How Far Should A Metal Roof Overhang Gutters?


Roof installation is tricky business at the best of times. The use of metal roofing panels presents unique challenges that must be factored in to avoid problems down the line.

Metal roofs should have a 1 inch overhang due to the increased water speeds as rainwater streams toward the gutters over its smooth surface. Gutters should also be larger in order to catch the up to 40% more water per second rapidly spilling into their metal troughs.

Today I focus on the relationship between your roof and your gutters. Our particular focus is on how much overhang metal roofing should have over gutters. I also have a brief how-to guide on metal roof panel installations that could come in handy and help you understand your overhangs. Let’s get started.

How Much Should A Metal Roof Overhang Gutters?

The importance of roof gutters cannot be overstated. Gutters are essential for protecting a building’s foundations because they safely channel water away to prevent soil erosion at the base. Gutters also protect building sidings from direct exposure to dripping water.

Metal roofs should overhand gutters no more than 1 inch due to the increased speed water flows down their smooth surfaces when compared to asphalt, wood, or stone shingles. Larger 6 inch gutters are also advised to accommodate the increased flow of water.

Equally important to the presence of gutters is the positioning of roof edges in relation to them. For gutters to be effective, the roof edge (or overhang) must be positioned in a manner that allows all rooftop rainwater to trickle down into the gutters.

It is vitally important to keep leaves, sticks, and debris from your gutter downspouts to keep them free and clear. I recommend these cheap and effective downspout screens from Amazon to save your foundation from the corrosive effects of water.

Overhangs Depend On Gutter Size

Too much overhang and water will overshoot the gutter and land right beside the building. Too little and some water may fall behind the gutter and drip down the walls. 

The overhang must also leave enough room for the gutters to be cleaned, especially if they are small. Too much overhang may make it difficult to scoop out debris like leaves and twigs. 

In the U.S., most domestic rain gutters are either 5-inches or 6-inches wide. The former is the standard on most homes with traditional roofing materials like clay and asphalt. 

However, the fast-paced flow of water on a metal roof may necessitate a switch to larger 6-inch gutters, which can accommodate up to 40% more water. Therefore, larger gutters can accommodate greater overhangs than smaller ones.

So, how much overhang can a roof have over a gutter?

Roofing Material Matters

Well, that depends on a few factors, with the main one being the roofing material in question.

Roofs consisting of clay tiles and asphalt shingles have enough friction to slow down the flow of water, even during heavy rains. As a result, it is possible to have the roofs overhang further above the gutters. 

Typically, shingles without drip edge flashing should have an overhang of about 1-1 ½ inches over a gutter. With drip edge flashing, you can reduce your overhang to about ½ – ¾ of an inch. As of 2012, shingle roofs must be fitted with drip edge flashing as per International Building Code requirements.

Metal roofing panels, on the other hand, are an entirely different kettle of fish. Because of its (usually) smooth surface, metal will hardly slow down the flow of rainwater. Depending on the gradient of the roof (among other things), rainwater will run down metal panels at greater speeds than it would on clay or asphalt.

As a result, we recommend that you allow your metal roof to overhang the gutters by 1 inch. The extent of the overhang depends on:

  • Your local climate and environment
  • The size of your gutters
  • The type of metal roofing
  • The pitch of the roof
  • The size of the roof

Roof Pitch Plays A Part In Overhangs

The size and pitch of your roof can also affect the momentum of water flow, which directly influences the amount of overhang over gutters. Large steep roofs do not require as much overhang as flatter roofs with smaller areas.

This is further compounded when choosing metal roofs due to the increased waterflow. With 40% more water in a shorter amount of time normally for a metal roof, increasing the pitch also increases the speed the water travels.

Climate And Corresponding Weather Affects Roof Dimensions

Your local climate is another consideration. If you live in an area that receives lots of heavy rains, you might want to opt for a shorter roof overhang. Also, a short overhang is a good way to go if you live in a very windy area. 

Strong gusts of wind are quite capable of ripping a metal roof panel out of position. Too much overhang only increases this risk. This is why drip edges are recommended in areas that experience wind-driven rain, hurricanes, and tornadoes.

Read more of my articles about lawn and home maintenance here…

How To Install A Metal Roof Panel With Existing Gutters?

DIY roof installation may seem daunting at first, but it’s pretty straightforward. Metal roofing is an increasingly popular choice these days because of its longevity, aesthetic variations, and lower long-term maintenance costs.

Step One: Measurements

The first step of a roof installation is measurement. You need to be aware of the specific dimensions (length, width, rise) of your roof sections before ordering your materials. Safety is the number one priority here, especially when climbing the roof.

