The mastic asphalt used for laying wood-block floors is suplied in blocks weighing 1/2cwt. each. A concrete foundation for the floor should be provided, and this should be brought to a true surface with a skin of neat cement. The asphalt is heated in an iron cauldron with sufficient bitumen to bring it to a proper consistency, and the blocks are dipped, into the heated mixture one by one as they are laid. Sometimes a mixture of pitch and creosote oil is used instead of mastic. Such work as this is usually done by specially experienced workmen.

The blocks are often grooved along the sides as shown in the accompanying illustration, and the asphalt entering into this groove keys them together and prevents them from rising.

Wood-block Floor laid with Mastic Asphalt.