Using shims to create a slope for a pergola cover serves several purposes:
Water Drainage: A sloped cover allows rainwater to run off rather than pooling on top of the pergola. This also helps to keep the cover clean.
Prevention of Debris Buildup: A sloped cover helps prevent debris like leaves or branches from accumulating on top of the pergola which can be unsightly.
Aesthetics: A sloped cover can enhance the visual appeal of the pergola, giving it a more finished and professional appearance. Shims can be created to fit any pergola, regardless the size or shape.
When using shims to create the slope, it’s important to ensure that they are properly installed and secured to maintain the desired angle and prevent shifting over time. The most common type of the shim used is the door stop. The other type is lateral which is more expensive, but the shims are hidden above the shade slats, so customers like the look of it better. Following are illustrations and instructions for both methods of creating and installing shims on a pergola prior to installation of our covers.
Board Dimensions (Based on pergola length):
12′ and less: Use a 2″x4″ board
12′ to 20′: Use a 2″x6″ board
Over 20′: Use a 2″x8″ board
How do lateral shims work? Like shade slats/purlins, lateral shims will run perpendicular to your rafters to add the desired slope required per the system of choosing by decreasing in height. The lateral shims can go on top of your current shade slats (if in good condition) or can replace your shade slats. Lateral shims are typically spaced every 24″- 30″ apart.
Below is an example of an 8′ L x 16′ W pergola with lateral shims every 24″ apart. (Prepped for Hercules system installation)
How to calculate how many lateral shims you’ll need: (Length of structure/divided by 2) Plus 1 For example, you would calculate the 8’L x 16’W structure above like: (8 / 2) = 4 4 + 1 = 5 lateral shims
*REMEMBER* The Hercules system requires a minimum slope of .25″ per 12″ to be watertight and in warranty.
How do lateral shims work? Like shade slats/purlins, lateral shims will run perpendicular to your rafters to add the desired slope required per the system of choosing by decreasing in height. The lateral shims can go on top of your current shade slats (if in good condition) or can replace your shade slats. Lateral shims are typically spaced every 24″- 30″ apart.
Below is an example of an 8′ L x 16′ W pergola with lateral shims every 24″ apart. (Prepped for Apollo system installation)
How to calculate how many lateral shims you’ll need: (Length of structure/divided by 2) Plus 1 For example, you would calculate the 8′ L x 16′ W structure above like: (8 / 2) = 4 4 + 1 = 5 lateral shims
*REMEMBER* The Apollo system requires a minimum slope of .5″ per 12″ for warranty.
Using shims to create a sloped pergola cover offers benefits like water drainage, debris prevention, and improved aesthetics. It’s important to correctly install and secure the shims to maintain the desired angle. Shims can be cut and attached in different ways depending on the system used (Hercules or Apollo). The minimum slope required varies for each system. For more information or advice on this, contact us to talk with a rep.
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