Garages are like gold dust when you’re househunting. You can store the kids’ bicycles, your DIY tools, and have a home gym. You can even keep your car in it.
Unfortunately, when you find a garage, the first thing to degrade is its roof. Often, garages had flat-roofs and were covered with asbestos or roofing-felt. We no longer use asbestos, and roofing-felt garages leak after a few years. But, it’s no problem to replace.
The cost of a new garage roof replacement starts at £75/m2 or £1100 with roofing-felt. Alternatively, a fibreglass flat-roof costs £125/m2 or £1800 for a single car garage. Furthermore, it won’t take long for a contractor to provide a new garage roof, perhaps a day or so.
Replacing your garage roof in the UK is pretty straightforward, and you can get estimates from most building, flat-roofing or specialist garage roofing companies. Alternatively, use the form on this page, and we’ll ensure you receive some reasonable quotations.
How Much Does A Garage Roof Replacement Cost?*
If you want to calculate a garage roof replacement cost, use the table below. Although the sizes might not be the same as yours, they allow you to compare and find an approximate price. There is no official size for a garage in the UK. A garage is as large as you want it. However, British architects suggest that the minimum size for a single garage should be 3m wide by 5m long. In comparison, a double garage should have minimum dimensions of 5.5m wide by 5m long. Therefore, we’ll use these dimensions in the absence of any others.
|Garage Size||Material||Estimated Cost (per m2)||Estimated Cost (Total)|
*We compiled these estimated figures from various resources. Every garage is unique, so use them when calculating benchmark prices while researching garage roofing contractors. Furthermore, the estimated prices include materials and labour costs. But, disregard replacement roof timbers, such as rafters, furring pieces and 25mm thick plywood, or other types of structural roofing.
Unfortunately, when changing a garage roof, you must include other costs in your budget. Depending on your existing garage roof, you may not need all these in your project.
- Scaffolding – allows access to the roof. Prices range from £30-£40/m2.
- Waste removal – Removal of old roofing material costs £110 for a small skip plus £130/tonne for landfill waste and £50 for a road permit.
Garage Roof Replacement, Price Factors
Several factors affect the costs involved when reroofing a garage.
Labour charges vary around the country. Typically, costs in London and Southeastern England can be up to 20% higher than charges elsewhere in the country.
Many old garages use corrugated asbestos-cement panels as a roof covering. These become brittle and easily break, after which the garage suffers from a leaking roof. You must use a licenced asbestos removal company to remove and dispose this safely. Asbestos removal companies charge £8-£50/m2 depending on type and amount.
Sometimes, it’s not only the waterproof covering that needs replacing. In this case, you must repair or replace the structural roof timbers, such as rafters and joists, before further work. Moreover, the dimensions of structural timber depend on many factors. Therefore, these guidance notes help with selection.
Professionals always cover a flat roof’s structural timbers with external plywood or Stirling Board as a base for the waterproofing material. Typically, exterior grade plywood sheets measure 24mm x 610mm x 610mm and cost around £30/sheet.
Choose one of four waterproofing methods. However, some are better than others:
- Cold bitumen felt – Cover the plywood in bitumen paint, followed by nailed felt. This is the cheapest to install and can be done as a DIY project. However, it’s probably the least durable of the lot. Bitumen paint costs from £12-£25/5L tin, and felt costs from £15-£60/10mx1m roll.
- Hot bitumen felt – Pour hot melted bitumen onto the roof and stick the roofing felt to it. Once the bitumen cools, the seal is complete. This is the cheapest durable roof at £75/m2. But, as it needs specialist tools, a contractor should install it.
- EPDM rubber – This material is very lightweight, flexible and durable. Moreover, unlike hot bitumen, you don’t need to apply heat, only adhesive. This costs about £90/m2 and requires a specialist company.
- GRP fibreglass – This is lightweight and durable, doesn’t need heat to install and is an attractive unbroken surface, unlike the others. However, it isn’t flexible, so it might have problems if the roof flexes. This costs about £125/m2 and needs a specialist installation company.
Types of Garage Roofing
Before continuing, we should look at the various roof types and coverings:
Regardless of what the name suggests, this roof isn’t flat!