Determining Slope For Metal Roofs Is Critical

You also need to determine the roof’s slope factor. This is done by:

  1. Multiplying the rise by itself
  2. Multiplying the run by itself
  3. Adding the above answers
  4. Finding the square root of the total
  5. Dividing square root by the run

In a nutshell, the roof’s slope factor = √(rise2 + run2) ÷ run.

The slope factor is then used to determine the area of a roof section. This is done by multiplying the raw roof area (length by width) with the slope factor value. Repeat this for each section of the roof.

Roof Square Footage

At this point, you will be able to find your roof’s total square footage. This is done by adding the area values of all sections. The total square footage equates to the size of roofing material you will need. We recommend that you get 5-10% extra material in case of wastages or measuring errors.

Step 2: Worksite Setup

Once you have received your roofing material, you will need to set up a worksite. Your worksite should include scaffolding, a ladder, trash cans, and a tool platform. 

Speaking of tools, you will need:

  • A staple gun
  • A drill and drill bits
  • Metal shears
  • 1 ¼ inch roofing nails
  • Metal roofing screws 
  • Wood screws

Step 3: Removing Or Keeping The Existing Roof

After setting up the site, you will be faced with a decision: removing the existing roofing or laying the metal panels over it.

We recommend removing the existing roof. Take great care to avoid rushing through this task as it is pretty risky. Protruding nails dropped tiles, and the ever-present risk of falling are just some of the things to worry about here. You can either dump the tiles in the trash cans or store them for future use elsewhere.

Ensure you remove your roof on a dry day. A roofless building is highly susceptible to water damage.

Removing the roof also allows you to change or adjust your gutters so they can be compatible with the new roof panels. You should also repair underlying wood sheathings, air vents, and insulation before laying the new roof.

We recommend you add a new insulation layer and a breathable membrane. This layer will protect the wood sheathings in case any water gets beyond the roof panels. The insulation should be secured with a staple gun or nails.

Step 4: The Roof And Flashing Installation 

Although drip edge flashing is still optional for metal roofing, we recommend that you use it, especially for minimizing overhang over gutters, as well as protecting underlying wood panels.

Metal Roof Flashing Aides Overhangs

The metal strips that will serve as your edge flashing must run right around the edge of the roof and be secured to the sub-roof using 1 ¼ inch nails. The flashing must overlap gutters by about ½ – ¾ of an inch.

After the edge flashing is in place, you can begin installing the metal panels.

Install Metal Panels At The Same Overhang As The Flashing

You should always start at the point with the greatest distance between the roof peak and eave. The first metal panel will set the tone for how the others will sit on the roof. Ensure this panel sits perpendicular to the roof edge (or edge flashing, if applicable). The panel’s overhang must be precisely the same as that of the flashing.

The panel must be secured to the wood sheathing below using washer head screws with rubber seals. Starting from the roof peak and working downwards, drill holes and secure screws at 12-inch intervals. Avoid overtightening as this could damage the rubber seals.

Once the first panel is in place, secure the others in a similar fashion. Each panel must overlap with an adjacent panel by at least an inch to prevent water leakage.  You can also use silicone sealants to secure the panels together even further. 

When the entire roof is covered with panels, you will have to add the roof joint flashing. These thin metal strips are made to cover the gaps between panels in different sections of the roof since overlapping isn’t possible. You may need to bend the strips into a “V” shape for them to fit over ridges.

The flashing must be secured by the same washer head screws used on the panels. Work from the top and use one or two rows of screws for each piece of flashing.

Once the panels are in place, you will have to inspect your work thoroughly. Ensure that each panel is securely in place and overhanging consistently. Also, check for any loose screws and improperly positioned flashing.

The Final Touches On How Far Metal Roofs Should Overhang Gutters…

With the popularity of metal roofs and the relative ease of their installations, many aspects may be unclear for the DIY installer. There are many foreign aspects metal roofs require expertise in that are not applicable to shingled versions.

There are water proofing gaskets and ridgeline insulations as well as different dimensions for gutter overhangs. The overhang for most metal roofs should not exceed 1 inch, but this also depends on pitch and flashings.

Keeping water away from a foundation is one of the most important jobs of roofs and gutter systems. Installing them at the proper size and with the proper overhand is crucial for the longevity of your home.

Here are some more articles I recommend…

References

https://www.hunker.com/13402455/how-much-roof-overhang-for-a-metal-roof

https://www.wikihow.com/Install-Metal-Roofing

https://www.youtube.com/watch?v=SetghGeDP1Q&ab_channel=DaltonRoofing

Mathew Booe

Mathew has worked in landscaping professionally for over 10 years. He is a grandpa and frequently interviews other experienced landscapers and lawn care experts who are also grandpas for these articles.

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