WHY FLAT ROOF DRAINAGE IS IMPORTANT

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Common Flat Roof Drainage Systems

The one challenge with flat roofing is ensuring proper drainage. Unlike other roofing types that are slanted or sloped to allow water to drain automatically, flat roofs need a built-in drainage system to help remove moisture and debris. Poor drainage can lead to serious issues with flat roofing, from leaks to structural damage. There are several drainage solutions available for flat roofing and it is important to consider the pros and cons of each system before making a decision.

Flat roofing does not drain naturally like sloped roofs that can rely on the force of gravity to remove water. If these roofing types are not fitted with a proper drainage solution, they will experience poor drainage which leads to the following issues:

Pooling of water on the roof that can eventually lead to leaks or structural damage
Accumulation of debris such as twigs and leaves
Damage to the caulking and tar from debris buildup and pooled water
Extra stress from ice in the winter
Leaks near features of the roof such as the chimney or vent pipes

Leaving your flat roof without a drainage system will greatly increase the risk of these issues. Fitting the roof with one of the following systems to ensure proper drainage will help keep it protected.

Internal Drains

Internal drains are installed at low points on a flat roof. They collect water and send it through pipes inside the building to the ground. Internal drains usually have strainers to catch debris.

Pros and cons

Pros: They prevent water from overflowing the roof edges and protect walls from damage. Internal drains can also handle heavy rainfall.

Cons: They require regular maintenance to remove debris. If not maintained, they can cause water backups and leaks.

Scuppers

Scuppers are openings in the walls or parapets of a flat roof. They let water flow off the roof and onto the ground or into a gutter system. Scuppers often have a slight slope to help water drain faster.

Pros and cons

Pros: Scuppers are simple and cost-effective. They can handle large amounts of water and are low-maintenance compared to internal drains.

Cons: Scuppers might not work well in heavy rain if they’re not big enough. They can also cause water to splash onto walls or landscaping below.

Gutters

Gutters are long, narrow channels attached to the roof edges. They catch water flowing off the roof and direct it to downspouts. Downspouts then carry the water to the ground or a drainage system.

Pros and cons

Pros: Gutters are a familiar drainage solution and can prevent water from splashing onto walls. They also help control the flow of water around your building.

Cons: Gutters need regular cleaning to remove debris. If not maintained, they can become clogged, causing water to overflow and potentially damage your roof or walls.

Crickets

Another important component in the way flat roofs drain is the use of crickets. A cricket is a triangular structure used to divert water away from certain areas on a roof where it may become trapped, similar to chimney crickets in residential roofing systems. Crickets are almost always made out of insulation. The insulation is built up under the roof membrane in such a way that it creates a triangular structure, adding a little more slope to the roof to prevent water ponding. Roof crickets are usually placed near walls, around HVAC units and skylights, and around drains. When properly designed, crickets are extremely effective at diverting water where it needs to go to drain off of the roof and protecting against the issues that come along with standing water.

Central Roof Drains

Central roof drains, also called “inner drains” are often found on commercial roofs. These drains are placed at the center of a roof, and roof crickets, or the natural roof slope are used to direct water to these areas. These drains are a particularly good option for very large roofing systems. They attach to pipes that run down through the building’s roof to carry water down and out of the building safely. These drains are also a great option for colder climates, because they are not vulnerable to freezing and cracking during the winter since they are protected by the building’s insulation.

Factors Affecting Flat Roof Drainage

Roof slope and design

Even flat roofs have a slight slope to help water drain. A well-designed slope ensures water flows to the drainage system. If the slope isn’t right, water might pool on the roof.

Climate and rainfall

The amount of rain your area gets affects your flat roof drainage. Heavy rainfall can overwhelm your drainage system if it’s not designed to handle it. Consider your local climate when planning your roof’s drainage.

Debris accumulation

Leaves, twigs, and other debris can clog your drainage system. This can cause water to back up and damage your roof. Regularly clearing debris keeps your drainage system working well.

Proper maintenance and inspection

Regular maintenance and inspection help keep your drainage system in good shape. This includes cleaning drains, checking for damage, and fixing any issues. Proper maintenance prevents water damage and extends the life of your roof.

How to Figure Out the Drainage Requirements for Flat Roofs

Wondering how to figure out the drainage requirements for flat roofs? And how many roof drains you might need?

First, we need the following information to design the drainage system properly:

Maximum rainfall rate: You need to know the heaviest rainfall expected in the area where your building is. You can find this information in weather maps or some roof drainage calculators.
Roof area: How large is your roof? You need to know the total area you are working with.
Roof pitch or slope: Even though we’re talking about flat roofs, there’s still a little slope, like 1/4″ per 1 foot. This matters when calculating drainage.
Drainage components: You need to know the size of the roof drains, gutters, drain piping, or downspout leaders. For example, they might be 6 5/8″ inside diameter.

Next, we must consider the required roof drainage rate in liters per second. This depends on the type of roof covering, any roof projections or penetrations, and the roof’s structural strength to handle the weight of water or wet snow. Finally, we need to think about roof drain flow resistance factors, like drain slope, constrictions, elbows, and bends. Plus, make sure we are following any local and model code requirements or standards for roof drainage in our area.

So, unfortunately, there’s no easy rule of thumb for the number of roof drains needed on flat roofs. But if you gather all the info above, you can design a solid drainage system.

