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Foundation - Wood Block

sand, stringers and thick

FOUNDATION - WOOD BLOCK The blocks are sometimes set meetly upon the native soil, after it has been properly shaped and rolled; and sometimes upon a layer of sand.

The usual and best foundation is constructed by spreading a layer of coarse sand, about 3 inches thick, upon the prepared sub grade. Boards, 1 inch thick and 8 to 12 inches wide, are then laid lengthwise of the street from curb to curb, usually 8 feet apart, and are carefully bedded in the sand to the true cross section of the road way. These boards are to support the ends of the planks which form the foundation for the blocks. After the stringers are in place and well tamped, a straight edge or scraper reaching from one stringer to another is drawn from one side of the street to the other, thus leveling the sand flush with the top of the stringers.

If the sand is damp, it should be compacted by ramming. It is well to leave the sand a little higher than the stringers, in order to be sure that the foundation boards have a perfect support upon the sand throughout their entire surface. Sand can easily be fitted to the true surface, while it would be almost impossible to grade clay or loam as evenly. The sand also assists in draining away

any water which percolates through the paving.

On the stringers and the sand, the foundation planks are laid close together, across the street, the ends abutting on the stringers. These planks should be a fair quality of well seasoned lumber; and are usually 1 inch thick, but occasionally 2 inches thick, and sometimes are coated with hot tar. If the board is well seasoned and perfectly dry, the coal tar will increase the durability of the material; but if there is any sap or any moisture in the lum ber, the coal tar would effectually seal it up and hasten dry rot on the inside.

Round blocks are occasionally laid upon a concrete foundation, but such construction is not advisable under ordinary conditions. Round wood-block pavements are justifiable only where low first cost is absolutely necessary, in which case a concrete foundation is inappropriate.