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How To Build A Flat Roof Shed

How To Build A Shed Roof

How to construct a garden room timber flat roof

This article was co-authored by David Bitan. David Bitan is a roofing professional, licensed contractor, and the owner and founder of Bumble Roofing based in Southern California. With over 12 years of construction industry experience, David specializes in restoring, repairing, and maintaining residential, commercial, and industrial roofs. With over 60 years of combined experience, Bumble Roofing provides easy, friendly services to structures including residential, commercial, industrial, multi-family, and government buildings along with hospitals, hotels, and churches.There are 22 references cited in this article, which can be found at the bottom of the page. This article has been viewed 235,361 times.

Whether youre building a brand new shed or re-roofing an existing structure, its important to know the best way to cover it. Start by choosing a roof style that suits your needs and preferences for your shed. From there, you can begin measuring, cutting, and arranging your rafter boards in the desired configuration. After that, its simply a matter of laying down plywood sheathing and installing your roofing material of choice for long-lasting protection against the elements.

What Materials Do You Need To Build A Shed

A List of Materials Needed to Build a 12×12 Wood Shed Wood . Wood will be your biggest expense when constructing your 12-by-12 shed. Paint . After you finish constructing the shed, you will likely want to paint it. Exterior Items. You have several options for the exterior siding of your shed and roof. Gravel . Gravel will provide a draining base for your project.

Add A Protective Roof Covering

In most cases, you will need to add some sort of protective covering to the sheeting. This is particularly the case if you are using the structure to store weather-sensitive materials.

You really have to lock out the cold, rain and moisture. Thus, a protective covering will typically consist of one layer of roofing felt, one layer of tarpaper attached to the roofing felt with an industrial stapler, and then one additional layer of shingles.

In most cases, traditional asphalt shingles will suffice as a form of relatively affordable, yet durable, covering.

Useful links:

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A List Of Materials For Flat Roof Installation

Depending on the type of roof youve chosen either warm flat roof or cold flat roof youll need to gather a number of important materials to build a flat roof.

In addition to basic tools such as a drill, utility knife and measuring tape, youll need the following basic materials, knowledge of local regulations, and a set of detailed instructions:

  • Roofing timber
  • Steel joists
  • Rubber EPDM membrane
  • Water-based adhesive
  • Insulation

How Do You Waterproof A Shed Roof

A Useful Breakdown Of Convenient How To Build A Shed Roof ...

Everybody wants to be able to store things in their shed without worrying about the rain or snow getting inside. Weatherproofing the roof is a very important step when building your shed. These are some important steps to keep in mind:

  • Step 1: Choose a roof design that lets wet weather fall off it easily, such as a gable or lean-to.
  • Step 2: Use felt on the roof before adding shingles. This is just an added layer of protection for the plywood underneath.
  • Step 3: Have a suitable overhang. If you dont, water can be blown back onto the side of the shed and run down the exterior walls.
  • Step 4: Repair roof damages immediately.
  • Step 5: Add gutters.

Waterproofing your shed roof will help ensure a longer life for your shed.

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The Flat Roof Pitch 0 To 10 Degrees

A flatter roof is likely to be a pent style with a bit of roof overhang at the front. Perfect for a shady little veranda in front of a garden summher house.

A flat roof has a pitch of 10 degrees or lower. The main material used for a shed with a flat roof is bitumen mineral felt on top of sheet metal or plywood roofing boards. If choosing a flat roof, keep in mind this will most likely require more frequent maintenance to prevent leaking. Check out the infographic below for more info on vapour membranes.

The building industry has an old saying when it comes to flat roofs: There are those that leak and those that will at some point. Still, dont let this put you off a lovely contemporary pent roof shed.

The maintenance cycle will be less regular if the slant is closer to a 10-degree pitch, but it will still occur more regularly than if using a higher pitch.

An important thing to remember: if an insulated roof is being installed, be sure to allow for an air gap between the roof deck and the insulation for ventilation purposes. This will help prevent moisture build-up and the encouragement of mould growth. In addition, it is always a good idea to follow the manufacturers recommendations.

It is also recommended by some local Authorities to add an additional 5 degrees to the manufacturers minimum pitch for good measure. This helps ensure water tightness.

Cut The Top Plumb Cut

The top plumb cut is made where the rafter will meet the ridge board or the opposing rafter. Use a framing square to lay out the cut based on the roof slope. For a 3/12 slope, align the square so the outside of the short side is against the plank 1/2 to 1 from the end. Pivot the long arm of the square until the 12 mark on the outside is against the plank. Double check that the 3 and 12 marks are at the edge and on the same side of the plank. Draw a line across the plank where the outside of the short arm crosses the plank. You may need to extend the line across the plank. Use a saw and cut at the line.

