How Do You Convert A Flat Roof To A Pitched Garage

How Do You Convert A Flat Roof To A Pitched Garage?

A flat garage roof isn’t the best thing to have on a structure as it’s subject to pooling water and snow. 

Changing the garage to a pitched roof takes work but brings greater protection and more room in the garage. 

It’s not an easy job and requires at least two people, but the results are worthwhile, and you don’t need extensive knowledge of carpentry to do it. Are you getting frustrated by your clutter and garage organisation? Here at Garage Storage Solutions, we offer extensive professional organising and declutter service.

What Is A Pitched Roof?

What Is The Best Material For A Garage Roof

First and foremost, what do we mean when we say pitched roof? We’re talking about any top that has a peak. 

This is the type of roof you’ll see most often on residential homes here. Pitched roofs are what give you that triangular shape at the top of your home and create those tall attics on the inside. 

Pitched Roof Pros

As you can imagine, there are plenty of reasons most homeowners and business owners choose pitched roofs, especially considering pitched roofs are significantly more common than flat roofs. A few of the pros you can expect when you opt for a pitched top include:

Longer lifespan — the average asphalt shingle pitched roof has anywhere from 20 to 50 years, depending on what shingles and roofing material you choose. Other than a metal pitched roof, this is the longest-lasting roofing option. 

 Less Maintenance: Pitched roofs are designed to let precipitation like snow and rain slide right off. 

They’re built with a pitch to reduce the beating a roof takes and minimise the potential for leads as your roof begins to age. 

That design feature means that you’re going to experience far fewer maintenance requirements throughout the life of your pitched roof than you would with a flat roof. 

Pitched Roof Cons

The only real problem with a pitched roof is the initial upfront installation cost compared to a flat roof. 

In general, a pitched roof costs more to install because it will take longer and require more material than a flat roof. 

That said, as far as overall costs go, you’re still likely to pay less in the long run when you opt for a pitched roof. 

The other potential negative with a pitched roof is regarding aesthetics. If you’re designing a contemporary, modern building, a pitched top may not fit with the architectural style you’ve planned. 

In that case, a flat roof does make more sense to tie together the overall look of the building. 

What Is A Flat Roof?

As you might imagine, a flat roof is, well, dull. Although most commonly seen on commercial buildings and contemporary architecture, flat roofs aren’t completely flat. 

Most flat roofs are designed with a slight, almost undetectable slope that pushes any precipitation out toward the building’s gutter system. 

Flat Roof Pros

If you’re not sure whether a flat or a pitched roof is the right choice for your building, it’s important to consider two primary factors: cost and aesthetics. This is where the pros of a flat roof come in: 

Lower Upfront Cost: A flat roof is less expensive to install on a new building than a pitched roof. 

This is because it requires fewer materials and is structurally more simple. That means flat roofs can also be installed a bit more quickly, which is part of what makes them attractive for commercial buildings. 


More Cohesive Space: There’s a bit of controversy over whether a pitched roof or a flat roof provides a building with more space. Regardless, a flat roof does offer a more cohesive, usable space for an entire building. 

While a pitched roof might have a triangular attic, the entire top floor of a flat-roofed building will be the same size and shape as the lower floors. 

Again, this makes flat roofs a good choice for commercial use, as you can fit in more offices and storage space.

Modern Aesthetic — Clean, straight, and minimalist lines are the current trend for any building, whether it’s commercial or residential. If that’s the aesthetic you’re going for in your building project, then a flat roof can deliver. 

Flat Roof Cons

While flat roofs offer a more affordable upfront cost and can provide the aesthetics that many homeowners and business owners are looking for, they’re not always the most practical option. Here’s why:

Shorter Lifespan: A flat roof, on average, will last about ten years. That’s considerably less than the 20 year minimum of a pitched roof and means you’ll be spending quite a lot more on roofing over the decades if you’re planning to stay in the building long-term. 

Increased Maintenance: Because flat roofs are flat, they pose some structural concerns, especially for buildings in areas that experience a lot of rainfall and snow. 

