Published on December 12, 2022 by Jason Reisman

How to Slope a Flat Roof for Drainage: Expert Guide

When you need to slope a flat roof, contact Eustis Roofing’s expert roofers at (352) 343-4240.

Traditionally sloped roofs help redirect water away using gravity for faster runoff. Because steep single- or double-sloped roofs don’t allow precipitation to pool, there’s less chance of it weighing down certain spots, rotting your roof structure, or creating fungal growth. But how does a flat roof drain?

Our family-owned and -operated business has over 60 years of experience with flat roof repair and installation processes. To understand how to slope a flat roof for drainage, trust Eustis Roofing in Leesburg, Eustis, and other surrounding Central Florida areas. 

How Professionals Slope a Flat Roof

The term “flat roof” is deceptive: a flat roof isn’t perfectly horizontal with a zero-degree slope. Instead, it tilts slightly to one side, allowing runoff without giving the appearance of an angle. The pitch, or slope, averages one to ten inches of rise per each foot of run to send water to their drainage systems. 

However, depending on how you plan to slope your roof, you’ll have a different and complex drainage system.  

Gutter Drainage

Gutters are necessary on sloped and flat rooftops since they’re a simple and affordable way to drain water. The galvanized steel, aluminum, or vinyl gutters run along the roof’s edge, collecting water and small particles before leading them to the downspout. Unfortunately, gutters are also the most visible and easily clogged systems, requiring more maintenance and repairs. 

Siphonic Drainage

You don’t have to think too hard about how to slope a flat roof for drainage with siphonic drainage. Even a minimum slope with a rise under one inch per foot drains efficiently with this system. especially when combined with efficient roofing solutions like CertainTeed’s Flintlastic SA Cap. With numerous outlets around the roof’s circumference connecting to one major pipe, siphonic drainage works faster and doesn’t require special pitch pipes like other systems. 

Inner Drainage

Inner drainage is best when improving curb appeal since these systems on flat roofs are invisible from ground level. You won’t see piping or gutterwork. Because the pipes go underneath the roof for proper drainage, you can build a rooftop bar, garden, lounge, or pool area without worrying about visible drain pipes on the surface.

Choose how your contractor slopes your roof if installing a new roof before adding the system. When considering how to slope a flat roof for drainage you can either direct the slope downward on one side or concave the roof’s center. Then, add the inner drain to the lowest point to catch runoff. 

Don’t Send Your Estate Into the Gutters: Protect It with the Pros!

Without a proper drainage system on your roof, your roof’s structure weakens. Pooling water can seep into your roof’s underlayment and the attic, causing water damage and jeopardizing your home’s structural integrity. If you’re wondering how to slope a flat roof for drainage, count on our roofers at Eustis Roofing.

At Eustis Roofing in Leesburg, FL, we have nine full-time, five-star teams that work around the clock to assist with anything from sealing a flat roof to replacing a slanted roof. Call (352) 343-4240 to get a free quote today!

Jason Reisman

About The Author: Jason Reisman

Jason Reisman, ERC’s General Manager is a problem solver! Jason is hands-on with finding solutions to difficult problems as well as constantly researching, exploring new concepts, discovering new inventive ways and is passionate about being the most experienced, most knowledgeable and most dependable in the roofing trade. He’s hands-on with training and instruction ensuring every job have the up to date and state of the art equipment to perform with precision to be in and out without delays. Jason loves competing with his Dad on the golf course!