On top of horizontal joists, nail wedge-shaped “furring pieces” along their entire length, producing sloped supports, onto which we screw 24mm thick exterior plywood. Alternatively, some flat roofs use concrete lintels or RSJs to substitute the timber. Standard sized concrete blocks infill the spaces between the lintels, and finally, a mortar screed seals all gaps and joints.
Finally, a waterproof layer covers the roof construction. This can be the felt, fibreglass or EPDM rubber coverings mentioned earlier. Alternatively, use corrugated iron or plastic sheets. Iron was standard a couple of decades ago, but corrugated PVC or polycarbonate sheets are more common now.
Many detached domestic garages have pitched roofs, comprising structural timber rafters or timber roof trusses. These are covered in plywood for stability, followed by a waterproof membrane and tiles or slates.
If the building is commercial or agricultural, the roof covering is often corrugated iron. Although iron is cheaper than tiles, it isn’t pretty, so try not to use this material in a domestic setting.
EPDM is a flexible rubber sheet glued to the plywood.
- Rubber is flexible and waterproof. Therefore, it’s a good roofing material if the adhesive stays intact.
- It’s easy to repair with patches, even if you do it yourself.
- EPDM reflects heat and insulates against the cold. Therefore, it protects the garage interior all year round.
- Some EPDM roofing is made from recycled materials. Therefore, the product might be sustainable.
- It comes in various sized sheets, from 1m-10m x 1.4m, or cut to size. Therefore, you can minimise the number of seams.
- Flexible, so it moves as the building settles or flexes.
- Not suitable for DIY. It must be installed by a skilled professional.
- Sealing around pipes, HVAC units, and chimneys in the roof threatens the roof’s integrity and will likely cause leaks.
- Although it’s easy to repair, it’s also damaged easily from foot traffic, falling branches etc.
- It’s not easy to find the location of leaks as the smallest split allows water to ingress.
GRP fibreglass is an epoxy slurry reinforced with flexible glass matting.
- GRP is durable and, when installed correctly, lasts over 25 years.
- GRP has no joints when properly installed, so it is entirely waterproof.
- Repairs are simple for a professional. But, some repairs can be DIY.
- You can choose from a wide range of colours for the final finish.
- GRP resists damage from footfall, vandalism, fallen branches, and other causes.
- More expensive than the other roofing materials.
- Not recommended for large roof spans as it can have significant expansion/contraction rates.
- Only install GRP during ideal weather conditions, i.e. dry.
- Only professionals can install GRP roofs.
These are corrugated Panels made from galvanised steel.
- Quicker to install than other roofing materials.
- Corrugated iron can last a lifetime if maintained correctly.
- Paint them in colours to suit your décor.
- Heavy to lift into position.
- Conducts heat so that the garage will be hot in summer and cold in winter.
- Difficult to cut with hand tools.
- There are several colours available, and the rough texture looks attractive.
- Use on flat or pitched roofs.
- Low contraction and expansion rates so can be used on any sized roof.
- Compared to other roofing solutions, bitumen felt is the cheapest.
- Easy to repair small patches.
- Cheapest flat roofing material available.
- Although you can DIY cold bitumen felt roofing, it’s better to use a professional to avoid leaks. In comparison, hot bitumen felt must be done by a roofer because of the specialist tools.
- Felt has an easily damaged surface, especially from ladders and footfall.
- In summer, the bitumen becomes soft and sticky. Therefore, avoid footfall.
Hiring A Roofing Company: Top Tips
Reroofing your garage is expensive, so you must ensure the professional roofer knows what to do. Here are a few essential questions to ask a prospective contractor.
- Have they any references you can follow up on? It’s the finished installation that matters. Therefore, you want to know that the roof looks good, is free from leaks and is correctly installed.
- Some of the new roofing technologies need specialist equipment and knowledge. Therefore, ensure the contractor has relevant training and follows the industry codes of practice.
- Is the contractor a member of a relevant trade association? The National Federation of Roofing Contractors (NFRC) and The Liquid Roofing and Waterproofing Association (LRWA) are good organisations to look out for. All trade associations insist their members follow their code of practice and work professionally.
- Search the Competent Person Register for local authority approved contractors.
- Ask for at least three quotes before you decide on the contractor. Insist they visit your property to inspect the existing roof. Therefore, avoid quotes over the phone without seeing the job.