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Why Do People Build Flat Roofs

When most people think of roofs for their homes, its natural to think of classic pitched roofs. However, there are several reasons why homeowners might need to consider and design a flat roof installation:

  • Zoning or planning ordinances restrict the height of new construction
  • Building a pitched roof would obstruct your neighbors views
  • Building a pitched roof would block sunlight
  • Creating a home extension results in a structure like a shed that fits right up next to an existing building, leaving no space for a pitched roof

You can think of a flat roof for a garage extension or shed that connects with the main house as an example of a flat roof installation project.

Some architectural styles that feature big, boxy designs would be a natural fit for a flat roof.

Suncast Wrs4200 Wooden Vertical 5 Ft X 3 Ft Traditional Shed

How to Build Shed Roof with Overhang Low Sloping Roof Construction

3.7 by user reviews

Conveniently store all of your accessories in one place with the Suncast Wooden 5 ft. x 3 ft. Traditional Shed. This shed has a vertical style, protecting your valuables from any harsh weather conditions and taking up less space than normal sheds. It features swivel hasps and lockable doors. Designed with a flat roof, it has a long roof that helps protect the shed’s interior from excessive sunlight at specific times of the day. Built of wood, it is a perfect addition to any house with its durable and versatile design. This Suncast shed is designed without windows, making it sturdier since it has a solid wall panel. It comes with pre-cut assembly pieces and comes ready to paint. Featuring a traditional design, it will pair well with any backyard, no matter the decor.


    • Constructed of wood, making it a stunning addition to your backyard
    • Made with a plastic roof, making highly resistant to rust, mold, and corrosion
    • Flat roof construct protects the shed’s interior from excessive sunshine at certain times of the day

    • Wooden build can attract termites despite pressure treatment
    • Constructed with a plastic roof, making them more hazardous in cases of fire or extreme heat
    • Flat roof doesn’t drain precipitation very well, therefore, requiring occasional maintenance

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Pulling It All Together

In summary, traditionally a roof pitch was determined by the climate and the available materials to achieve a dry building.

As housing density has progressed and planning rules introduced many sheds have shallower roof pitches due to zoning and planning requirements.

Your shed roof pitch may also be influenced by your project specific requirements to let light into the building through the roof or create storage space in the roof void.

Whichever roof pitch you choose make sure that you select a roof covering that is designed to be waterproof at the angle that you eventually select.

What Is The Cheapest Roof Style

Asphalt Shingles Pros: Asphalt is available in a variety of colors, is easy to source, and is the most affordable roofing application of them all. Cons: Asphalt doesnt last as long as roofing materials, doesnt provide the same kind of insulation as others, and the quality can vary.

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Prepare The Construction Site

Once I decided on the site for my shed, I cleared the area of ground cover. I added 2 on each side of the shed perimeter and hammered in wooden stakes at the corners to give me the area I needed. I removed any sod and the top layer of soil, and then slightly compacted the site to pack down any loose soil.

Building A Flat Roof Right

Shed Roof Designs and Ideas For Your Next Shed

Here’s how the pros construct one so it stays tight and tight

Flat roofs aren’t architecturally logical, as rain and snow will shed much more quickly off a sloped roof. Yet for historic Modern-style buildings like This Old HousesCambridge TV project, flat roofs are at the core of the architecture, meant to reflect the broad horizontal lines of the natural landscape.

Of course, you don’t need to live in a modern house to deal with a flat roof. Traditional homes often have sections of flat roofover shed dormers, above porches and garages, and on balconies. And their horizontal lines abound in the West and in urban areas.

But flat roofs take a pounding from harsh weather, which is why they rarely last as long as a good sloped roof. Fortunately, modern materials for covering flat roofs have improved considerably over the past two decades some carry warranties of up to 20 years, approaching those for sloped roofing.

“If you build and flash one rightand keep it cleana good flat roof won’t leak,” says TOH general contractor Tom Silva, who had seven different flat roofs to contend with on the Cambridge project house. He sealed them all with a glue-down EPDM rubber membrane system, a favorite of his because it’s light, quick to install, and requires no special equipment.

Step 1

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Don’t Make This Mistake When Building Your Shed Roof

I learned the hard way that when you are building your shed, and you are going to shingle it, you can’t have a roof pitch lower than a 3/12. How did I learn this the hard way?

I built a beautiful shed which was a lean to roof style. The roof pitch was actually 2/12. A few weeks later we had a horrendous rain storm and low and behold my shed roof on that shed was leaking like somebody turned on a water faucet in the attic!

What went wrong I thought? After speaking with a nice gentlemen down at the local building department he informed me that if a roof, any roof, has a roof pitch less than 3/12 and it’s going to be shingled it will leak water. No matter whether it rains or you have melting snow. It will leak.

