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How To Build A Flat Roof Over A Deck

Choose Your Deck Team Wisely

Deck Over A Flat Roof

Architects, landscape architects, engineers, green roof professionals, master builders all have their specialties. You may want to interview several of them before deciding on your rooftop deck team. Green roof professionals often have many these resources in house. If not, they will likely consult with an architect or engineer first anyway. Ask them about their process. Find out how experienced they are. Its well worth it.

Do You Need Planning Permission For Decking On A Flat Roof

Please note that if you want to build a veranda, balcony, decking area or raised platform in the grounds of a flat then planning permission will always be required. In addition if a building to which it relates is a listed building, then both planning permission and listed building consent would be required.

Roof Over Deck Designs

Let us know if you like any of the styles from the images in the section above. As for design, there are three main types of roofing that you can choose for your deck. They include:

  • Gable Gable roofs are easier to build since they dont require complex roof framing. They have gables at each end and sloping sides.
  • Hip Hip roofs are similar to gable roofs since they have sloping sides, however, theyre reconnected without using gables. On a deck roof, the supports should have a finished look since theyll be exposed rather than hidden.
  • Shed This is the most common option for deck roofing because its the only one that works with the architecture for many homes.

Also Check: Does Flood Insurance Cover Roof Leaks

Can I Build A Deck On My Rooftop

Can your roof structure support the additional weight? A building code official may be able to help you here. Or not. At a minimum, they will likely know what the loading requirements are in your area. You may also need a master builder or structural engineer to determine the loading capacity of your roof. They can determine whether your existing roof can support the extra weight of a deck. Never build a rooftop deck without checking this first.

There is plenty more design inspiration and information where this came from. Grab your FREE download of the “Rooftop Deck Design Ideas Project Portfolio” and start designing your dream rooftop deck.

Select The Right Decking For Your Rooftop Deck

Building a Deck on a Flat Roof

Rooftop decks are possibly the most punishing area to build a deck. Theyre low clearance , low ventilation and high exposure. They often see the sun all day long. Choosing the right decking to survive – and thrive – in this environment is an important decision.

No more guesswork. Download this FREE “Ultimate Guide to Selecting The Right Decking” now and get the first steps to finding the right material for your project.

Read Also: Will My House Insurance Cover A Leaking Roof

When Is A Flat Roof Needed

Sometimes town planners will not allow the height required for a pitched roof. This is because it may obscure a neighbours view or light. Sometimes a pitched roof is not appropriate for an extension because it would mean obscuring light to the home owners own windows. Usually however, a flat roof is constructed when an extension butts up to an existing building.

To use a pitched roof in these circumstances would mean adding roof valleys or box gutters and make draining the roof difficult and expensive. Using a lean-to flat roof allows water to run easily away from the building into new gutters which can be connected to existing drainage systems or even new soakaways.

Occasionally a new flat roof will be required to replace an old roof, for example asbestos or corrugated tin roofs which are either not allowed under building regulations or are in a complete state of disrepair.

Care should always be taken when removing old asbestos and advice sought from the local council on the correct way to dispose of the asbestos.

Old asbestos roofs are often replaced with flat roofs

Adding A Roof Over A Deck

Building a roof over a deck turns this area into the best possible outdoor living space. There are many advantages to a roof over your deck, such as:

  • It provides shade and keeps your family dry during wet weather.
  • It adds to the aesthetic appeal of the space.
  • Combined with screened sides, it keeps the bugs away while you relax outside.
  • It boosts curb appeal and property value.
  • It increases the square footage of your home with a three-season living room.

The best time to build a roof over your deck is during the construction of the deck itself. If you have an existing deck, its possible to add a roof to it by installing additional supports. Our experts can take care of all this and more. Discuss the following issues with your professional handyman during the deck roof design process.

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Types Of Flat Roof Construction Warm And Cold Flat Roofs

Flat roof construction can come in the form of a warm roof or cold roof depending on the requirement of the owner and architect as they relate to the building regulations regarding heat loss and insulation.

Put simply a warm flat roof has insulation of some kind packed into every available void and a cold flat roof allows air to circulate between the joists. This air is vented at either end of the roof to allow a continuous air flow.

In terms of rules on ventilation, BS 5250: 2011 is the document to view. It states that there should be at least a 50mm gap between the underside of the roof decking and the insulation below it.

The design of the roof, either warm or cold, must be precise. If a warm roof is not fully packed with insulation, yet a constant air flow is not achieved, condensation will form in any unvented void. Condensation forms as warm air hits cooler surfaces and can rot the roof from the inside out.

