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Things You Should Know About Roof Scuppers

Roof Scuppers

There is a great importance of roof scuppers as it is considered as the drainage system for the flat roofs. It is because the flat roofs do not depend upon the traditional gutter system. So, roof scuppers are defined as the drainage to your roof system as it allows the water runoff from the roof through the parapet wall or metal edge.

This guide provides you with detailed information regarding the important factors and things associated with roof scuppers.

Roof Scuppers: Pros and Cons

Roof Scuppers: pros and cons have been discussed below:


Roof scuppers are cost-effective as they are less expensive than other drainage systems for the roof. The size of roof scuppers is wide and they are easy to install and maintain. You do not have to spend a lot of money on its maintenance. But you should get it inspected regularly so that you could repair it immediately when needed.


The scuppers of small size do clog. So, it can result in causing water to seep under your roof’s edge. When the scuppers are not connected with the downspout, they make the waterfall. So, the falling of water can result in causing erosion around the foundation. The scuppers can spill over if the water pools are near the edge of the roof.

Types of Roof Scuppers

There are two major types of roof scuppers i.e., channel-type scuppers and thru-wall scuppers. These types have been described below:

Channel-Type Scuppers

It is a type of scupper which is also lined with metal; in the case of channel-type scuppers, the metal is integrated with the other edge metal. Some other materials are also used in this type of scupper for instance liquid-applied waterproofing resin. This material is used for lining the hole of the scupper.

Thru-Wall Scuppers

This type of scupper is usually linked with a sheet of metal such as copper or galvanized steel. We know that aluminum is not used for this purpose because it is difficult to form a scupper using aluminum. It is majorly used for fulfilling your design needs.

Roof Scupper vs. Roof Drain

Roof scupper and roof drain both provide drainage to your roof system but the difference is that in the case of roof drain the water running off from your roof goes from the roof drain to the piping which runs into the interior of your house. While in the case of a roof scupper, the water running off from your roof goes from a metal edge into a downspout without running through the interior of your house.

Protection against the water is not provided by the roof scupper. That's why you should not install them when the drainage system cannot be installed outside your house. On the other hand, a roof drain provides you protection regarding water as it prevents water from leaking. So, you can install it if you cannot let the water drain outside your house.

Working of Roof Scuppers

You must be thinking about the importance of roof scuppers and why is a flat roof in the condition to need a roof scupper? It can be explained by describing the working of roof scuppers which will explain their need and importance. Flat roofs need roof scuppers so that water could be drained from the roof.

Rain can result in collecting water on the roof. You should drain this water otherwise it will damage your roof. The flat roofs are designed in a way that water cannot be drained automatically. That’s why roof scuppers are installed.

The working mechanism of roof scuppers is very simple as the water escapes from the roof either from passing through the interior of your house or draining the water outside directly. If the scupper becomes blocked, it does not allow water to pass through it which may also result in leaking your roof.


What Is a Roof Scupper?

A roof scupper can be defined as a drainage system that is mostly preferred from flat roofs. It is a pathway that allows the water to pass from one edge of the roof to the piping or other edge so that water could be drained out. It saves your roof from getting damaged by water. You can save the life of your roof by reducing and making it long-lasting.

How To Make a Roof Scupper?

Sheet metal is used to make a roof scupper as you can install by cutting a wide chunk through your roof. You should keep the scupper wide so that the debris could pass easily without blocking the scupper. You should use metal instead of using aluminum for making the roof scupper. It is because this material helps in draining the water and debris frequently from the roof.

When A Roof Scupper Is Too High?

A roof scupper is too high when there is a great difference between the roof and the floor. In case of overflow scuppers, they must be positioned two or three times higher than the usual. The height of a roof scupper must be at least ten feet depending upon the area of the roof to be drained.

How To Clear or Clean a Roof Scupper?

You can clean a roof scupper by cleaning all the dirt, debris, and weeds using a brush. You can also clean it using your hands by wearing gloves. You can also clean it by running pressure water through the roof scupper so that all the debris could be cleaned out.

How To Calculate Roof Scupper Sizes?

You can calculate the size of a roof scupper by multiplying the square ft. on the table by five. Then, divide it by the local rainfall rate. In most of the cities and areas of the United States, the recommended size of a roof scupper is 4 inches i.e. 102mm. The width of the scupper must be more than the size of the circumference of the roof drain.

How To Insert a Lower Roof Scupper?

You can insert a lower roof scupper by using rubber material i.e., EPDM rubber by cutting its edges. The lower roof scuppers are known as primary scuppers that can be inserted in the parapet wall next to the lowest points of your roof.

How To Seal a Roof Scupper at a Wall?

You can seal a roof scupper at a wall with caulking. You can also do it by installing the rubber membrane over the areas on the wall where there are cracks. The seal is helpful in preventing water leakage. Plus, it does not allow debris to enter the drain pipe.

How To Install a Scupper on A Flat Roof?

You can install a scupper on your flat roof by gathering the necessary tools, hiring an expert, and taking the measurement of your roof and the scupper. You should cut the scupper in the size of 4 inches and the width should be equal to the circumference of your flat roof.

You can get a scupper that lets the water drain through the interior of your house. You can also get a type of scupper installed on your flat roof which lets the water drain outside your house.

How Much Water Can Run Through a Roof Scupper?

It is estimated that about 7.79 gallons per minute can run through a roof scupper. The water flows frequently if there is no dust and debris stuck in it. So, make sure it is cleaned from the inside.

How Much Water Drains Out of a Roof Scupper?

More than seven gallons per minute of water drains out of a roof scupper. All the standing water on the roof drains out because the size of the scupper is large enough to run away all the water through it.

What Is a Scupper Drain Roof?

A scupper drain roof is a roof where a scupper drain has been installed to drain out all the water from the roof. The scupper is helpful to protect your roof from standing water.

How To Pitch a Flat Roof Toward Scupper?

You can pitch a flat roof towards a scupper by installing a shallow pitched roof over your flat roof. You can also add a trussed ranch-style roof to pitch your flat roof.  

How To Run a New Roof Scupper?

You can run a new roof scupper bypassing some water through it. For this purpose, you can take some water in a bucket and throw the water in the new roof scupper to let the water pass through it.

How To Build a Roof Scupper?

You can build a roof scupper by welding the interior edge of the metal sheet and installing flashing. You can use screws for securing the scupper in its place. You should remove the membrane pieces from the place where you are inserting the scupper. Create holes in the metal of about 12 inches. At last, weld the scupper for two inches.

How To Flash Downspout Scupper at Confluence of Three Roof Slopes?

You can flash downspout scupper at the confluence of three roof slopes by using three downspouts on each side with the addition of expansion joints. For this purpose, you must determine the area and pitch of the roof.

Standing Water Flat Roof How to Divert to Scupper on Top of Membrane?

You can divert water to the scupper on top of the membrane by installing drainage pipes. These pipes help in carrying away all the standing water from your flat roof.

How To Frame a Flat Roof to Pitch Toward Scupper?

You can frame a flat roof to pitch toward the scupper by using prefabricated trusses. For this purpose, you need to know about the length and width of the roof.

What Size Scupper Do You Need For a 10 By 50-Foot Flat Roof?

The size of the scupper required for a 10 by 50 ft flat roof is 625 needed per square foot area.

How Many Scuppers Per Sq Foot on Roof?

You need one scupper per sq foot on your 10 by 50 ft flat roof.


You must know about the details regarding roof scuppers if you want to install one. You must know how to install it and what its size should be. This guide provides you detailed information regarding roof scuppers.