I spent 40 years as an architectural technologist, and in that time, I’ve seen the best and worst techniques for roofing.
How much for a pitched roof on a garage may seem like a simple question, but trust me, there are many variables to consider.
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How Much Do Materials and Labour Cost in 2023?
As a ballpark figure, it will cost around £5,000 to put a pitched roof on a single garage. This estimate depends on many factors, which I’ll go into below.
How Long Does it Take?
The whole job can be completed on-site in a matter of days by a professional, but if you’re looking to do all or much of it yourself, be prepared to plan and do whatever’s needed to make things run smoothly.
Why Do You Want to Change the Roof?
People decide to change their garage roof for a variety of reasons. Here are the most common reasons:
Housing your car in a garage has many advantages, from lowering your car insurance to protecting it from the elements. However, many people now see the benefit of extra storage space.
Old Roof Needs Replacing
Older flat roofs are notorious for leaking and causing the substrate to rot. This risk is not a big problem in modern flat roofs, but issues still arise.
The Felt gets brittle and cracks. You can patch up joints, but eventually, you must succumb to the inevitable.
It’s a subjective matter, but pitched roofs can improve the appearance of your property and even add value to your home.
Pitched Roofs Last Longer
Pitched roofs outlive flat roofs, but how long they outlive them depends on the materials.
Types of Roof Covering Materials
Below are the main types of garage roofing materials.
Clay Tiled Roof
Traditionally, the most popular choice due to the range in colours and styles. However, clay tiles are prone to crack or work loose, especially if you walk over them for maintenance.
More appropriate in rural areas, slate is excellent roofing material. However, slate is a specialist material best left to professionals who know how to fix it.
Concrete Interlocking Tiles
Concrete interlocking tiles have been around for over 50 years as a modern alternative to clay or slate. Like clay, they come in various colours and profiles to resemble pantiles or slate.
Using profiled metal or plastic sheeting is the quickest and easiest way to cover a pitched roof.
Given the number of options, it doesn’t have to look cheap, but some consider it “industrialised”.
Choosing a Garage Roof Covering — Key Factors
Below are the key factors to consider when picking the best type of roof covering for your circumstances.
Pitched Roof Cost per m2
If cost is the driving factor, profiled sheeting is the most economical. However, concrete interlocking tiles provide an excellent solution at a reasonable price for most situations.
Local Choice (Surrounding Area)
It’s always nice to blend in with your surroundings, but don’t think you have to for planning purposes. Regulations have eased in recent years (see below).
Pitch of Roof
If you’re working to a low pitch of around 15°, you must consider interlocking tiles because they have grooves that stop water from blowing up and into the garage.
Garage Roof Ideas — Types of Roof Structure
Below are the roofing structures to consider when planning your new garage roof.
Full Gabled Trusses
The typical A-shaped roof with a flat frontage is the most common type of roof structure. Therefore, it has the advantage of repetition in design and is more economical to fabricate.
Opt for a hipped roof if it matches your house. However, expect a loss of storage space and expect to pay around 20% extra for labour and materials.
Triangular or Monopitch Trusses for Lean-to Roofs
Like a full-gabled truss, triangular trusses have a single pitch running away from the house.
Loose Rafters and Braces
Constructing the roof using loose timbers rather than prefabricated trusses is possible, and the DIY market favours this approach. However, you must work out the timber sizes to cover the load and span.
Consult Building Regulations for more advice on this (see above).
Lean-to roofs often encounter obstacles that complicate fixing the new pitched roof to the existing wall.
Soil Vent Pipes and Rainwater Pipes
All pipes need proper flashing around them to avoid water penetration into the garage below.
Windows in the Main Wall
Windows present a problem because the cill height is often lower than the top of the new roof, requiring special trimming that may be beyond the average DIY enthusiast.
You may find you can’t fit the barge board and gutter if you’re close to a boundary. In these circumstances, ask a building surveyor for advice.
Similar to pipes, boiler flues must be flashed. However, this is a little trickier due to potential heating problems.
You must also check the height of the flue against the new roof to ensure there’s enough draw to disperse the fumes.
Pitched Roof Garage Conversion — Getting Permission
There are two things to consider — Building Regulations and Planning.
Building Regulations — Weight of Materials
The Building Regulations provide all the measurements you need to determine the size of rafters for a given pitch and weight.