You will need to look at Approved Document C and also Approved Document F of the building regulations as these documents will help you calculate the amount of ventilation that will be required for your particular project.

This type of condensation is called interstitial condensation. This warm vs cold roof situation also occurs in pitched roofs and it is vital, in simplistic terms that either no air is allowed into voids or a constant air flow is achieved.

What About Composite Decking Material

Installing Flat Roof Deck

Synthetic decking options range from wood composites, to plastic capped wood composites, to cellular PVC. Most are available in a variety of colors. Some may perform well in this harsh area. Most do not. Most of the synthetics heat up and expand and contract making them uncomfortable to walk on. If you are considering this option, please do your homework first.


Also Check: How Much To Replace Roof On Garage

Rubber Membrane Vs Pvc Membranes Flat Roofs

This rubber material resembles an inner tube and can be mechanically anchored with fasteners, ballasted with stone, or glued. It is relatively lightweight and durable, however, the standard black material absorbs heat. There are light-colored options available but they are about 30% higher cost. Comparatively, it is a higher cost option, but it is something a homeowner can install. It does not, however, make a good surface for a flat roof deck and would require an additional assembly to make the flat roof acceptable for that purpose.

PVC Sheet membranes have similar performance expectations, although PVC membranes have 2 distinct advantages.

1 when installed by a professional applicator, PVC membranes are integrated into the building envelope and come with a sound warranty.

2 PVC sheet membranes once again are the only product of these comparisons that provides an attractive walking surface in addition to its roofing membrane performance in a single product application.

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,

Also Check: How To Fix Hail Damage On Roof

Diy Doctors Flat Roofing Advice And Recommendation

In the case of a felt or fibreglass covered roof, we very strongly advise the installation of this by a professional. You will get a guarantee, usually 10 years and that is worth its weight in gold.

If you are felting a flat roof and you do get a leak having done the job yourself, 99% of the time a patch will not work because the water will have seeped under the felt already, causing soft spots to your sheet covering and ultimately rot.

In this case and depending on the severity of the damp the damaged area will need repairing and in severe cases the entire roof may need replacing. Even the repair to a small area can be costly!

Do I Need A Permit To Add A Roof To An Existing Deck

Building a rooftop deck

You need a permit to put a roof over your deck. For one, it is a safety concern. Failure to properly fasten the roof to the house could lead to collapse and injury. Secondly, if you dont attach the roof to the house properly, you could invite significant water damage into your house, resulting in major damage.

Any project involving framing or adjusting existing house framing will require a permit, regardless of where it is on your property. However, unlike a shed, even the smallest addition to your existing house roof will require a permit.

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How To Build A Roof Over An Existing Deck

You may be thinking, Why would I want to put a roof over my deck?

There are many reasons. A roof can help keep you and your guests dry in the event of rain or snow. It could also provide additional shade for those hot summer days and add privacy with its natural screening effect.

If youre thinking of how to build a roof over an existing deck, then you came to the right place. Well discuss how to build a deck with a roof and other related queries.

Dont Install Before You Confirm Integrity Of Existing Roof

Considerations should also include how you plan on finishing off your flat roof, such as water run-off, deck access for maintenance, drainage, etc.

You need to proceed with caution as flat roofs leak regardless of whether they are decked or not, as a result of design errors, insufficient materials, and poor installation. Many roof decks, when installed, further damage roofs, resulting in even more severe leaks and drainage problems.

The first consideration is that the posts on the deck can puncture through and damage your old flat roof if its not supported with additional blocks or beams.

You also need a platform that can support the weight of your deck and any furniture or equipment that might be on it and make sure this platform has enough room for power cables, pipes and other infrastructure such as vents.

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A Balcony With Wooden Floor Or Other

This option is generally quite popular given that it is an affordable one, not only due to the choice of materials, but also because costs related to construction are also quite low. Other than the structural changes that may be required, generally, all you will need to do is add a floor with proper drains in order to assist in water evacuation. Moreover, you will have the choice between different styles for your flooring: sequoia, cedar, yellow pine, etc. You can also opt for vinyl or composite.

Building On An Existing Deck

Installing a Lean-to Roof on an existing Deck

Where local building codes allow this practice, you can bolt a patio overheads posts directly to existing deck beams, joists, or other heavy structural members. Or, you can lag-screw through post bases and decking into the top of a deck joist or beam.

