BALLAST - STRUCTURAL

BALLAST SYSTEM COMPONENTS

The following components are specific to the ballast racking system and at the time of this publication will need to be manually added to the BOM upon completing the engineering reports in Unirac for the ballast layout:

1. Bays:

   • Dimensions:

     • 15” wide (corresponds to spacing in aurora)

     • 5.5” on the lower edge

     • 11” on the higher edge

   • Tilt:

     • The difference in edge height from the higher to lower edge of the ballast bay results in a pitch of +10 degrees relative to the natural pitch of the roof.

2. Blocks:

   • Max of 4 per bay

   • If more blocks are needed, it will require additional bays

3. Clamps

PITCH

A Ballast System will be considered for:

• Roofs with a pitch of 5 degrees (1/12) or less.

• Flat roof membranes that are not the rolled variety regardless of pitch:

  • i.e. Tar & Gravel

A standard roof mounted racking system can be used when:

• Roofs are between 5-9.5 degrees (1/12-2/12) and of rolled membrane type:

  • Use simple grip mounts compatible with typical racking systems

• Roofs are 9.5 degrees (2/12) or greater should always be of shingle, tile, metal or other pitched roof compatible membrane type.

STRUCTURAL FRAMING

Ballast systems rely on ballast blocks to counter wind uplift rather than mounting directly into structural members. For this reason, the total structural load on the structure below can be a lot higher based on the ballast blocks depending on how the weight is distributed across the array. Here are the basic guidelines you should follow for your structural design:

1. Most flat roof types will fall into the vaulted conventional category.

   • This will usually require an alternative method of measurement to get the structural member size and spacing.

   • Surveyors will also be required to provide a Load Bearing Wall Sketch.

     • We still need to get an acceptable and fairly accurate span measurement for structural calculations.

     • Utilizing this drawing will help  you determine if the full span of the roof can be reduced or not based on load bearing walls breaking up the total load along the rafter.

2. We can choose traditional conventional/trusses only if we can prove there is accessible attic space with evidence of truss webbing (for truss roofs) or the presence of both rafter AND ceiling joists (for conventional framing)

READING A LOAD BEARING WALL SKETCH

Since we won't usually have the home schematics, we have to use some context clues to identify load bearing walls. Here are a few guidelines to use to identify them:

• • Interior walls running parallel with the joists/rafter direction will not be load bearing.

  • Interior walls running perpendicular to the joist/rafter direction are much more likely to be load bearing.

    • On a single level home, it's a little easier since there's only one wall level to worry about. 

    • It becomes more complex when there is more than one level on the home, as you would need to identify common walls all the way up the home vertically and it is possible for load bearing members following the same direction to be hidden such as a beam hidden in the framing.

In this particular example, the walls in green are the only walls that could possibly be load bearing.

• The roof section on the left has a wall on the interior center that is perpendicular to the direction of the rafters.

  • The span for this roof section can be halved

• The roof section on the right has a wall on the interior center as well, however, it is parallel with the direction of the rafters and therefor would not be considered a load bearing wall. 

  • The span for this roof section cannot be reduced.