Planning — Height and Appearance
This requirement mainly affects conservation areas and listed buildings. I.e. you don’t need Planning Permission in most situations, but it’s advisable to consult your local planning office before commencing.
Is the Structure Below Adequate?
Below are the key factors to consider when evaluating your supporting structure. If in doubt, speak with a structural engineer.
Size and Thickness of Wall
Many garages are built using single-leaf (102mm) brickwork with thicker piers at the corners and mid-span. This construction might not be strong enough to take the extra weight of the new timbers and roof covering.
Not only can the extra load stress the brickwork, but it can also cause the foundation to collapse if they’re not deep enough.
Many garages are built off a concrete raft, so you’ll need professional help to determine this.
Existing Roof Joists
In some situations, it may be possible to use the existing flat roof joists as the basis for your new roof. They’re often strong enough because they’re designed to take wind and snow loads. However, you must ensure there is no rot or beetle attack.
DIY or Trade?
Here are some factors to consider when making this critical decision:
How Much Can You Do Yourself?
Even if you decide to use a tradesperson or construction company, there are still things you can do yourself to help keep costs down.
Strip Off Existing Materials
Doing this job yourself can save a lot of time and money. The less time your contractor spends on-site, the better for your wallet.
Hire a Skip to Dispose of Waste
Most professionals have contacts with waste-removal companies and can negotiate a better rate. So only use this option if you decide to strip the roof yourself.
Look Out for Asbestos
Asbestos remains the biggest killer in the construction industry, despite being banned from use in 1999. Those who suffer from its past use are mostly maintenance workers who’ve handled asbestos for years.
Still, if you’re removing asbestos material, you must take precautions such as PPE, double bagging, and disposal to a registered site.
Not everything that looks like asbestos is asbestos. Many asbestos-free products were used in the 1990s, and there is no visible difference to the untrained eye. My advice – let the professionals test it and deal with it appropriately.
Finding Qualified Contractors
Follow the tips below when looking for top professionals in your area.
Call the people offered as referees and, if you can, go and take a look at what the contractor did.
Level of Experience
Do they have experience in your desired roof construction? Many contractors have their way of doing things and say their method is the best. Confirm their practices match industry standards.
Do they erect scaffolding? Scaffolding can cost between £250-£500 to erect, and there may be daily hiring costs of around £50, so some contractors omit this to win the job.
Omitting scaffold is a bad idea. Scaffolding is not only there to load materials onto the roof and to use as a work platform; it also protects builders.
I recall having a re-roof on a single-story kitchen extension when the roofer told me he’d fallen off much higher roofs than mine (several times, I’d say, from his lack of teeth and cranial indentations). These anecdotes serve little to provide confidence in the contractor.
Being professional is more than just wearing a company t-shirt; it’s about how they do their work. For example, does the contractor clean up every day? Are they courteous and on time?
A professional also provides regular updates, including any potential changes in cost or time. Nobody wants surprises at the end of the job.
Always get three quotes in writing and ensure they include the following information:
Many tradespeople offer significant discounts when they’re not registered for VAT. These discounts may be tempting, but you should avoid such offers because it indicates the company has little legal footing, which may cost you if things go wrong.
Also, don’t be tempted by cash-in-hand offers; this could be illegal.
Ask how long the work is guaranteed and whether there are any limitations.
All good professionals carry insurance to cover damage to your property and injury to themselves and their employees.
Many of the materials come with a warranty of some sort, so make sure the warranty and proof of purchase end up with you.
Always agree on terms at the outset and avoid upfront payment. A good contractor has enough cash flow to cover a job this size.
Some contractors offer credit card payments, but this often comes with a premium.
Contractors are great at telling you what they’re including but reluctant to say what’s NOT part of the job. Ensure you get a complete list of inclusions and exclusions so you can budget accordingly.
Don’t fancy doing this job yourself? Find top-rated builders in your area by clicking the button below:
After reading this guide, you should now understand the pros & cons of various roofing materials and methods.
You should also understand the costs of each option and whether you should undertake this job yourself or hire a professional.
Pro Tip: If you’re still wondering whether you can replace your flat garage roof with a pitched roof, I urge you to watch the video below for inspiration:
If you don’t fancy doing this job yourself, I highly recommend using Rated People to find a top-rated professional in your local area.