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How to Mark Out a Solar Array Layout on a Roof

This guide outlines the process for transferring your solar array design onto a roof surface. Accurate marking ensures that rails and attachments are installed correctly the first time, preventing unnecessary holes in the roof.

Click HERE for a full PDF of this guide

Tools Required

• Lumber Crayons: Use "wet/dry" crayons (e.g., Nissen or similar). These are larger than standard crayons and designed for construction surfaces. Colors: Get an assortment. You will need a low-contrast color (close to the roof color) for initial marks and a high-contrast color (like yellow) for final marks. +2 Chalk Line: A standard reel with blue or red chalk.

• Tape Measure: For verifying panel and rail dimensions.

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Step 1: Mark the Rafters

The first step is to identify the structural support (rafters) underlying the roof material.

1. Locate Rafter Tails: Look underneath the eaves of the roof to find the rafter tails.
   
   

2. Transfer to Roof: Transfer this location onto the roof by making a mark on the shingles or tiles directly above the rafter tail.
   
   

3. Draw the Line: Follow the rafter path up to the ridge. Ensure your line is at a right angle to the eave edge. Mark the top near the ridge with a crayon.
   
   

4. Snap a Chalk Line: Use your chalk line to snap a straight line from the mark at the eaves to the mark at the ridge.
   
   

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Step 2: Mark Panel Corners (The "Draft" Phase)

Before installing hardware, outline the array to visualize its position.

• Panel Dimensions:

• Standard (60-cell): Approximately $40" \text{ wide} \times 65" \text{ tall}$.
  
  

• Large (72-cell): Approximately $40" \text{ wide} \times 79" \text{ tall}$.
  
  

• Initial Marking: Mark the corners of the outer frames using a crayon color that blends with the roof (e.g., purple on dark shingles).
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• Tip: Using a low-contrast color prevents unsightly "graffiti" if you need to adjust the layout. These marks typically wash off with rain.
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• Final Marking: Once the location is finalized, mark the corners again using a high-contrast color (like yellow) to prevent confusion during installation.
  
  

Warning: Do not use the same color for initial drafts and final marks. This frequently leads to installation errors.

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Step 3: Mark Rail Locations & Attachment Points

Solar rails must be positioned to support the panels at specific clamping zones.

1. Determine Rail Spacing

Rails should run horizontally across the rafters.

• 60-Cell Panels: Rails should hit the back of the frame 16 inches from the top and 16 inches from the bottom.
  
  

• 72-Cell Panels: Rails should hit the back of the frame 19 inches from the top and bottom.
  
  

2. Snap Rail Lines

Measure the appropriate distance (16" or 19") from your top and bottom panel corner marks. Snap a chalk line horizontally across the roof for each rail row.

3. Identify Attachment Points

The locations where your Rail Lines intersect with your Rafter Lines are your roof attachment points.

• Select Intersections: Choose intersections that fall inside the outer marks of the array to ensure attachments are hidden under the panels.
  
  

• Max Span: The maximum distance between attachments is generally 4 feet. If rafters are spaced wider, or at the ends of rails, use closer spacing.
  
  

• Circle the Targets: Draw a circle (in yellow/high-contrast) around the specific intersections where you will install attachments.
  
  

Pro Tip: Explicitly circling the correct intersections is crucial. It prevents the "rookie error" of drilling into the wrong intersection and having to patch a hole later.

Next Step: Once the valid intersections are circled, you are ready to install the roof attachments.

Click HERE for a full PDF of this guide