The importance of a cricket slope on a flat roof cannot be overstated for preventing ponding water and protecting roofing systems from premature failure. This guide explains what a cricket is, how to design slope, materials and installation best practices, common mistakes to avoid, code and cost considerations, and maintenance tips to ensure long-term performance. Correctly designed crickets channel water to drains or scuppers and extend roof life.
| Topic | Key Point |
|---|---|
| What Is A Cricket | Small saddle to divert water around penetrations or to drains |
| Slope Recommendations | Minimum 1/8″ to 1/4″ per foot; 1/2″ preferred for critical areas |
| Materials | Plywood/tapered insulation with membrane or preformed products |
| Common Issues | Ponding, inadequate slope, poor flashing, blocked drains |
What Is A Flat Roof Cricket And Why It Matters
A cricket, also called a saddle, is a small raised area built on a roof to divert water around roof obstructions or toward drainage points. On flat or low-slope roofs, crickets prevent ponding water that accelerates membrane deterioration. Proper diversion reduces leaks at chimneys, condensers, parapets, and large roof intersections.
When To Use A Cricket On A Flat Roof
Crickets are essential where two roof planes meet, behind parapet walls, around large penetrations, and upstream of roof drains. Any area that traps water or is adjacent to a critical penetration should be considered for a cricket. Local climate, roof pitch, and drainage layout influence whether a cricket is necessary.
Designing The Right Cricket Slope
Design begins with defining the target drain points and the cricket shape—typically triangular or trapezoidal. A minimum slope of 1/8″ per foot is commonly used, but 1/4″ to 1/2″ per foot is preferable for faster drainage. Steeper slopes reduce ponding risk but may require thicker tapered insulation or more framing.
Materials And Build-Up Options
Common cricket builds use tapered rigid insulation over roof deck, structural wood or metal framing with cover boards, or factory-made preformed crickets. Tapered polyiso insulation is popular for combining slope and insulation R-value in one assembly. The final layer is the roofing membrane—EPDM, TPO, PVC, modified bitumen, or built-up roof—sealed over the cricket.
Integrating the Cricket With Roofing Membranes
Membrane continuity and proper flashing are critical at cricket transitions. Seam integrity, adhesive compatibility, and mechanically fastened edges must be detailed to prevent leaks. For steep crickets, use coverboards and fasteners to stabilize the assembly before applying the membrane system.
Step-By-Step Installation Overview
Proper installation typically follows: survey and layout, install tapered insulation or framing, add cover board, install membrane and flashings, and inspect. Each step must ensure secure fastening, correct taper geometry, and continuous membrane laps at all transitions. Manufacturers’ details should guide membrane-specific procedures.
Layout And Framing
Mark cricket boundaries and centerline toward the drain. For wood decks, construct framing or nailers as needed. Ensure the cricket’s peak aligns to divert water evenly to intended drains.
Insulation And Cover Board
Install tapered insulation boards with staggered joints and proper adhesive or fasteners. Add a cover board if required by the membrane manufacturer. Seams should be staggered and installed to avoid thermal bridging and deflection.
Membrane Application And Flashing
Apply the roof membrane according to product specifications, integrating it seamlessly over the cricket. Flash penetrations and perimeter details with compatible materials. Heat-welded, fully adhered, or fully adhered with adhesive options each require specific sequencing to avoid wrinkles or voids.
Common Mistakes And How To Avoid Them
Poorly designed crickets often have insufficient slope, inadequate waterproofing, or improperly integrated flashings. Avoid cutting corners by verifying taper thickness, fastening schedules, and flashing compatibility before installation. Regularly inspect for ponding after storms during the first year to catch issues early.
Code, Warranty, And Manufacturer Considerations
Building codes and roof system warranties often require adherence to specific slope, insulation, and drainage guidelines. Consult local codes and the membrane manufacturer’s installation manual to ensure compliance and preserve warranty coverage. Some warranties are voided if manufacturer details are not followed exactly.
Maintenance And Inspection Best Practices
Regular inspections should check for ponding water, membrane blisters, seam separation, and debris near drains. Clear debris and verify that crickets divert water effectively after heavy rainfall. Seasonal checks and prompt repairs extend roof service life and prevent costly water damage.
Cost Factors And Budgeting
Costs depend on cricket size, materials (preformed vs. tapered insulation), labor complexity, and roof access. Tapered insulation crickets are cost-effective for large projects; preformed units can save labor on small or complex details. Include contingency for flashing upgrades and potential deck repairs uncovered during work.
Selecting A Contractor And Specifying Work
Choose contractors with flat-roof experience and references for cricket installations. Request shop drawings showing slope, insulation thickness, fastening pattern, and flashing details. Written specifications and manufacturer-approved details reduce risk and ensure correct execution.
Case Examples And Practical Applications
Common use cases include crickets behind parapet drains on commercial buildings, saddles at large rooftop equipment curbs, and tapered transition saddles at roof offsets. Well-designed crickets eliminated chronic ponding issues in retrofit projects by re-routing flow to existing drains without adding new penetrations.
Frequently Asked Questions
How Much Slope Is Required For A Cricket?
Minimum recommended slope is 1/8″ per foot; 1/4″ to 1/2″ per foot is better where feasible. Steeper slopes reduce maintenance and ponding risk.
Can A Cricket Be Added To An Existing Roof?
Yes, retrofits are common and typically use tapered insulation or framed saddles under a new membrane overlay. Assess the current deck condition to avoid hidden structural or moisture issues.
Are Preformed Crickets Worth The Cost?
Preformed crickets provide consistent slope and quick installation for small or intricate areas. They can be cost-effective where labor costs are high or geometry is complex.
Signs A Cricket Is Failing
Indicators include recurring ponding, membrane seam failures, water stains around penetrations, and increased interior leaks. Timely inspection and repair reduce secondary damage to decking and building interiors.
Tools And Materials Checklist
- Tapered polyiso insulation or preformed cricket units
- Cover boards and compatible fasteners
- Roof membrane chosen for the project (TPO, EPDM, PVC, etc.)
- Adhesives, primers, flashing materials, and sealants
- Layout tools, cutting tools, and safety equipment
Final Design Tips For Long-Term Performance
Preferably design crickets to shed water to multiple drains where possible, avoid dead-end pockets, and keep slopes smooth without abrupt changes. Document the cricket location and build-up in roof drawings for future maintenance and warranty claims.
For additional technical guidance, consult roofing material manufacturers’ technical bulletins and local building codes to ensure that cricket design, slope, and membrane details meet all performance and regulatory requirements.