Size Of Your Flat Roof 

Initially, you might have thought calculating flat roof cost was as simple as finding the price per square metre and multiplying it by the roof size. However, as evident from the factors listed earlier, there’s more to consider than just the size.

While the roof’s dimensions matter, other factors also contribute to the final cost. Be cautious if an installer quotes based solely on size, as this could indicate inexperience. Reputable roofers know that other aspects need consideration to provide an accurate quote and ensure a durable flat roof.

I know you’re seeking pricing information, and I won’t disappoint you. I’ll give you a ballpark estimate based on square meterage, but remember, it’s not an accurate guide. Keep reading to understand the factors influencing the cost and gain a better insight into how much a new flat roof truly costs.

Here’s some examples of how much a new flat roof costs based on square meterage alone: 

3m x 5m (15sqm) – £3750 to £4850 

4m x 8m (32sqm) – £8000 to £9750 

5m x 12m (60sqm) – £15,000 to £18,000 

Access To Your Flat Roof 

The accessibility of your roof has an impact on the price. Why? Because not all flat roofs are single-storey extensions with easy access and free parking right outside. 

The cost of accessing a 13-storey roof in the middle of the City of London, where the only access is through an elevator that’s only available for 2 hours a day (yep, that’s a real project we completed!) will be more than the cost for a single-storey home in the suburbs. 

Why? Because the less accessible the roof, the more equipment, manpower and time will be needed to complete the project. 

Less accessible roofs don’t just take more time to install, but they take more planning time too. If you have to go through the house to get equipment, people, materials and rubbish in and out, there needs to be a plan and protection in place for the floors and walls.

This extra time and resource can impact the price of your flat roof installation. 

Height & Safety Considerations

By law, every business has a duty to keep both its workers and customers safe. In order to do this sometimes additional equipment (such as scaffolding) must be hired to keep the project compliant and safe. 

To put it simply, the higher your roof is, the higher the risks – and the higher the cost. 

Scaffolding is a key part of how roofers protect our workers and you on the ground below and the cost can vary greatly depending on your needs. 

Typical scaffolding costs range from £750 for a simple single-storey extension to £1800 to £2250+ as the height/complexity increases.

New flat roof cost
A Vanguard tapered insulation scheme being installed to a new self-build project in Derby.

Refurbishing, Or A New Flat Roof? 

Often in life, refurbishing something is cheaper than buying new. But not when it comes to flat roofing…

Refurbishing a flat roof often costs 10-20% more than installing one on a new property. Why? It’s more complex, time-consuming, involves waste management, and typically requires addressing water damage to the existing roof substrate.

Things that impact the price when you’re refurbishing an existing flat roof include: 

Roof Construction Type 

Flat roof construction and materials used impact the replacement process and, ultimately, the cost.

For example, is your flat roof a typical “cold roof” with a timber structure and insulation between the joists? Or block and beam with screed, woodwool slabs or stramit? The list goes on…

Existing Structural Condition 

Is the underlying structure in good condition with no repair work required, or does it need to be rebuilt or repaired? 

If your roof is of timber construction and has been leaking for some time, you should expect some structural damage and, therefore, repair costs, too.

Prices for these repairs can vary, starting from as low as £150 and going up to £1500+ based on the number of joists requiring repair. Keep in mind that very few jobs require replacing all the joists, so there’s no need for excessive concern. Just stay informed so the cost doesn’t catch you off guard.

The Substrate Type 

The substrate is the structural surface that carries the waterproofing membrane. This can be constructed of various materials – timbers (chipboard, ply, OSB or planks), concrete, stramit (compressed straw) or wood wool slabs (timber shavings sprayed with concrete!) 

Does it need to be repaired or replaced or can it happily take the new roof covering? The condition of your substrate is a key component that will impact your flat roof replacement price. 

To give you an example, replacing and disposing of an existing timber deck that’s 30m2 can cost between £1800 to £2700+ depending on the complexity.   

The Waterproofing Type 

When you’re trying to answer the question “How much does a new flat roof cost?” waterproofing type is definitely something to consider. 

What type of existing waterproofing do you have? Is it a typical mineral felt with reflective chippings that need to all come off and be disposed of? Or does it have a simple mineral felt finish that can take the new insulation and waterproofing layer without the need to remove it? Just these two scenarios can have a significant impact on the cost of your project. 

For example, if you need to remove and dispose of the reflective chippings, then you can expect to add around £17 per square metre to the cost of your flat roof replacement. 

Waste Management Costs 

The cost of removing the waste that’s created by replacing your flat roof is often one thing that’s overlooked when you’re wondering “How much does a new flat roof cost?”

All that old material from your roof will need to go somewhere – and a skip is usually the simplest solution. Typically most refurbishment jobs will require an 8 yd skip, which currently costs between £350 to £425.

Aesthetic, Insulation & Design Choices 

There are many flat roof types on the market today – from the old-school felt or asphalt to GRP (fibreglass), EPDM, Single-Ply… the list goes on. 

Each flat roof type is different – some last longer than others, some are cheaper, some are better at insulating your home and some look better (or worse!) You can learn more about the specific flat roof types, as well as their benefits, downsides and prices on our blog here. 

But to give you an indication of how the flat roof type can indicate the cost of your flat roof replacement, here’s a rough guide for a 30m2 flat roof: 

  • Mineral felt (average lifespan 1-8 years) – £4500 to £7500 
  • Fibreglass (GRP glass reinforced plastic) (average lifespan 1-15 years) – £6000 to £8000 
  • EPDM (Ethylene Propylene Diene Monomer, Synthetic Rubber) (average lifespan 5-15 years) – £5500 to £8000
  • PVC Single Ply (average lifespan 20+ years) – £7500 to £9000

So as you can see, it’s not all about how much the flat roof costs initially, but how much it will cost you over the next 10, 15 or 25 years. To learn more about how long each flat roof type lasts, read this article here.

New flat roof cost
Vanguard EcoWarm roof system being fixed to an existing bungalow in Bristol.

Credibility, Quality & Guarantees  

Another major consideration that will impact the cost of your flat roof replacement is the standard of installer you choose to work with. 

The flat roofing industry has many unscrupulous individuals who take your money and provide a low-quality, temporary solution – or, in the worst-case scenario, a botched job that requires immediate replacement.

To make sure you entrust your property and project to a reputable flat roofing company, opt for one with accreditation, experience, and with a proper back office infrastructure to manage and support more than one job at a time, oh and a lengthy insurance-backed guarantee.

Nevertheless, choosing a reputable flat roof installer will be more costly than a cheap “one man band” installer – but in the long run, it can save you thousands of pounds in repair costs, replacements or even structural damage that can occur from a poorly installed roof. 

To learn more about what to look for in a reputable flat roofing company check out our blog post here

Newly completed self build project with insulation and Vanguard pvc single ply waterproofing system.

So How Much Does A New Flat Roof Cost? 

As we’ve explained above, determining flat roof costs is challenging due to various factors. For an average-sized roof (20sqm), expect to pay £3,000-£7,000 for a simple, single-story installation. Costs may rise with access or construction issues.

Commercial properties and large projects have unpredictable pricing, ranging from £5,000 to over £500,000. Obtain a flat roof survey for an accurate quote.

Your Next Three Options To Discovering What Your New Flat Roof Could Be

  1. Claim your free guide to Flat Roofing here then…..
  2. Book your free flat roof survey or email us your plan [email protected]
  3. Online Quote Generator

After your survey, you’ll receive a free 23-point roof Condition Report, Action Plan, and comprehensive itemised Quote worth £295+vat.

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