Garages are useful places to store many things, including kids’ bikes or your vehicle. You can even use it as a hobby room. Usually, they’re sturdily built, but they aren’t habitable. So, many builders use flat roofs that only last 10 or 15 years and cost far less than a pitched roof with tile or slate, that might last 50 years. But, of course, sometimes a cheap roof is all we can afford. A bitumen felt garage roof costs about £450 for materials and £350 for labour. Therefore, the total cost of a new garage roof in the UK is about £900 to £1000. Surprisingly, you won’t find the job takes very long. A straight felt replacement takes about 1 day for two men, give or take a few hours.
It’s also easier to build a flat garage roof. It’s cheaper, lightweight and a flat roof needs shallower foundations than pitch roofs because they’re supporting less weight. And, balancing the cost of replacing the felt every 15 years or so against building stronger foundations, thicker external walls and a proper tiled roof is a complete no-brainer. A flat roof replacement will win out every time.
Flat garage roofing isn’t really flat. It has a slight slope to allow rainwater runoff. However, even with runoff, the bitumen felt degrades under the influence of water, and sunlight. This causes the felt to become brittle and crack, thus allowing water leaks to the timber beneath.
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Usually, there’s no way for the owner to know if the timber roof structure is rotten, without removing the felt. Therefore, the best way to keep maintenance up to date is to keep an eye on the state of the felt. When it turns brittle, it’s time to replace the roof.
Main Topics
How Much Does a Garage Roof Replacement Cost?
It’s important when removing and replacing the roof covering to check that all timber is sound. If not, replace the wood before refelting the roof. If you need to replace any garage roof sheets then add on an extra £40 per 2.4m x 1.2m plywood board.
So far we’ve just talked about standard cheap bitumen felt. And, this, together with asphalt are how all flat roofs used to be made. However, in recent years more and more flat-roofed garages now use EPDM (a rubberised membrane) and GRP Fibreglass. Before we move on, you should know that felt and asphalt roofs have both improved with advances in technology, and are no longer the problem materials we used to have.
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New Garage Roof Costs
The following table shows typical costs for single and double garages using different roof coverings. Don’t worry if your garage is a different size to these, as you can calculate cost estimates for your replacement garage roof. Do this, by multiplying the cost per square metre by the area of your garage roof.
| Type of Garage | Task | Cost/m2 | Total Estimated Cost |
|---|---|---|---|
| Medium single garage 2.7m x 5.5m | Fibreglass roof | £100 | £1,485 |
| EPDM Rubber roof | £90 | £1,336 | |
| Felt roof | £50 | £742 | |
| Standard Double garage 6m x 6m | Fibreglass roof | £100 | £3,600 |
| EPDM Rubber roof | £90 | £3,240 | |
| Felt roof | £50 | £1,800 |
Garage Roofing Materials – Options & Considerations
According to the experts, there isn’t a ‘best’ flat roofing covering. But, there is a type of flat roof covering that suits your particular garage. This means, the unique size, shape, detail level, and of course your budget.
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So, let’s look at the most common roof coverings.
Felt
This is a low–cost roof covering with proven results. It’s cheaper than the others and will suit just about any roof size.
However, it needs heat for application. Also, it’s not suitable for a DIY roof, and not strong enough for regular footfall. Finally, modern felt roofs suffer from the poor reputation of older systems.
EPDM rubber
This roof covering is very lightweight, flexible and hard-wearing. Furthermore, you don’t need heat during the application, and it’ll last a long time.
However, it’s not a pretty material to use and neighbours might complain if they overlook it. It might shrink with age and doesn’t complement complex detailing. Because you don’t need special equipment, it sometimes attracts cowboy installers.
GRP fibreglass
This is a lightweight, and hardwearing covering. You don’t need heat to install it and it has no joints. Furthermore, it is very vandal-proof, looks good, and has a long lifespan. If you have DIY skills, this roof shouldn’t be difficult to install.
However, the covering isn’t flexible and doesn’t work well with large areas. Also, can be slippery when it’s initially installed.
As you can see, they each have their attractions depending on how you want the finished job to turn out. If your main consideration in the short term is the price, then go for a felt roof. But, if you want a hardwearing roof then GRP fibreglass or EPDM is probably the best. It’s up to you.
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Types of Garage Roofs
Let’s have a look at some of the different roof types before we go any further. We’ll start with a flat roof.
You can make a flat roof support structure from different materials before it’s covered with the chosen roof covering. The most common structure uses 150mm x 75mm joists set 450mm apart.
The slope of a flat garage roof must comply with BS6229 and BS8217 to produce a minimum gradient of 1:40 and maximum of 1:80. This allows the roof to shed water easily. To achieve this, nail wedge–shaped ‘furring pieces’ the same length as the joist, onto each joist. On top of this, nail 25mm thick plywood to provide the support for the covering.
Instead of timber, some flat garage roofs use concrete. A concrete garage roof uses steel RSJs or concrete lintels in place of timber joists. Standard concrete blocks fill the gaps between the joists. Next, a layer of screed covers the concrete structure to seal all joints and gaps. Only then is the surface ready for the waterproof covering.
There are other types of roof coverings available. A corrugated garage roof uses timber joists to provide the structure, followed by corrugated plastic or metal sheets for covering. A metal garage roof using corrugated iron used to be very common back in the day. But today, corrugated clear PVC or Polycarbonate sheets are more common.
Lastly, we’ll say a quick word about pitched garage roofs. It’s common for garages with pitched roofs to be detached and to have timber rafters covered in tiles or slates, similar to a domestic property. Having said that, corrugated iron is also a favourite covering, but isn’t as pretty. For this reason, pitched metal garage roofs tend to be used in commercial or agricultural settings rather than domestic.
