Flat roofs are a popular option for both residential and commercial structures since they maximize usable space and offer a clean, modern style. Nevertheless, flat roofs do have one problem, and that is the inability of them to naturally guide water off the roof the way sloped roofs do.
If water doesn’t have a way to leave the roof, it’s known as standing water, which can cause damage, leaks, and expensive repairs if there isn’t an adequate drainage system in place. That’s why, to help you out, this blog post we will discuss the different flat roof drainage systems, their importance, and how to select the best one for your home.
Why Flat Roofs Need Drainage
There are numerous reasons why a flat roofing system needs adequate drainage, including the following:
1. Prevent Pooling Water
Flat roofs need drainage to stop water from collecting and causing leaks due to ponding water.
2. Protect the Structure
Standing water adds weight to the roofing system, which can strain the structure and lead to leaks.
3. Maintain Energy Efficiency
If leaks occur, it can affect the insulation below, increasing energy costs and lowering efficiency.
4. Prevent Deterioration
Continuous water exposure wears down roofing materials, shortening the roof’s lifespan.
5. Extend The Roof’s Lifespan
Proper drainage prevents damage and deterioration, making the roof last longer.
Options For Creating The Best Flat Roof Drainage System
To ensure your flat roofing system keeps your interior safe and dry, let’s explore the best options for flat roof drainage that are available to homeowners:
#1. Interior Drains (Central Roof Drains)
Strategically placed at the lowest points of flat roofs, interior drains effectively collect and channel rainwater away from the building’s interior. Connected to concealed pipes, these drains direct water to the building’s drainage system, preventing pooling on the roof.
Ideal for commercial buildings where appearances are key, they keep the roofline clean without visible gutters or downspouts. Their enclosed pipes also reduce the risk of clogs, ensuring efficient water management during heavy rain, and minimizing leaks and water damage.
- Aesthetic Appeal: Hidden pipes keep the roofline’s appearance seamless
- Reduced Clogging Risk: Enclosed pipes limit debris buildup
- Efficient Water Management: Great for large roofs, handling heavy rain efficiently
#2. External/Scupper Drains
Located at the roof’s edges, external drains, or scuppers, facilitate the flow of rainwater off the roof into gutters or downspouts. Typically integrated into parapet walls or the roof’s perimeter, they offer a cost-effective and straightforward installation.
With fewer exposed parts, these drains require minimal maintenance. They efficiently direct water away from the building, protecting walls and foundations from potential damage.
- Cost-Effective: Cheaper to install than internal drains
- Easy Maintenance: Fewer parts to maintain
- Direct Water Flow: Channels water away from the building
#3. Gutters and Downspouts
A traditional choice, gutters, and downspouts collect rainwater running off the roof’s edges and direct it away from the structure. Installed along the roof’s perimeter, they help prevent damage to walls, soil erosion, and foundation issues. Widely available and customizable, this system is both affordable and effective at managing rainwater runoff.
- Affordable and Available: Easy to install and find materials for
- Effective Water Diversion: Protects walls and foundations
- Customizable: Can be tailored to different styles
#4. Siphonic Drainage Systems
Using negative pressure that creates a vacuum effect, siphonic drainage systems rapidly remove rainwater from flat roofs. Requiring smaller pipes, this drainage system is also easier to install, reducing the total cost you have to spend.
- High Capacity: Can handle large amounts of water
- Smaller Pipes: Requires smaller pipe sizes.
- Prevents Ponding: Quickly removes water, reducing risks
#5. Roof Overflow Drains
Overflow drains serve as a secondary safety measure by providing an additional outlet for excess rainwater during storms, or if primary drains fail. Installed alongside the primary drainage system, they ensure that extra water exits the roofing system, preventing flooding. These drains are easy to integrate into existing setups, enhancing safety and protecting against structural damage.
- Backup Protection: Prevents flooding
- Simple Design: Easy to install alongside main drains
- Enhanced Safety: Helps maintain roof integrity
#6. Sloping The Roof Deck
Flat roofs often have a slight slope to direct water towards drains or scuppers, promoting natural runoff and preventing pooling. Proper sloping, customized for specific building needs and weather conditions, reduces wear on roofing materials and maintains roof functionality and structural integrity.
- Natural Water Flow: Enhances drainage efficiency
- Customizable: The slope can be adjusted for different needs
- Prevents Pooling: Reduces the risk of water accumulation
#7. Using Tapered Insulation
Tapered insulation provides a sloped surface on flat roofs without structural changes, directing rainwater toward drains while enhancing thermal efficiency. Its customizable design addresses specific drainage needs and climate conditions, reducing standing water risks and improving energy efficiency.
- Dual Function: Improves energy efficiency and drainage
- Customizable Slopes: Adjusted to building needs
- Prevents Ponding: Keeps water from collecting on the roof
#8. Roof Crickets
Roof crickets are structures that divert rainwater around obstacles like chimneys or vents, ensuring proper drainage flow. Customizable in size and shape, crickets enhance water management by redirecting water to drainage points and preventing pooling around obstructions, thus protecting the roof’s integrity.
- Improves Water Flow: Prevents pooling near obstacles
- Protects Roof Integrity: Enhances drainage around critical areas
- Custom Design: Tailored to the roof’s layout
Factors to Consider When Choosing a Drainage System
Every flat roofing system has its own different needs when it comes to drainage, so to get the best for your system consider the following points:
1. Roof Size and Slope
Larger or flatter roofs need stronger drainage systems, or more than one type of drainage system, like internal drains or a mix of drains and scuppers. Smaller, sloped roofs work well with scuppers or simple gutters.
2. Climate and Rainfall
Areas with heavy rain or snow need systems that handle a lot of water, such as internal drains or a combination of drains and scuppers.
3. Building Structure
Buildings with parapet walls are best with external drains or scuppers. If the roof does not have parapet walls, internal drains are often needed.
4. Maintenance Needs
Choose a drainage system based on how much maintenance you can do. Some require you to frequently remove debris while others are self-cleaning, such as siphonic drains.
Common Problems With Flat Roof Drainage
Even with a good drainage system, flat roofs can face issues:
- Clogged Drains: Debris blocks drains so make sure you clean them regularly
- Ponding Water: Standing water suggests drainage issues that need to be fixed
- Leaks: Water seeping through the flat roofing material can cause leaks, so inspect and make repairs as often as possible.
How To Slope A Flat Roof For Drainage
Flat roofs should have a slight slope of about 1-2% (1/8 to 1/4 inch per foot) to direct water toward drainage points. Tapered insulation can be a successful way to form an adequate slope for your roofing system, however, you will need professional help for installation.
Upgrade Your Flat Roof Drainage System Today With OConnor Contracting
Investing in a good drainage system and keeping up with regular maintenance will protect your flat roof from water damage, extend its lifespan, and keep it a valuable part of your property for years to come.
Need flat roofing solutions? Our team at OConnor Contracting has you covered! We offer expert installation and maintenance of flat roof drainage systems to protect your property. Contact us at (716) 600-7663 for a consultation!
