HOW MUCH DOES A RUBBER FLAT ROOF COST?

A guide to prices. By an expert.

Written by Daniel Woodley. Fact checked by Paul Farley. Published to Prices. Updated: 5th March 2023.

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My name is Daniel, and I have over 18 years of experience in the building trade, including 10 years as a roofer.

If you’re looking for a guide price for a rubber (epdm) flat roof, there’s something you really need to know:

The cost to replace a flat roof on a shed, garage or outbuilding is significantly less than it costs to replace a roof over a heated part of your home, such as a bedroom.

Why?

Because of Part L of the building regulations – this deals with insulation.

In a nutshell, if you replace a flat roof over a heated part of your home, the insulation under the roof must meet the Building Regulations. For many of you, that will mean adding extra insulation and possibly lifting the roof to make space for that insulation, and I know from experience that this isn’t cheap or easy.

Outbuildings, garages and sheds are not covered by Part L.

In this guide, I will do my best to provide you with a realistic price for a new rubber flat roof.

I Also Asked 34 Rubber Roof Installers How Much They Charge

See how much I think a new rubber flat roof should cost

This is a Typical Works Schedule For a Rubber Flat Roof

Below you’ll find a typical schedule for a new rubber roof on a garage, porch or other unheated building:

  • Erect access equipment to the desired work height.
  • Remove the existing flat roof covering.
  • Inspect the existing timber decking boards.
  • If the decking is sound, overlay new OSB decking, so there’s a new, clean surface for the rubber to adhere to.
  • If the decking has sagged, is rotten, wet or in generally poor condition, replace with new OSB decking boards.
  • Install the rubber EPDM membrane to the decking with adhesive.
  • Install black metal edging trims as required.
  • Lower access equipment and remove all waste material.
Rubber roof kit

A typical rubber flat roof kit

Rubber Flat Roof Cost 1: Single Garage

Despite my wealth of knowledge on this subject, I wanted to know how much others are charging for rubber roofs.

I asked 34 roofing firms for a price to replace the covering on a single garage roof with rubber EPDM.

The prices shown below are an average of the figures given to me, and crucially, they include the cost of new 18mm OSB decking.

If the decking on your roof is in good condition, you can lay decking over the top of it, rather than replacing it; this would work out a bit cheaper but not by much.

Location:Price inc VAT:
London and South£1750 - £1950
Midlands and North£1600 - £1800

Rubber Flat Roof Project 2: Double Garage

The prices below are for a double garage, and as with the first price example, they include the cost of replacement 18mm OSB decking.

This is how much I think a project like this will cost, based on an average of the figures given to me:

Location:Price inc VAT:
London and South£3500 - £3750
Midlands and North£3000 - £3250

Project 3: Small Porch

I also sourced prices for a small porch.

Again, the price includes the installation of rubber EPDM and also new decking.

The figures below are an average of the prices given to me.

Location:Price inc VAT:
London and South£800 - £900
Midlands and North£600 - £800

Flat Roof Insulation Cost

The price examples above are for straightforward rubber roof installations where insulation isn’t required.

If your roof needs to meet Part L of the Building Regulations, then the installer may need to raise the roof slightly so insulation boards can be placed under the decking. I would normally install water vapour barrier at this point as well to reduce condensation.

The cost of insulation that meets Part L of the Building Regulations will depend on the specifications of the existing roof and what insulation is currently in place, if any.

Based on my experience and as a general guide, I think you should expect to pay an extra £50-60 per square metre of roof.

Insulated decking

Insulated decking – perfect for roofs above heated parts of the property and meets Building Regulations Part L but costs more.

A good flat roofer, such as one from our recommended partners, should be able to explain what type of decking you’ll need after inspecting the roof but here is a general guide to flat roof decking.

A Note About Decking

The life expectancy of any flat roof covering isn’t just determined by the finishing material or the quality of the workmanship but also by the decking that supports the felt.

I’ve seen countless flat roofs fail early because improper felt or decking was used, so this is an area where I feel expertise is crucial.

OSB decking sheet

OSB Decking is extremely strong, layers of wood are glued together not randomly but to a specific pattern for maximum strength.

Traditional bitumen products can be torched onto old decking boards. However, both rubber and fibreglass should ideally be laid onto new OSB board decking, which obviously adds to the cost of these projects.

The good news is that if the decking boards on your roof are in good condition and aren’t wet, rotten or sagging, they can be left in place and new boards laid over the top of them. This method can reduce the price of the project as removing and disposing of old decking boards is costly.

While some roofers may recommend installing the rubber over old decking boards, I’ve seen this fail many times so I suggest you make sure they are in a good enough condition. Rubber flat roof membranes should never be laid over bitumen or bitumen residue that’s leftover from previous coverings as the contmination may damage the rubber – this is something I’ve seen first-hand.

Additional Costs to Consider

Insulation: As discussed, garages and unheated porches don’t require insulation but a flat roof located above a habitable part of the property will need it. The Building Regulations for roof insulation (Part L) explain in more detail how much insulation is needed but for most flat roofs above heated parts of the property, you’ll have to pay for new insulation. I haven’t included this cost in my guide as the type, quantity and price varies from project to project.

Here’s a quote from SIG Roofing:

Basically, if you’re refurbishing more than 50% of the roof, then Part L comes into effect; the whole of that roof must then be brought up to the thermal efficiency demanded by the regulations.

Access: The prices shown on this page are for porches and garages, which are easy to access. If your roof is located in a difficult-to-access part of the roof, perhaps 3 storeys high or in another area that can’t be reached easily with a ladder then other, more expensive access equipment, such as scaffolding might be needed.