For that reason, it’s recommended that you have your flat roof inspected at least once a year, if not more regularly, to ensure you don’t miss any big problems with your roof. 

Luckily, flat roofs are pretty easy to inspect because you can walk on them easily, so it won’t cost much to regularly get a roofer out to your building.

Greater Chance of Leaks: Again, the problem with flat roofs is that they’re flat. Even though most are designed with a slight slope, they’re not great at shedding a lot of rain or snow. 

As a result, rain and snow tend to build up or puddle at various spots on the roof, which often causes leaks as the water sits there for quite some time. For this reason, flat roofs tend to cost more overall than pitched roofs. 

Does The Flat Roof Have Significant Damage?

If the flat roof has become damaged, it can be for several reasons: Poor design, construction or maintenance. 

Typically, flat roofs are more likely to suffer worse water damage than pitched roofs, resulting in damage to the structure due to the strain placed on the walls.

At this point, you may be wondering whether it is best to replace a damaged flat roof with a pitched roof to stop water damage arising in the future.

A conversion to a pitched roof may not cost any more than a flat roof replacement making it a viable option for many people.

New developments in building materials such as low pitch roof tiles have made extensions increasingly simple, cost-effective, and attractive.

Will A Pitched Roof Last Longer?

In general, pitched roofs are thought to last longer than flat roofs when it comes to longevity. However, it depends on the artistry of your contractors and the quality of the materials for how durable your roof will be.

After particularly bad weather, it’s important to remove any debris that builds up on a roof to stop damage and to weigh down the roof.

Choosing a durable material and sufficient water run-off capability is key to ensuring the roof stands the test of time.

Do You Need To Insulate The Garage?

Converting a garage into a family room is a popular choice for many people who require extra space and are looking to increase the value of their home.

If you consider a conversion, a pitched roof may be a better option than a flat one as you can more easily insulate and ventilate it.

Garages tend to be cold and have little to no insulation because a flat roof does not allow much space for insulation.

A garage usually doesn’t need insulation – unless it becomes a habitable room, at which point, the height of the roof will become important.

The material you choose for insulation depends on the pitch of the roof you opt for. Aim for a good balance between ventilation and insulation if you are converting your garage into a room.

Is Planning Permission Required?

Converting a flat garage roof to a pitched top is a relatively simple job for professional roofing contractors. 

However, you will likely need to apply for planning permission as it is not a like-for-like replacement.

This should be a straightforward process, especially if it is a low pitch roof. However, if you’re planning to make more complex structural alterations, it may be best to contact the local planning authority for their advice.

Remove Flat Roof

Before you can properly measure your pitched roof, you need to remove the old flat roof. Take off any shingles and covering, followed by the plywood of the top and discard. Inspect the structure that remains for any rot in the wood. 

If all is fine, then you can proceed. Pay attention to the spacing of the joists and be certain they can hold weight. Garage Storage Solutions’ smart wall storage system (hooks, racks, baskets and shelves) can be used in unlimited configurations and be adjusted over time as your requirements change. They are making it a perfect investment for your garage.


The simplest way to replace the flat garage roof with a pitched roof is to use prefabricated roof trusses. 

Please measure the width of the garage to know how long you need them to be, and count how many joists there are along the length. It will help if you put a truss over every second joist.

Start by putting a truss at the front end of the garage. You’ll need to connect it to the wall structure and joists with baseplates that have been bolted in place. After this, put another roof truss on two beams away, using the same method. 

Connect the two at the ridge for strength. Continue to add trusses until you reach the other end of the garage. If you need to leave the work overnight, cover the entire roof area with tarps.


Before covering the roof with plywood, you will need to measure and cut plywood for the gable ends. Then, attach the screws to the sides of the roof trusses. 

Once you’ve done this, cover the roof with plywood, cutting the sheets where needed and hammering them into place on the roof trusses. At this point, your flat garage roof has taken on an entirely new shape.