Tips for Flat Roof Drainage

Proper installation techniques

Hire professionals to install your drainage system. They know the right techniques to ensure your system works well. Proper installation helps prevent future problems and saves money.

Choosing the right drainage system

Consider your roof’s size, shape, and local climate when choosing a drainage system. Talk to an expert for advice on the best system for your needs. The right system keeps your roof dry and damage-free.

Seasonal maintenance recommendations

Different seasons bring different challenges for your roof. Inspect and clean your drainage system before and after winter. Remove leaves and debris in the fall. Regular seasonal maintenance keeps your roof in good shape all year.

Conclusion

Remember to maintain and inspect your system regularly to prevent problems. Effective drainage keeps your flat roof dry and damage-free. It also extends the life of your roof and saves you money on repairs. Make proper drainage a priority in your flat roof maintenance routine. With the right system and regular care, you’ll enjoy a long-lasting, efficient flat roof. Stay proactive and protect your investment!

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CALL OR EMAIL US TODAY FOR YOUR FREE ESTIMATE – 202-276-5004 FAMILY.ROOFING@YAHOO.COM

WHY FLAT ROOF DRAINAGE IS IMPORTANT

Common Flat Roof Drainage Systems

Flat roofing does not drain naturally like sloped roofs that can rely on the force of gravity to remove water. If these roofing types are not fitted with a proper drainage solution, they will experience poor drainage which leads to the following issues:

Pooling of water on the roof that can eventually lead to leaks or structural damage

Accumulation of debris such as twigs and leaves

Damage to the caulking and tar from debris buildup and pooled water

Extra stress from ice in the winter

Leaks near features of the roof such as the chimney or vent pipes

Leaving your flat roof without a drainage system will greatly increase the risk of these issues. Fitting the roof with one of the following systems to ensure proper drainage will help keep it protected.

Internal Drains

Internal drains are installed at low points on a flat roof. They collect water and send it through pipes inside the building to the ground. Internal drains usually have strainers to catch debris.

Pros and cons

Pros: They prevent water from overflowing the roof edges and protect walls from damage. Internal drains can also handle heavy rainfall.

Cons: They require regular maintenance to remove debris. If not maintained, they can cause water backups and leaks.

Scuppers

Scuppers are openings in the walls or parapets of a flat roof. They let water flow off the roof and onto the ground or into a gutter system. Scuppers often have a slight slope to help water drain faster.

Pros and cons

Pros: Scuppers are simple and cost-effective. They can handle large amounts of water and are low-maintenance compared to internal drains.

Cons: Scuppers might not work well in heavy rain if they’re not big enough. They can also cause water to splash onto walls or landscaping below.

Gutters

Gutters are long, narrow channels attached to the roof edges. They catch water flowing off the roof and direct it to downspouts. Downspouts then carry the water to the ground or a drainage system.

Pros and cons

Pros: Gutters are a familiar drainage solution and can prevent water from splashing onto walls. They also help control the flow of water around your building.

Cons: Gutters need regular cleaning to remove debris. If not maintained, they can become clogged, causing water to overflow and potentially damage your roof or walls.

Crickets

Central Roof Drains

Factors Affecting Flat Roof Drainage

Roof slope and design

Even flat roofs have a slight slope to help water drain. A well-designed slope ensures water flows to the drainage system. If the slope isn’t right, water might pool on the roof.

Climate and rainfall

The amount of rain your area gets affects your flat roof drainage. Heavy rainfall can overwhelm your drainage system if it’s not designed to handle it. Consider your local climate when planning your roof’s drainage.

Debris accumulation

Leaves, twigs, and other debris can clog your drainage system. This can cause water to back up and damage your roof. Regularly clearing debris keeps your drainage system working well.

Proper maintenance and inspection

Regular maintenance and inspection help keep your drainage system in good shape. This includes cleaning drains, checking for damage, and fixing any issues. Proper maintenance prevents water damage and extends the life of your roof.

How to Figure Out the Drainage Requirements for Flat Roofs

Wondering how to figure out the drainage requirements for flat roofs? And how many roof drains you might need?

First, we need the following information to design the drainage system properly:

Maximum rainfall rate: You need to know the heaviest rainfall expected in the area where your building is. You can find this information in weather maps or some roof drainage calculators.

Roof area: How large is your roof? You need to know the total area you are working with.

Roof pitch or slope: Even though we’re talking about flat roofs, there’s still a little slope, like 1/4″ per 1 foot. This matters when calculating drainage.

Drainage components: You need to know the size of the roof drains, gutters, drain piping, or downspout leaders. For example, they might be 6 5/8″ inside diameter.

So, unfortunately, there’s no easy rule of thumb for the number of roof drains needed on flat roofs. But if you gather all the info above, you can design a solid drainage system.

Tips for Flat Roof Drainage

Proper installation techniques

Hire professionals to install your drainage system. They know the right techniques to ensure your system works well. Proper installation helps prevent future problems and saves money.

Choosing the right drainage system

Consider your roof’s size, shape, and local climate when choosing a drainage system. Talk to an expert for advice on the best system for your needs. The right system keeps your roof dry and damage-free.

Seasonal maintenance recommendations

Different seasons bring different challenges for your roof. Inspect and clean your drainage system before and after winter. Remove leaves and debris in the fall. Regular seasonal maintenance keeps your roof in good shape all year.

Conclusion