Direct Answer
The main difference between a roof cricket and a roof sump is how each component manages water on a commercial roof. A cricket is a raised, sloped structure that redirects water around an obstruction or toward a drainage point. A sump is a depressed area around a roof drain that helps collect water and direct it into the drain.
Both components support positive drainage on low-slope commercial roofs, including TPO, PVC, modified bitumen, and built-up roofing systems. When properly designed and installed, they help reduce unwanted water accumulation and the risks associated with prolonged ponding.
According to GAF’s guide to roof crickets, crickets redirect water around obstructions and toward drainage locations. GAF also describes tapered insulation and sump components as methods for directing water toward roof drains.
Who This Applies To
- Commercial property owners
- Property and facility managers
- Commercial roofing contractors
- General contractors and developers
- Building envelope consultants and roof observers
- Condominium and HOA boards responsible for roof maintenance
- Owners evaluating ponding water or drainage deficiencies
Not for: This guide explains the general functions of crickets and sumps. It does not replace project-specific roof drainage calculations, approved construction drawings, manufacturer instructions, or applicable building codes.
1. What Is a Roof Cricket?
A roof cricket is a raised, sloped section of the roof that changes the direction of water flow. It is commonly installed behind roof penetrations or obstructions, such as HVAC curbs, skylights, and walls, where water might otherwise collect.
On commercial low-slope roofs, crickets are often constructed using tapered insulation beneath the roofing membrane. Their slopes help redirect water toward drains or away from areas where water could accumulate.
Common locations include:
- Behind rooftop HVAC equipment
- Behind large roof penetrations
- Along parapet walls
- Between roof drains
- Near skylights and raised curbs
- In roof areas where the existing slope does not provide effective drainage
Example: An HVAC curb sits in the path of water flowing toward a drain. A cricket is installed on the uphill side of the curb, splitting the flow and directing water around the obstruction.
Learn more from GAF’s explanation of roof crickets.
2. What Is a Roof Sump?
A roof sump is a lowered area around a roof drain that helps water move toward the drain opening. It creates a local depression relative to the surrounding roof surface, helping prevent the drain from sitting above the surrounding drainage plane.
On low-slope commercial roofs, sumps may be formed using tapered insulation or other roof-system components appropriate to the approved design.
Common locations include:
- Around internal roof drains
- At designated drainage collection points
- Near areas where tapered insulation directs water toward a drain
- At drainage points on large commercial roof sections
Example: A commercial roof has a drain, but the surrounding surface is too high to direct water efficiently into the drain opening. A properly designed sump creates a lower collection area that helps guide water into the drain.
See GAF’s tapered insulation information for examples of tapered components used to improve roof drainage.
3. Cricket vs. Sump: Key Differences
| Feature | Roof Cricket | Roof Sump |
|---|---|---|
| Primary purpose | Redirects water around an obstruction or toward a drainage point | Collects and directs water toward a roof drain |
| General shape | Raised, sloped structure | Depressed or lowered area |
| Typical location | Behind curbs, near walls, or between drains | Immediately around a roof drain |
| Water movement | Splits or redirects the flow | Concentrates flow toward the drain |
| Common construction | Tapered insulation or a constructed sloped assembly | Tapered insulation or a designed depressed drainage area |
| Primary drainage concern | Water trapped behind an obstruction | Water failing to reach or enter the drain efficiently |
| Typical benefit | Improves water flow around obstructions | Improves local drainage into the drain |
The simplest way to remember the difference is that a cricket redirects water, while a sump helps collect water at the drain.
4. Can a Commercial Roof Have Both?
Yes. Crickets and sumps can work together as parts of one drainage design.
For example, a large commercial roof may have a cricket that directs water away from an HVAC curb and toward a roof drain. A sump around that drain then helps collect the redirected water and guide it into the drain opening.
The components serve different functions, but they can complement each other.
For more information about drainage design, see GAF’s overview of single-ply roofing assemblies, which discusses the role of tapered insulation and crickets in directing water toward drains.
5. Why Do Crickets Matter on Commercial Roofs?
Crickets help address areas where the roof’s natural slope or drainage layout may allow water to collect behind obstructions.
They can help:
- Redirect water around rooftop equipment
- Reduce water accumulation behind curbs and walls
- Improve the drainage path toward roof drains
- Reduce debris accumulation in certain obstructed areas
- Help protect vulnerable roof transitions from prolonged water exposure
However, a cricket must be appropriately designed and integrated with the roofing membrane and flashing. An incorrectly constructed cricket can create new drainage problems instead of solving existing ones.