Optional Gravel/Stone Finish: Rubber roofs aren’t the prettiest roofs, and some people dislike the finish – I don’t mind them personally but as an optional extra, gravel or stones can be laid on the roof for aesthetic purposes. This will cost more, and I haven’t considered this in my flat roof price guide.

VAT: The 34 roofing firms that I contacted for prices were an even mixture of larger firms that are VAT registered and smaller businesses and sole traders that are operating below the VAT threshold and don’t need to charge this tax. The prices displayed are an average of the figures and include VAT where charged.

Extras: Most flat roofs will have guttering, roofline fascias and sometimes soffits at the edges. I haven’t included a cost to replace these with Upvc plastic or to paint them. You may want to consider this extra work.

Get Your Custom Rubber Flat Roof Price Online

My rubber flat roof price guide is calculated on figures given to me by firms and sole traders in the UK, but every project is different.

To get a custom price for your replacement roof project, tap the button below and fill in the contact form:

  • Get a rubber flat roof price quickly online.
  • Read vetted ratings and reviews.
  • Compare the prices from three flat roofing firms.

Rubber Flat Roof FAQS

What is The Best Flat Roof Covering Material?

Rubber has become very popular over the last decade or so and is one of the longest-lasting materials. It can be expensive though, especially when new decking is required, and one should be careful not to contaminate it with oils, solvents or residues from old bitumen roofing materials.

Fibreglass is a hard, tough material that lasts for decades but based on my experience, it’s prone to cracking when used on very large roofs where there’s movement of the structure underneath.

Bitumen-based flat roof felts have been around for decades and are one of the oldest and time-tested materials and I’ve installed it onto dozens of roofs. It’s often cheaper than rubber but doesn’t last as long and is more easily damaged by weathering and sunlight. Also, bitumen must be heated with a gas-powered torch which introduces a fire risk.

When Were These Rubber Flat Prices Updated?

I gathered these prices in 2023 and published this rubber roof price guide in January 2023. I don’t expect the prices to change much over the next year or so, except for inflation which is levelling off.

How Long Will a Rubber EPDM Flat Roof Felt Last?

Most manufacturers offer warranties of between 10 and 30 years and rubber roofs installed 20 years ago are still holding up well. In my opinion and based on years of experience, a rubber roof should outlast any other flat roof covering, including fibreglass.

Of course, the life expectancy of the roof will depend on the workmanship and the condition of the timber decking underneath it.

Where Did The Prices Come From?

34 roofing firms and tradespeople from around the UK provided me with prices for rubber flat roofs. I then calculated an average price and published this guide.

Do I Really Need New Decking?

EPDM rubber roofing products should only be laid over sound decking that isn’t contaminated with oils, solvents or residue from bitumen.

If the decking on your roof is sound and clean, you might be able to lay the rubber directly onto it.

The next option is to lay new decking over the top of the old one, this is only possible if the old decking isn’t sagging, wet, rotten or in poor condition. The third option is the most expensive; remove the old decking and fully replace it with new 18mm OSB decking. Each decking sheet covers 2.8 square metres, and each one costs around £45-55 to buy and fit.

My Existing Flat Roof is Pooling Water, Is This a Problem?

Modern flat roof materials are designed to last years, even with water pooling on them.

However, in my opinion, you’ll get more mileage from your roof if most of the rainwater flows off of it rather than pooling on it.

Also, if your roof does spring a leak, it will be far worse if the roof is pooling considerable amounts of water.

If your existing flat roof is holding water in a few areas that have sagged, replacing the decking may solve the issue.

If the roof is designed so water is flowing in the wrong direction, then one end of the roof will need to be raised, so the water flows towards the guttering or outlet. Raising a flat roof at one end isn’t as difficult as it may sound, but new decking and some extra timbers will be required. This will obviously add to the overall cost.

If your existing flat roof is pooling water, contact a roofing specialist, make them aware of the issue and request a flat roof price that includes the cost for new firrings.

How Long Does it Take to Install a Rubber Flat Roof?

Based on my experience, it should take a roofing firm just under a day to replace the decking and felt covering on a single garage. A double garage will take between one day and a day and a half.

Are There Any Associations Where I Can Find Vetted Flat Roofers?

Several roofing associations in the UK hold databases of approved roofers.

The National Federation of Roofing Contractors and the Confederation of Roofing Contractors are good places to start.

You can also use our network of tradespeople, and of course, there’s also Checkatrade, Which?, Trustmark and other general associations.

Why You Can Trust This Guide

I know there’s a lot of nonsense published online, usually by those that have never worked in the industry.

Here’s my experience:

1997-1999: I trained as an installer and fitted fascia and soffit boards and guttering as a roofline installer.

1999-2003: I trained as a flat roofer (built-up systems and fibreglass).

2003-2008: I went self-employed and worked in flat roofing, roofline and general roofing (mostly in domestic settings).

2008-2015: I worked first as a project cost estimator and then as a project manager for a housebuilder and property renovating firm and then for a landscaping company.

2015 onwards: I continued working as a project manager but mostly on larger landscaping projects.

As accuracy is so important, I gathered prices from flat roof installers so I could get a picture of what the going rate is in the UK – I’ve been outy of the roofing industry for a few years and inflation has distorted prices recently.

I also asked Paul Farley to fact-check the important statements I’ve made in this guide.

Author: Daniel Woodley

Daniel has over 18 years of experience in the construction, home improvement, and landscape garden industries, including a spell working as a project manager.

In his spare time, Daniel enjoys gardening, hiking and scrambling. He frequently posts videos to his popular YouTube Channel and is well known in the hiking community.

More About Daniel Woodley.

Daniel Woodley

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