Building Rooftop Deck Over Garage? (9 Important Questions to Ask!) is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to . The website is also an affiliate of a few other brands.

Building a rooftop deck over garage is a very exciting prospect! Especially if you have a small backyard but love entertaining. However, before you jump at the idea you will do well to ask 9 important questions.

Building a rooftop deck garage is not for everyone. But is it for you? Can you build a rooftop deck over garage?

You certainly can build a rooftop deck over garage, but ask yourself these 9 important questions first. Even if you do not tick all the boxes, there may be a workaround.

If your home and garage are still in the design stage then it makes incorporating a rooftop deck garage in the plans relatively simple. However, things can be a lot more challenging in case of an existing garage.

Here are the questions that you need to ask.

1. Does your garage have a flat roof? A rooftop deck is possible on both flat and pitched roofs, but the cost may vary based on the pitch. A low pitch is easier and cheaper to build on.
2. Is your garage roof structurally sound? Ensure your garage can handle the additional load from the rooftop deck, including people and furniture. Get an assessment done by a certified structural engineer.
3. Do you need a permit to build the deck? Most certainly. Check local building codes and obtain the necessary permits before starting the project.
4. How will you access the rooftop deck? Access depends on the floor plan; stairs may be required. Exterior staircases need adequate lighting for safety.
5. Do you get a lot of snow in winter? Rooftop decks may not be ideal for heavy snow areas as it limits use and can lead to overloading issues.
6. What about waterproofing & drainage? Proper waterproofing and drainage prevent damage and accidents caused by water pooling on the deck.
7. What about utilities like water and electricity? Check utility lines and follow regulations to ensure safety and functionality of the deck.
8. What type of materials should you use? Choose lightweight, durable materials like synthetic decking (engineered wood or PVC) for rooftop decks.
9. How much will it cost to build rooftop deck over garage? Plan a realistic budget, including permits and fees. Hire an experienced contractor with a detailed contract outlining project scope and payment terms.

Building a rooftop deck over a garage is an investment, but an investment that will not only give you many hours of happiness but will also increase the value of your home. 

Rooftop Deck Over Your Garage

So let me explain in more detail why asking the 9 questions is important and how they will impact your decision to build a rooftop deck over garage.

1. To Build a Rooftop Deck over Garage, is a Flat Roof Necessary?

This may sound like a “no brainer”. Of course you need a flat roof. 

However, you will be able to build a rooftop deck even on a garage with a pitched roof. Your cost of getting a flat rooftop deck over a garage with a pitched roof will depend on the pitch of the roof. 

A low pitch will make it easier and therefore cheaper to put up the rooftop deck. Building a rooftop deck over a very high pitch garage roof may not make much sense.

Actually, if you see a fair amount of rain and even mild snow, a pitched roof may become an advantage. The rain water or the snowmelt will flow through the gaps in the deck floor, on to the pitched garage roof and into the storm water drain system.

2. Is the Existing Construction Structurally Sound for a Rooftop Deck over Garage?

You may be tempted to ignore checking out the structural integrity of the garage roof. How much load can a simple rooftop deck add? 

Well, quite a bit actually!

Of course the decking and the deck framing will be the primary source of the additional load. Then there will be deck furniture. 

You may want to have a few planters around for ambience (or to grow herbs). You will probably want a barbeque and maybe a bar too. 

And do not forget the weight of the people. You most certainly will invite guests to your amazing rooftop deck. 

It all adds up!

You will need a certified structural engineer to check the load bearing capacity of the garage roof. He may give you the green signal or suggest modifications. 

Either way you will definitely need to submit his report to the local building authorities.

3. Does a Rooftop Deck over Garage need a Permit?

Chapter 15 of the 2018 International Building Code (IBC) provides minimum requirements for the design and construction of roof assemblies and rooftop structures. Rooftop Deck and associated structures fall in its purview.

IBC covers aspects like

  1. Drainage (Section 1502)
  2. Weather Protection (Section 1503)
  3. Fire Classification (Section 1505)
  4. Insulation (Section 1508)

Local building authorities, generally speaking, follow the guidelines laid down by IBC. If anything, they may have their own, stricter, regulations. So you must definitely check with them before embarking on your project.

A permit may or may not be required, but the authorities would like to get some documentation on the construction plans and type of materials that will be used.

The Homeowner’s Association (HOA) of your area may have their own rules & regulations. HOA are often quite concerned about issues  pertaining to privacy, safety and visual compliance with the neighborhood.

4. How Will You Access Your Rooftop Deck Over Garage?

This is an important question. You should not even think of using some makeshift arrangement like a ladder. Even a spiral staircase should be ruled out of consideration.

You are spending a good amount of money for adding some value to your lifestyle. Do not go “cheap” on the access.

Access to the Rooftop Deck Over an Attached Garage.

This could be rather easy or a bit complicated. It really depends on the floor plan of the 2nd floor of your house. 


It would be just fantastic if a common area such as a living room, a dining room or even a hallway adjoins the Rooftop that you are planning to build. 

In this case you could have a simple door or more grandiose French Windows as the way to access the Deck.

PROS: Easy Access, Easy Construction, Quick move back into the house if the weather changes.

CONS: Your guests will need to go through your house before they can get to the Deck.


Another option would be to build a staircase, along one of the wall, inside or outside the garage, leading to the rooftop deck over the garage. If the staircase is outside, be sure to provide adequate lighting for safety!