Roof Covering

With the pitched roof in place, now you need to cover it. Start with tar paper, running it in rolls along the length of the garage and working up toward the peak. 

Making sure it’s flat, nail in place. This will create waterproofing for the plywood. Over this, you’ll need to place the shingles, again working up toward the peak and finishing with ridge shingles to ensure water doesn’t enter from the top.

Gable Ends

The pitched roof is now covered, but the raised gable ends are still bare plywood. So to finish them off, you’ll need to protect them in the same way that the rest of the garage is covered, typically with siding. 

This is easily installed directly over plywood. Then, complete by priming and painting, the siding and the flat garage roof has been transformed.

Pros And Cons Of Converting A Flat Roof To A Pitched Roof

How Do You Convert A Flat Roof To A Pitched Garage2

The Process Of Changing The Pitch Of Your Roof

If you own a building with a flat roof, your contractor will first consult a structural engineer to make sure your structure can handle the conversion.

Pitched roofs are usually much heavier than flat roofs, so an easy replacement may not always be possible.

If it is determined that your building can support a pitched roof, the next step will be to remove all of your roofing materials and the main roofing structure.

Pitched roofs require more workforce and time to install, especially when making a major structural conversion. 

A pitched roof will require new roof trusses and supports. In addition, any damaged wood will need to be removed and replaced.

A contractor may choose to construct new trusses on the spot or have them delivered pre-assembled once he has taken measurements.

Part of the process involved in changing the pitch of your roof will be calculating the cost of all necessary materials. 

You will also choose your new roofing material as this will be completely different from the materials used to cover a flat roof.

Pros And Cons: Flat Roof And Pitched Roof

There are advantages and disadvantages to each type of roof:


Most people want to know first how much each type of roof will cost. There is no question that a flat roof is cheaper to install. 

A pitched roof is more expensive. It is a significant renovation if you are converting from flat to pitched.

However, flat roofs require much more aggressive and consistent maintenance than a pitched roof. Flat roofs also don’t last as long.

Depending on the climate, your flat roof will only last between 15 and 30 years if well-maintained. 

If you used long-lasting materials on your pitched roof, you could expect it to last much longer.

When making this decision, keep in mind both your short-term costs and long-term costs.


As mentioned above, the maintenance needed for each type of roof can differ quite a bit.

Flat roofs are more susceptible to damage if not repaired right away. Any ponding, debris or wind damage must be addressed as soon as possible, or you’re looking at significant structural damage.

Of course, a pitched roof needs maintenance as well. However, since flat roofs tend to become damaged more easily, you need to keep an eye on your flat top regularly.


Style can be such a personal decision. However, sometimes there are legitimate reasons either to change your roof’s style or to keep it as is.

If you own a modern home designed with a flat roof, you should keep in mind whether you are damaging its resale value if you change the style of the house by adding a sloped roof.

In that case, it might be in your best interest to keep your flat roof.

The same goes for a townhouse or apartment building that was designed with a rooftop balcony. 

Maybe you are tired of the maintenance associated with a flat roof, but consider the valuable rooftop real estate you may lose if you convert.

However, in many cases, the style of your building can be enhanced by adding a pitched roof.

Pitched roofs shed water much more easily, and they last much longer. They also add an essential structural presence to your building.

If you own a warehouse you want to turn into a commercial retail space, for instance or a church building, you may want to consider adding a pitched roof as a way to make the building more inviting or grander.

Pitched roofs are an excellent way to add square footage on the inside of your building as well.


You don’t need to be an expert or have a degree in architecture, but you want to make sure that the roof is structurally sound and won’t cave into your garage. 

If it was just for storage purposes, then a flat roof may be sufficient enough. However, if you plan on living there as well, then go with a pitched one so that insulation can protect you from leaks and keep your home at comfortable temperatures year-round! Garage storage wall hooks should form part of any garage makeover as they provide a clean and really easy way to lift anything from your garage floor and have it accessible via your garage wall.

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