When bolting to the decks structure, be sure to use heavy-duty galvanized lag screws that are long enough to penetrate the decks framing by at least 2 inches.

In some situations, you may be able to use the homes structure to support an overhead above a deck. For a good example of this, see the article This Patio Roof Sheds Water, Allows Natural Light.

Read Also: What Is Recoverable Depreciation On A Roof

S Of Roofs Over Decks

Another great thing about installing a roof over your deck is that you can personalize it to match your style and tastes. The pictures were showing below are just a few of the ways you can build your decks roof. Some homeowners like to have an idea in mind before scheduling an appointment with a construction company while others like to listen to the recommendations of the experts before they begin any decision-making. Take a look at the pictures below to see which ones you like. Then, give us a call to schedule a consultation.

These homeowners are in the process of building a flat roof over their free-standing deck. We cant wait to see how it turns out!

This homeowner chose a short roof with lights underneath. The lights will not only add functionality for nighttime, but theyre also aesthetically pleasing.

This homeowner chose the best of both worlds by adding a roof to their deck that still allows light in.

Were loving the look of this gable roof over the patio in their backyard. Its perfect for hanging out night and day, rain or shine.

This flat roof acts as both a covering for a section of the first-floor deck as well as a balcony for the second floor of the home. Now, thats what we call efficient.

Average Cost To Build A Roof Over A Deck

Unfortunately, we wouldnt be able to tell you how much it would exactly cost to add a roof to your deck without scheduling a consultation and coming to your home. But we can give you an average range of prices that it would most likely fall within. They include:

  • Adding any deck covering or enclosure will typically cost between $1,000 $10,000.
  • Adding a covered roof to your deck will typically cost between $3,000 $10,000.

The cost will vary depending on the professionals hired, materials used, square footage, and weather conditions.

Not a real zip code.

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Designing Your Roof Deck

Hire a reputable builder to handle the design of your roof deck. Many contractors who offer deck building may only provide a few configurations that you can adjust as necessary while others may create something entirely new and unique for your home. Before agreeing to any work, make sure the contractor youve chosen has the necessary licenses and certifications, and ask to see samples of their past projects.

When you work with Mr. Roof for your roof deck project, you can rest assured knowing our team members have the training and experience to ensure your deck doesnt harm the roof below or the rest of your home. We stand by the quality of our work and our building materials with a lifetime warranty.

Design choices are virtually limitless when it comes to building your roof deck. Choosing sustainably sourced wood and decking is a great option for the environment, and most eco-friendly building materials hold up incredibly well against wear and moisture. Check to ensure the design youve selected and the materials your builder recommends work for your area. Some materials are more susceptible to water damage and warping than others in some climates, so heed your contractors advice.

The 4th Flat Roof Roof Decks

Flat Roof Deck Construction

Flat roofs do not always need to be utilitarian in nature. They are ideal locations to extend livable space by creating outdoor leisure areas. With the caveat that safe access is available and the roof is structurally sound to bear the weight of traffic, flat roof decks are a value-added feature to incorporate into building or remodeling plans.

Read Also: How To Measure A Gable Roof For Shingles

Can A Roof Hold A 300 Lb Person

California building code sets minimum standards for roof load-bearing capacity. At minimum, any roof which may be used by maintenance workers must hold 300 pounds concentrated. Concentrated means that this weight can be held by any one spot on the roof. While that is the bare minimum, your roof may need to hold more.

How To Build A Shed Roof Over My Existing Deck

Unless youre experienced in residential roofing construction, you probably dont want to build the roof yourself. However, you might want to know the process of how its done. Take a look at our step-by-step guide for building a shed roof over your existing deck:

  • Step 1: Before you begin, make sure youre matching the house roof pitch angle and overhang for your roof.
  • Step 2: Install post base connectors. These are used to attach the support posts to the frame of the deck. For a solid connection, youll have to make sure the frame has the appropriate blocking.
  • Step 3: Install the support posts to the post base connectors.
  • Step 4: Keep the support posts in place by installing temporary bracing. The tops of the support posts should be notched to hold the header beam.
  • Step 5: Install the header beams to the support posts. We recommend using thru bolts for a strong connection.
  • Step 6: Install the ledger board, which will support the rafters. You can install it by flashing and bolting in place to the house wall.
  • Step 7: Mark and cut your rafter angle to the roof pitch and then lay out your rafters. Nail the rafters in place to the ledger board.
  • Step 8: Attach the rafters to the header using framing nails.
  • Step 9: Create the subroof by installing the roof sheathing over the rafters.
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