- Don’t always go for the cheapest quote. Try to choose one somewhere in the middle.
Garage Roof Replacement Process (Step by Step)
Installing a GRP fibreglass, EPDM rubber, or hot bitumen felt roofing are all specialist jobs. Therefore, leave it up to the professionals. Instead, we’ll consider installing the wooden structural timbers and boards beneath the waterproof layer, which you can do as DIY.
You already have a garage, so you won’t need planning permission unless you alter it significantly. While you’re fixing the roof, you might be tempted to build the garage higher, wider or longer. However, you might get into trouble if you do. Therefore, ensure you know the law, which we cover elsewhere in this guide.
Inspect structural timber
- Strip the existing roof covering and dispose of it according to local and national waste disposal regulations.
- Inspect the roof timbers and plywood covering for areas of rot. If they’re okay, you can leave them in place. Otherwise, repair or replace them as necessary.
- Remove and replace rotten fascia boards.
Clean existing surfaces
- Ensure all plywood surfaces are clean and rot free.
- Fix triangular cross-section timber upstand along three roof sides to channel rainwater. But, leave the lowest edge open for rainwater runoff.
This step you should leave to the professionals.
Cover the plywood or Stirling board with the waterproof covering, ensuring they mould the waterproofing up and over the triangular section timber along the three edges. This channels the rainwater to the guttering on the fourth edge. Cover the fascia’s top edge with the waterproof covering to prevent water ingress.
UK Garage Roofing Requirements (Compliance)
You need to follow Building Regulations if your garage is as follows:
- Contains sleeping areas.
- It is over 4m in height.
- It is less than 1m from a boundary.
- Has a floor area of more than 30m2.
- It is structurally connected to your house or your neighbours.
At present, a Planning Permission application costs £206. You pay the fee on submission when:
- The maximum eaves height exceeds 2.5m.
- The overall height exceeds 4m for a roof with two slopes and a ridge. Or, 3m for any other type of roof.
- It is higher than 2.5m when within 2m of a house boundary.
- You want raised balconies or platforms.
- You extend the garage forward of the house’s main front elevation.
There are other restraints, so check with your local authority before you start altering your garage’s dimensions.
British Standards Codes of Practice
A garage’s flat roof’s construction must comply with BS 6229 and BS 8217. These standards contain specific Codes of Practice:
- A flat roof’s slope must be between 1:40 and 1:80. This gradient provides the best pitch for shedding rainwater and debris.
- The standard specifies how to shed water vapour using breather or vapour control membranes.
DIY vs Hiring a Pro?
Although an amateur can do minor repair jobs on flat garage roofs, you should leave the construction to a professional. This includes structural timber, boards, furring pieces and the waterproof membrane.
The materials involved in building a flat roof are expensive, and you run the risk wasting your time and money if you make a mistake with DIY. After the first rainstorm, there’s nothing worse than water dripping through a leak you can’t find. Therefore, always use a professional. You can search on the Competent Person Register for someone approved by your local authority.
Do you need planning permission to change a garage roof?
Suppose you intend to change the garage’s dimensions, function or appearance. Then, you should contact your local authority for advice. There is a list of the main restrictions elsewhere in this guide, but others might apply.
Which is the better roof, flat or pitched?
The primary purpose of a roof is to protect the interior from rain. In this case, a pitched roof with a vapour barrier and slates or tiles will outperform any other.
What is the best material for a garage roof?
All the available roofing materials have their advantages and disadvantages. Therefore, discuss this with a roofing professional skilled in using all the waterproofing methods discussed in this guide. Generally, however, GRP Fibreglass combines good looks and durability and is the best material overall.
What is the cheapest way to replace a roof?
The cheapest way is to cover a flat garage roof with cold bitumen paint, and roofing felt. Furthermore, if you like to DIY, you can even do this yourself. However, this isn’t the best method, it won’t last very long, and we recommend against it.
Find Local Roofers
Finding local garage roof replacement specialists can be difficult if you aren’t sure what to do. There are different waterproofing methods, and not all roofing companies specialise in them. Therefore, you might find a company that steers you towards what they can do rather than what’s best in your situation.
Complete the form on this page, and we’ll pass your details to the right roofing company. Then, you’ll receive up to four quotes so you can choose the right one for you.