A flat roof is rarely perfectly flat: it needs carefully planned drainage to keep water moving toward drains, gutters, or roof edges. A flat roof cricket slope is a small raised, sloped area that directs water around an obstruction—such as a chimney, curb, or large rooftop unit—instead of letting it collect behind it. Correct design can reduce ponding and help protect the roof assembly, but slope, materials, and drainage details must suit the roof system and local code.
What Is a Flat Roof Cricket?
A roof cricket, sometimes called a saddle, is a peaked or tapered structure built on the uphill side of an obstruction. Its two sloping faces split and redirect water around the obstruction toward a drain or roof edge. Crickets are commonly used behind chimneys, skylight curbs, elevator penthouses, HVAC equipment, and other objects that interrupt the roof’s drainage path.
The word “flat” describes the roof’s general appearance, not a surface that should hold water. Low-slope roofs need drainage. A cricket adds a local change in elevation to help water get around an obstacle and reconnect with the roof’s drainage route.
A cricket is not the same as the roof’s overall slope. The main roof slope moves water across the roof; the cricket’s shape handles a specific obstruction. It also differs from a drain sump, which is a depressed area intended to direct water into a roof drain.
Why Cricket Slope Matters
Water flowing toward an obstruction can slow down or become trapped along its uphill side. Leaves, dirt, and roofing debris can make the blockage worse. A cricket creates a raised watershed that divides the flow and guides it around the obstruction.
Proper drainage helps limit standing water, which can increase the load on a roof and contribute to leaks when seams, flashing, or other details are vulnerable. Persistent moisture can also encourage algae or material deterioration, depending on the roof system and conditions. A cricket does not guarantee a leak-free roof, but it can address a predictable source of water buildup.
Key distinction: a cricket redirects water; it does not replace roof drains, scuppers, gutters, or a correctly sloped roof. The complete drainage plan must provide a clear path from the cricket to an outlet.
How Much Slope Should a Roof Cricket Have?
There is no single cricket slope that applies to every flat roof. The required slope depends on the roof membrane, insulation system, cricket size, drainage layout, structural conditions, and applicable building code. Project drawings and the roofing manufacturer’s requirements should govern the design.
As a practical design reference, low-slope roofing assemblies commonly use positive drainage slopes, and tapered insulation plans often use slopes such as 1/4 inch per foot. That figure is not an automatic rule for every cricket or every jurisdiction. Some projects use different slopes because of system requirements, existing roof elevations, or code provisions. A qualified designer should confirm the appropriate slope before construction.
For a simple plane, slope can be expressed as a rise over a horizontal run. A 1/4-inch-per-foot slope rises 1 inch over 4 feet. A 1/2-inch-per-foot slope rises 1 inch over 2 feet. The slope needs to be continuous and lead to a functioning drainage point; a number on a drawing is not useful if the installed surface has dips or reverse slopes.
| Example slope | Rise over 4 feet | Practical note |
|---|---|---|
| 1/8 inch per foot | 1/2 inch | Confirm that the roof system and project requirements permit it. |
| 1/4 inch per foot | 1 inch | A common reference used in low-slope roof design. |
| 1/2 inch per foot | 2 inches | Creates faster elevation change but requires adequate space and compatible transitions. |
These examples describe geometry, not a code determination or a guarantee of performance. In the United States, adopted building codes and amendments vary by location. The project team should check current local requirements and the roof manufacturer’s published instructions.
Cricket Size and Shape
A cricket’s dimensions depend on the obstruction’s width, the available roof area, and where water needs to go. A wider obstruction generally needs a broader cricket to divide water effectively. A narrow or poorly positioned cricket can leave a pocket behind the obstruction or send water toward another vulnerable area.
In plan view, a typical cricket resembles a triangle or a low ridge that meets the obstruction near its center. Water flows away from the ridge on both sides. The ridge should be positioned and shaped to send runoff toward suitable drainage paths, not simply around the obstruction without considering where it will land.
Designers also need to account for the cricket’s height and tie-in to the surrounding roof. A cricket that is too low may not divert water reliably. One that is too high can create abrupt transitions, complicate flashing, or interfere with equipment access. The finished assembly should avoid sharp changes that could strain the membrane.
Where Crickets Are Commonly Needed
- Behind chimneys: A masonry chimney can block runoff and create a collection point along its uphill side.
- Behind roof curbs: Skylights, hatches, and equipment curbs can interrupt the drainage route.
- Around large rooftop units: Mechanical equipment may require crickets or saddles to route water around its base.
- Near roof drains: Drainage layouts may use tapered areas to guide water around obstructions and toward the drain.
- At roof transitions: Changes in elevation or roof geometry can create localized areas where water needs to be redirected.
Not every small penetration needs a cricket. Small pipes and vents are often handled with appropriate flashing and the surrounding roof slope. The need for a cricket depends on obstruction size, water flow, roof geometry, and design requirements.
Materials Used to Build a Roof Cricket
Crickets can be formed from several materials, but the choice must be compatible with the roof assembly. Tapered insulation is frequently used on low-slope roofs to create a designed slope without changing the structural deck. Depending on the system, the tapered package may include crickets, saddles, sumps, and transition pieces.