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Additional Factors
As a general rule, large single, and double garages won’t have a pitched roof. If they did, the pitch should match and be the same as the house’s roof. Therefore, if the span between external walls is similar to your home’s, the garage roof will be about the same height as your home’s roof. This may look okay if you have a house and there’s a large distance between the two structures. But, if you own a bungalow or the two properties are close together, It might be difficult to tell the difference.
Generally, flat roofs have pros and cons, just like everything else.
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Benefits
- During winter months, the dark expanse of flat roof absorbs the sun’s warmth, which transfers to the inside of the building.
- If you wish to do maintenance, a flat roof is easier to stand and walk about on.
- A flat roof uses fewer materials and takes less time to build than a pitched roof. It’s therefore considerably cheaper.
- Ordinarily, space on the roof would be wasted. However, a suitably constructed flat roof can double as a garden, patio or communal outdoor living space.
Drawbacks
- Depending on the construction materials, its lifespan might be as little as 10 to 15 years.
- Drainage of rainwater and other debris from flat roofs is a problem. If the area isn’t regularly cleaned, the covering material might degrade faster than normal.
- Flat roofs need more maintenance than a pitched roof. So, consider the implications of this before choosing one.
- Due to the limited number of suitable covering materials, you have a very limited style range for your flat roof.
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Roof Building Regulations & Planning Permission
The UK Building Regulations and Planning requirements of flat and pitched roofs differ.
Flat roofs
Usually, repairs won’t need to comply with building regulations. However, if you are completely replacing the roof and incorporating integral insulation, you might need to upgrade the thermal element of the garage and reduce the amount of heat loss by using a thicker layer of insulation.
If you aren’t changing the overall height or shape of the roof, you shouldn’t need to apply for Planning Permission. Check with the Planning and Building Control Offices, in your local authority for more guidance.
Pitched roof
If you intend replacing the roof covering with a different material, for example, slates or tiles. Then, you must comply with Building Regulations regarding structural strength and stability. Furthermore, you must also comply with fire safety and energy efficiency requirements. Contact the Building Control Office for advice.
There are various Planning regulations regarding changes in appearance and height, so ask for guidance from your local Planning Department.
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British Standards Codes of Practice
A flat garage roof’s construction must comply with Codes of Practice specified in BS6229 and BS8217. These specify Codes of Practice for the construction of the roof.
A flat roof must have a minimum gradient of 1:40 and maximum of 1:80. This slope provides the optimum slope range so that rain sheds easily, carrying with it as much debris as possible.
They also specify the best way to allow water vapour to escape using breather membranes or a vapour control membrane.
Hiring A Roofer? – Questions to Ask
A garage refurbishment will cost a lot of money to do properly, so it makes sense to hire a suitably qualified tradesman to replace or renovate its roof. Here are a few of the most important questions to ask anyone you intend to hire.
- Has the roofer any references or personal recommendations he can supply? Follow these up and ask the customer about the job.
- Experience. Most roofers can install slates and tiles, but if you want a flat roof using one of the new technologies, then the roofer must be qualified and have training.
- Is the roofer a member of the National Federation of Roofing Contractors (NFRC)? Their website has a tool for finding members near you. They also have a code of practice that members follow
- Ask for a quote from at least three contractors. Make sure they visit and inspect the site to give a good comprehensive quotation. You should avoid ballpark figures over the phone, as they don’t take into account on-site problems.
- Remember, the cheapest quotation isn’t always the best. Either the roofer isn’t experienced and has forgotten some vital item. Or, he’s given you the basic price and expects to add more items onto the bill at the end. By the way, you can always expect some extras on a job like this. There might be other expenditure that doesn’t come to light until they remove the existing roof. For example, water–damaged plywood or rotten joists. However, a reputable tradesman will already know that and should make you aware of this right at the start.
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Garage Roof FAQ
How much does it cost to replace an asbestos garage roof?
Legally, you must not do this yourself. Asbestos must be removed and disposed of by HSE registered companies and local authority approved waste handlers. It is against the law to do otherwise. So, you will always pay the going rate for your area. As a rough guide, removing an asbestos garage roof will cost about £400 for a single garage and about £800 for a double garage. Remember, if you have asbestos garage roof sheets, you might have asbestos elsewhere. For example, removing asbestos insulation boards will start at about £1400.
What is the best material for a garage roof?
All flat roof coverings have their advantages and disadvantages, so it’s best to discuss this with a skilled professional roofer regarding your situation. However, EPDM rubber is probably the best long–lasting and most durable material.
What type of roof will last the longest?
This question could refer to the style of the roof or the roofing material. Fortunately for us, the answer is the same in both cases. Namely, “a pitched, timber structured roof with vapour barrier covered in slate or tiles”. This roof will significantly outperform any other roof type or material currently on the market.
Should I insulate my garage roof?
You can if you want to. But, garages aren’t usually designed to be airtight. So, you’ll have gaps around and under the garage door, and probably elsewhere too. And, all of them leading to the outside. So, the benefits of any insulation you install will be completely wasted.
How long does it take to replace a garage roof?
Provided there aren’t any other repairs, such as repairing or replacing structural timber joists or plywood garage roof panels, a standard single garage roof takes about 1 day to remove and replace.
Find A Local Roofer Near You
Ensuring you have a weathertight garage roof is essential if you want to use a garage to its fullest potential. Not only that but a sound garage will also add value to your home. Complete the form on this page and you’ll receive 2 or 3 quotes for the cost of replacing a garage roof, from qualified roofers local to you.
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