34 Pa. Code § 21.64
The following woods shall not be less than 5% larger than spruce in each cross section dimension:
| Aspen | Populas tremuloides, grandidentata. |
| Basswood | Tilia glabra, heterophylla. |
| Buckeye | Aesculus octandra, glabra. |
| Butternut | Juglans cinerea. |
| Incense cedar | Libocedrus decurrens. |
| Western Red cedar | Thuja plicata. |
| Chestnut | Castanea dentata, pumila. |
| Cottonwood | Populas deltoides, deltoides virginiana, heterophylla, balsamifera, sargentii. |
| Black cottonwood | Populus trichocarpa, trichocarpa hastata, macdougalii, fremontii. |
| Eastern hemlock | Tsuga canadensis. |
| Lodgepole pine | Pinus contorta. |
| Northern white pine | Pinus strobus. |
| Ponderosa pine | Pinus pondersoa, Pinus jeffreyi, (Jeffrey Pine). |
| Sugar pine | Pinus lambertiana. |
This section cited in 34 Pa. Code § 21.21 (relating to wood side rails); and 34 Pa. Code § 21.65 (relating to wood for ladder use).