6. Why Do Sum ps Matter on Commercial Roofs?
Roof sumps help create a drainage collection point around roof drains. Without a properly formed drainage area, the drain may not receive water efficiently from the surrounding roof surface.
Depending on the roof design, sumps can help:
- Direct water toward internal roof drains
- Improve local drainage around drain openings
- Reduce water accumulation immediately around drains
- Support the drainage layout formed by tapered insulation
- Help achieve the intended roof drainage design
A sump cannot compensate for every drainage problem. An undersized or blocked drain, inadequate drainage capacity, insufficient roof slope, or downstream obstruction may still cause water accumulation.
For additional technical context, consult GAF’s tapered polyiso insulation guidance.
7. What Happens When Crickets or Sum ps Are Missing or Incorrectly Installed?
Missing or poorly designed drainage components may contribute to water accumulation, depending on the roof’s layout and drainage requirements.
Potential problems include:
- Persistent ponding water
- Water collecting behind rooftop equipment
- Slow drainage around roof drains
- Debris accumulating in low areas
- Prolonged moisture exposure around roof details
- Premature deterioration of roofing materials
- Leaks where water reaches defective seams or flashing
Not every roof requires a cricket at every obstruction or a sump at every drain in the same configuration. The appropriate design depends on the roof geometry, drainage layout, system requirements, and applicable codes.
8. How Should Property Owners Identify a Drainage Problem?
Property managers should look for evidence that water is not following the intended drainage path.
During a professional inspection, the following should be evaluated:
- Water accumulation behind curbs or equipment
- Standing water around internal roof drains
- Debris collecting in low areas
- Evidence of repeated ponding
- Damaged or poorly integrated roof membrane
- Flashing defects near drains and obstructions
- Blocked drain strainers or outlets
- Differences between the installed roof slope and approved drainage plans
Photographs and roof plans can help document the location of each issue. If the problem is persistent, a qualified commercial roofing professional should evaluate the drainage layout and determine whether corrective work is necessary.
Related guidance: How Is Ponding Water Assessed on a Flat Commercial Roof and When Is It a Problem?
9. Can Crickets and Sum ps Solve Ponding Water?
They can help when the problem is related to the roof’s slope or the way water is directed toward a drainage point. However, they are not universal fixes for ponding water.
Before recommending corrective work, the roofing professional should determine whether the underlying cause is:
- Inadequate or incorrectly formed slope
- A poorly positioned drain
- A blocked or damaged drain
- Roof-deck deflection or settlement
- An obstruction in the drainage path
- A combination of drainage and membrane deficiencies
The solution should address the actual cause. Adding a cricket or sump without evaluating the existing drainage system may not resolve the problem.
10. What Should Owners Ask Their Roofing Contractor?
When a drainage issue is identified, owners should ask:
- Is the water accumulation caused by roof geometry, a blocked drain, or another problem?
- Would a cricket improve the flow around an obstruction?
- Does the roof drain need a properly formed sump?
- Are the existing drains and outlets functioning correctly?
- Will the proposed work integrate with the existing roofing membrane?
- Does the work require revised drawings, permits, or engineering review?
- How will the contractor verify that the corrected area drains properly?
- What photographs and completion records will be provided?
These questions help owners distinguish routine drain maintenance from a roof-design issue that may require more extensive corrective work.
Bottom Line
A roof cricket redirects water around obstructions or toward drainage points, while a roof sump creates a lowered collection area that helps direct water into a roof drain. Both may be used together to improve drainage on commercial low-slope roofs.
If a roof has persistent ponding, the owner should not assume that adding either component will automatically solve the problem. The drainage path, drain capacity, roof slope, and condition of the existing roof system should be evaluated before corrective work is selected.
Related Questions
- How Is Ponding Water Assessed on a Flat Commercial Roof and When Is It a Problem?
- What Should You Do When an Underwriting Inspection Flags Roof Debris or Drainage Problems?
- How Often Should Commercial Roofs Be Inspected in Florida?
Sources
- GAF — What Is a Roof Cricket?
- GAF — EnergyGuard Tapered Polyiso Foam Insulation
- GAF — Understanding the Layers of a Single-Ply Roofing Assembly
- GAF — Built-Up Roofing Systems Design and Application Guidance
Last reviewed: October 2026
Related Resources
Commercial Roof Ponding Water Assessment
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Disclaimer: This information is provided for general educational purposes and is not engineering, architectural, building-code, or roofing-design advice. Actual drainage requirements depend on the roof system, approved design, manufacturer instructions, and applicable local codes. Consult a qualified commercial roofing professional or design professional for project-specific recommendations.
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