9910046 RevG April 2021
Appendix C: Ballast Blocks
PanelClaw does not provide the ballast blocks required to construct the system in accordance with
PanelClaw’s
Racking Construction Set
drawings. However, PanelClaw maintains a list of potential block suppliers across the country and this list is available upon request.
Ballast blocks for any ballasted rooftop system shall conform to ASTM C1491 or C1884 where applicable. Under these standards, ballast blocks
MUST
be manufactured and tested for freeze-thaw durability. In locations where the quantity of freeze-thaw cycles is less than 25 (see figure
below), ASTM C90 standard ballast blocks may be used. Please note the additional block specifications below which may be more stringent than
the ASTM specification. It is strongly recommended that installers weigh several blocks on-site to ensure block weights match what is it specified
on
PanelClaw’s
Racking Construction drawings.
PAGE
22
Ballast Block Description
Nominal Weight* lb [kg]
BLOCK, CONCRETE, 2"X 8"X 16"
14.6 [6.6]
BLOCK, CONCRETE, 3"X 8"X 16"
23.6 [10.7]
BLOCK, CONCRETE, 4"X 8"X 16"
32.6 [14.8]
*Tolerance = ± 5% Nominal Weight
Approximate Number of Freeze-Thaw Cycles Per Year
Minimum Ballast Block Specification
ASTM Standard
C1491 & C1884
C90
Min. Compressive Strength
2500 psi
2000 psi
Min. Density
125 pcf
125 pcf
Min. Water Absorption
13 psf
13 psf