So what was the solution to fixing this water leaking problem with my roof I asked. He told me I had to tear off all the shingles and put down a rubber roofing membrane that would actually be glued to the roof sheeting, then I would be able to re-shingle it. Or I could just go ahead an put on a metal roof. So what I ended up doing was going with the rubber membrane then adding shingles.

Not only did this mistake cause me to have to replace the roof, I also had some interior damage to the inside of the shed.

Lean To Shed Roof Framing

A lean-to roof just means its attached to an existing structure. The high end of the rafter sits on or attaches to a ledger plate attached to the existing wall. The lower end is done the same way a Skillion or shed roof is. Notch a birdsmouth where it sits on the low wall and extend it past the wall for the eaves.

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Globel Gl4000 Metal 6 Ft X 4 Ft Lean

5.0 by user reviews

Complete your outdoor space with the help of the Globel Metal 6 ft. x 4 ft. Shed. Built of metal, this shed offers excellent durability, which makes it a reliable choice for any backyard. It features a door latch and lockable doors. With a flat roof, it has a long roof that protects the shed’s interior from extreme sunshine at certain times of the day. Featuring a metal roof, it is a sturdy choice for your backyard that requires little care. This Globel shed has a lean-to design, using one side of your house’s wall, which provides strong support. Designed without windows, it is more secure than sheds with windows since potential burglars can’t see what’s inside, deterring them from trying to break-in.


    • Constructed of metal, offering unmatched durability and a stylish appearance
    • Flat roof design will efficiently help protect the interior of the shed from extreme sunlight
    • On the more affordable side

    • Metal build is prone to condensation
    • Flat roof requires periodical maintenance and upkeep to keep it in top shape
    • With a windowless design it lets in less natural light

Take A Good Close Look


Here is a close up look at the point at which a simple corrugated iron roof is connected to the fascia panels.

As you can see, the steel has been folded over the edge of the fascia panel to help keep water, snow, and ice from seeping under the edge of the roof. It also extends over the soffits for the exact same reason.

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Arrow Brentwood Bw54 Metal 5 Ft X 4 Ft Barn Shed

3.5 by user reviews

The Arrow Metal 5 ft. x 4 ft. Barn Shed ensures easy and convenient storage for DIY tools and outdoor gear. Made of metal, this shed offers outstanding durability, which makes it a reliable choice for any backyard. Constructed with a metal roof, it is a strong choice for your backyard that requires minimal care. It has a flat roof construct, which efficiently protects the interior of the shed from extreme sunlight at specific times of the day. This shed has a sloped roof, a door latch, and lockable doors. With a windowless design, it is more secure than sheds with windows since potential burglars can’t see what’s inside, discouraging them from attempting to break-in. It has a barn design, which can easily be converted to a playhouse for younger children, an entertainment area, or additional storage area. Built using galvanized steel construction, it provides an extra barrier for added security and strength.


    • Constructed of metal, providing outstanding durability and an aesthetically pleasing look
    • Flat roof design will effectively help protect the interior of the shed from harsh sunlight
    • A sliding door has the versatility of opening the door as wide or as narrow as you like

    • Constructed of metal, making it susceptible to rust, which could eventually corrode
    • Flat roof accumulates precipitation and doesn’t have a good drainage system
    • A sliding door is not very good at sound proofing

Add The Roof Sheeting

Conceptually, you now have a shed with four walls and a series of trusses extending the full length of the structure.

All thats left to do is to add the roof sheeting. This, however, requires a bit of preparation in advance.

You will need to ensure this roof sheeting has the proper protection, so you must fix soffit boards, rafter end trim and filler pieces between the top of the roof plate and the underside of the roof deck.

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What Is The Cheapest Way To Roof A Shed

The most budget-friendly roofing material is MSR. It is similar to conventional asphalt but comes in wide rolls. Aside from being less expensive than shingles, it is also thinner and easier to install. If your roof has a slope, then roll roofing can be installed with nails. A torch-down method is used for flat roofs.

Which Is The Easiest Shed Roof Pitch To Build

Close Up Of How I Did The Outrigger

In my view it has to be the flat roof with a nominal slope. My reasoning for this is that all that is required is a simple beam.

There is no fabrication of roof trusses required. The roof joists can be fixed spanning directly between wall plates. I always recommend at least a minimum pitch of 1 in 40. This translates into a fall of just under 2.5″ on an 8 foot roof.

Fix your roof deck and you are done!

Potential roof framing for a flat roofed shed. The roof comprises a simple beam.

Building roof structures for steeper roof pitches involve different methods. Have a look at the shed roof design and shed roof construction pages to see the construction stages for shed roofs of other pitches and types.

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