Other assemblies may use lightweight insulating concrete, wood framing, or another approved substrate. Structural design matters when added materials affect dead load, attachment, or the roof deck. A roofing contractor should not assume that an existing deck can support a proposed build-up.
The roofing membrane or covering must continue over the cricket in a way that is approved for the system. Membrane types differ in how they handle seams, corners, flashing, and movement. Materials that are incompatible with one another can compromise adhesion or durability, so specifications should identify approved components.
Design and Installation Considerations
Plan the Full Drainage Route
Before installing a cricket, determine where water will go after it passes the obstruction. The route should lead to an adequate drain, scupper, gutter, or roof edge. Avoid redirecting water into a dead-end area, toward a roof opening, or into a location where it can collect again.
Coordinate Heights and Transitions
Cricket elevations must work with the roof’s drain locations, curbs, parapets, and insulation thickness. Transitions should be gradual enough for the selected roofing system and should not create an unintended dam. Drain strainers, overflow drains, and access needs should remain clear.
Integrate Flashing and Membrane Details
Waterproofing is as important as the slope. The membrane must be installed continuously over the cricket and properly integrated with the flashing at the obstruction. Corners, seams, terminations, and changes in plane are common places to follow the manufacturer’s specific detail rather than improvise in the field.
Verify the Finished Surface
After installation, the roof should be checked for positive drainage, smooth transitions, open drainage paths, and signs of reverse slope. A visual review can identify obvious defects, but it does not replace required inspections or manufacturer-approved quality checks.
Common Flat Roof Cricket Problems
- Cricket too small: Water may still collect behind a wide obstruction or bypass the intended diversion.
- Wrong direction: A cricket may send water toward a wall, drain blockage, or another low spot.
- Insufficient or inconsistent slope: Dips and flat sections can undermine the intended drainage path.
- Poor flashing integration: A well-shaped cricket can still leak if its membrane and flashing details are defective.
- Blocked outlets: Debris in drains or scuppers can cause water to back up, even when the cricket is correctly built.
- Unplanned repairs: Adding material over an existing roof without checking compatibility, load, and drainage can create new problems.
Some water may remain temporarily after rainfall, depending on the roof’s design, weather, and drainage conditions. However, persistent ponding or recurring leaks warrant investigation by a qualified roofing professional. The underlying cause could involve a cricket, roof deflection, blocked drainage, membrane damage, or a combination of issues.
How to Calculate a Basic Cricket Rise
A simple rise estimate uses the chosen slope multiplied by the horizontal run. For example, if a design calls for 1/4 inch per foot over a 6-foot run, the rise is 1.5 inches: 1/4 inch × 6 feet = 1.5 inches. This calculation helps explain the geometry but does not establish the correct slope, cricket shape, or attachment method for a particular roof.
Real crickets often have two sloping faces and a ridge, so their dimensions require a plan view as well as a section. The run on each side may differ, and the cricket may need to connect to a drain or roof edge at a specific elevation. Tapered insulation layouts should show piece locations, thicknesses, and transitions clearly.
Code, Plans, and Professional Review
U.S. building codes are adopted and amended by state and local jurisdictions. Requirements can vary by building type, occupancy, climate, roof system, and the edition in force. Code provisions may address roof drainage, overflow drainage, structural loading, and roof covering installation, but they do not create one universal cricket detail suitable for every roof.
For new construction or a substantial reroof, the approved plans and specifications should define drainage direction, slope, cricket geometry, materials, and flashing details. A licensed design professional may be needed to address structural or code questions. Roofing contractors should follow the applicable plans and the membrane manufacturer’s installation instructions.
For an existing roof with standing water, an inspection can establish whether the issue is a missing or inadequate cricket, a blocked outlet, deck deflection, or another defect. Correcting the cause is more reliable than adding an improvised wedge or coating over the problem.
Maintenance Tips
Routine roof inspections help keep drainage paths clear. Property owners and facility managers should arrange inspections at intervals appropriate to the roof system and after severe weather, while following safe access procedures. Roof work can involve fall hazards and should be handled by trained personnel.
- Remove leaves and debris from drains, scuppers, and areas behind obstructions.
- Look for displaced membrane, open seams, damaged flashing, or cracks near cricket transitions.
- Check for recurring water accumulation and document its location and duration.
- Have suspected leaks or structural deflection evaluated promptly.
- Avoid cutting, fastening, or coating the roof without confirming system compatibility.
Frequently Asked Questions
Is a cricket required on every flat roof?
No. A cricket is typically used where an obstruction interrupts drainage and water could collect behind it. Whether one is required depends on the roof layout, project specifications, applicable code, and roofing system.
Can a flat roof cricket be added to an existing roof?
Often, but the repair must account for the existing membrane, insulation, structural capacity, drainage elevations, and manufacturer requirements. A professional assessment can determine whether an overlay or a larger roof repair is appropriate.
Does a steeper cricket always drain better?
Not necessarily. Slope is only one part of the design. The cricket must be correctly sized, smoothly integrated, waterproofed, and connected to an outlet that can handle runoff. An overly abrupt shape may also create installation or flashing problems.
What is the difference between a cricket and tapered insulation?
Tapered insulation is a material system used to create slope across a roof or in a localized area. A cricket is a drainage shape or feature. Tapered insulation can be used to build a cricket, but the terms do not mean the same thing.