Why Roof Pitch Matters
An RTU is designed to sit level. If it is installed on a sloped roof using a flat curb, several problems can occur:
Condensation and Drainage Issues
Rooftop units rely on gravity to drain condensation. When tilted, condensate can collect inside the unit instead of draining outward, potentially causing:
- Leaks into the building
- Internal rust or corrosion
- Damage to electrical and mechanical components
Weight Distribution and Safety
A roof curb is designed to distribute the weight of the RTU directly downward. If a flat curb is placed on an angled roof, the load is shifted unevenly across the curb. This alters the RTU’s center of gravity and can lead to:
- Structural stress on the curb
- Curb failure
- Risk of the RTU tipping or sliding, especially in wind or storm conditions
A properly leveled unit eliminates these issues and ensures safe, reliable operation.
Fixed Pitch Curbs
For sloped roofs, contractors often order a custom fixed pitch curb (also known as a welded pitch curb). This requires:
- Accurate measurement of the roof’s pitch
- Correct orientation of supply and return openings
- Ensuring the curb is manufactured to match that exact slope
Ordering fixed pitch curbs works well—when all measurements and orientation details are correct. However, mistakes or unknown variables can result in delays, additional costs, and incorrect curb orders.
Adjustable Pitch Curbs
An adjustable pitch curb eliminates the guesswork and provides flexibility on the job site.
Key features include:
- Ability to pitch in any direction
- Shipped knockdown for easy transport and assembly
- Adjustment up to 1 inch per 12 inches of roof slope in any direction
- Lower cost compared to welded fixed-pitch curbs
This design allows installers to level the curb directly on site without prior knowledge of exact pitch or rooftop unit orientation.
Benefits
- Reduces the number of curb types needed in inventory
- Improves installation flexibility
- Avoids delays caused by incorrect fixed-pitch orders
- Provides a reliable solution for roofs with multiple slopes or unit orientations
Adjustable Height: An Added Advantage
Beyond pitch adjustment, adjustable pitch curbs also function as adjustable height curbs.
Most manufacturers use standard curb heights—often around 14 inches. MicroMetl offers several fixed-height options (8″, 11″, 14″, and 24″), but requesting a non-standard height typically adds cost.
An adjustable pitch curb can help avoid those additional costs by allowing height variation based on installation needs. Because the curb is designed to compensate for up to a 1 in 12 pitch, the exact height range will vary depending on the curb’s length and configuration.
If you need assistance determining a specific height requirement, our MicroMetl Customer Service team is always available to help.
