A piece of stone may have a stated size such as 12” wide x 24” long x 1” thick, but when the stone is measured, both the size and the thickness are different than stated. There is a simple explanation for this. Stone suppliers have traditionally used nominal dimensions.
NOMINAL DIMENSIONS
Nominal measurements (length x width) traditionally refer to the size of the stone without a grout joint. For example, in a natural cleft piece of 12”x24” bluestone, the actual size is cut smaller to allow for a grout joint when setting the stone.
Nominal measurements (thickness) traditionally refer to the average thickness of the stone. For example, 1” thick natural cleft flagging ranges in thickness from approximately ¾” to 1-¼” thick and 1-½” thick natural cleft flagging ranges in thickness from approximately 1-¼” to 2”.
ACTUAL DIMENSIONS
Actual measurements are the “true” final size of the stone.
Common Bluestone Dimensions
for Flamed Flagging *
+/- ⅛”
| Nominal Size | Actual Size* |
|---|---|
| 12" X 12" | 11-⅝” X 11-⅝” |
| 12" X 18" | 11-⅝” X 17-⅝” |
| 12" X 24" | 11-⅝” X 23-⅝” |
| 12" X 30" | 11-⅝” X 29-⅝” |
| 12" X 36" | 11-⅝” X 35-⅝” |
| 18" X 18" | 17-⅝” X 17-⅝” |
| 18" X 24" | 17-⅝” X 23-⅝” |
| 18" X 30" | 17-⅝” X 29-⅝” |
| 18" X 36" | 17-⅝” X 35-⅝” |
| 24" X 24" | 23-⅝” X 23-⅝” |
| 24" X 30" | 23-⅝” X 29-⅝” |
| 24" X 36" | 23-⅝” X 25-⅝” |
Common Bluestone Dimensions
for Natural Cleft Flagging**
+/- ¼”
| Nominal Size | Actual Size** |
|---|---|
| 12" X 12" | 11-½” X 11-½” |
| 12" X 18" | 11-½” X 17-½” |
| 12" X 24" | 11-½” X 23-½” |
| 12" X 30" | 11-½” X 29-½” |
| 12" X 36" | 11-½” X 35-½” |
| 18" X 18" | 17-½” X 17-½” |
| 18" X 24" | 17-½” X 23-½” |
| 18" X 30" | 17-½” X 29-½” |
| 18" X 36" | 17-½” X 35-½” |
| 24" X 24" | 23-½” X 23-½” |
| 24" X 30" | 23-½” X 29-½” |
| 24" X 36" | 23-½” X 25-½” |