Access to the Rooftop Deck Over a Detached Garage.

In this case you just have one option. It is the same as Option 2 from above.

5. Rooftop Deck Over Garage – Can it Handle Heavy Snow?

To be honest, a rooftop deck over garage is not a great idea for folks who see heavy snow for several weeks in a year. 

Your Use of the Rooftop Deck will be Limited

The more time your rooftop deck is covered in snow, the less time you get to enjoy it. Would you spend a ton of money on something that you do not get to use. I would guess not.

Snow is Heavy and will Overload the Rooftop Deck

Snow is heavy. Of course you know that, especially when you have to shovel the driveway at times. 12” of fresh snow weighs 5 pounds per square feet (psf). As it settles down and freezes further, the weight keeps going up.

40″ of packed snow could weigh 40 pounds per square feet (psf). That is 20,000 pounds of snow on a 500 square feet rooftop deck over a standard 2 car garage.

According to the blog post “Residential PSF Deck Requirements” by

  1. For a residential deck, the code requires it be designed to support a minimum 40-psf live load. 
  2. The live load is the external force applied to a deck due to the activities of its use. 
  3. People, furniture and any other movable, physical objects on the deck are covered under live load.
  4. In regions with heavy snowfall, the snow load may exceed the 40-psf live load.

Snow does not clear easily from flat structures. It keeps piling up and keeps getting heavier.

So in regions with frequent and heavy snowfall a rooftop deck over the garage will be hazardous.  This is the reason house roofs are steep in such zones. You want the snow slipping off the roof, even with a slight melt.

6. What About Waterproofing and Drainage?

A rooftop deck over garage presents several challenges when it comes to waterproofing and drainage. 

To prevent water damage and leaks, it’s essential to assess the waterproofing capabilities of your garage’s roof. Make sure that the garage roof is inspected and repaired before installing the rooftop deck.

Special attention needs to be given to waterproofing the roof and ensuring that the drainage arrangements are adequate an accessible.

Proper waterproofing of either the roof or the deck will protect the structure and extend the lifespan of the deck. Additionally, plan and install an effective drainage system to ensure rainwater doesn’t pool on the deck.

7. What About Utilities like Water and Electricity?

Before you start building your rooftop deck over garage, identify any utility lines and service connections on the garage roof. It’s crucial to comply with regulations regarding rooftop structures near utility lines to avoid hazards or disruptions. 

You will also need utilities such as electricity and water on the deck, unless you plan to use the deck for just keeping a couple of garden chairs to sit in.

Arranging for electricity will be relatively easy as you can draw from the main panel in the house or the sub-panel in the garage. In any case, avoid loose wires or extension cables. 

Instead install proper electrical wiring with sockets along the deck perimeter. Use this electrical wiring to install permanent light fixtures that are UL rated for wet conditions.
Water supply will be a lot more difficult. However, there are many benefits to going ahead with it. At the very least you can use the water source to water the plants in the planters and clean the deck occasionally. 

8. What are the Best Materials for a Rooftop Deck over Garage?

In terms of construction the rooftop deck is pretty similar to a deck in the yard. But there are a few key differences to keep in mind.

Load per Square Foot

Obviously the load per square foot plays a far more important role in the case of a rooftop deck as compared to a deck at ground level. Every pound matters so you have to choose your materials very carefully.

Deck Framing

A rooftop deck on top of the garage still requires framing, on which the decking can “float”

On a solid flat garage roof you will need to prepare a substructure (aka sleeper system). The Decking will be laid out on this sleeper system. The sleeper system is very similar to the framing that you would do for a ground level deck.

The sleepers are basically 2X6 wood studs laid out 16” apart on a frame. You should of course be using “pressure treated” studs.

High performance extruded aluminum or wood plastic composites are gaining acceptance as joists for rooftop decks. The advantages are that they :

  • Light Weight
  • Do not Rust or Rot
  • Are Mold & Mildew Resistant
  • Are Pest Resistant
  • Are Fire Resistant


Traditionally decking is wood. Wood is not recommended as decking for rooftop decks because of higher weight, low fire resistance and poor durability.

Synthetic decking is a popular choice for a rooftop deck. Material options include engineered wood and PVC. These are lightweight and easy to maintain.

9. How Much Will Building a Rooftop Deck Over Garage Cost?

Building a rooftop deck over garage is an exciting project, but it’s crucial to understand the associated costs. The actual cost will depend on a range of factors. Here’s what you need to consider:

Design and Layout: 

Plan the deck’s design, purpose, and integration with your home’s architecture. 

A well-thought-out design can optimize space, enhance aesthetics, while keeping costs low.

Durable Materials: 

Choose high-quality, durable materials and finishes that can withstand weather conditions for years. 

The high initial cost will be offset by increased lifespan and lower maintenance costs. 


Building a rooftop deck is a significant investment. Create a realistic budget by estimating the total cost, including permits and fees. 

Consider financing options that align with your financial capabilities.

Experienced Contractor: 

Hiring a skilled and experienced contractor is essential for a successful project. 

Research, interview, and check references to find the right professional for the job. Do not go for the cheapest contractor as you will only get what you pay for.

Detailed Contract: 

Ensure a smooth construction process with a clear and detailed contract. It should outline the project scope, timeline, and payment terms, providing clarity and accountability.

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Thank you very much for reading the post. I do hope you found it informative and useful.

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