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Problems introduced during this stage are the most costly to correct. Questions answered in the article cover topics such as use of reinforcement, snow melting and radiant heating systems, slope for drainage, surface tolerance vacuum dewatering, etc. It is better to use wire reinforcement in concrete in such things as patios or wide expanses of concrete slabs even though nothing heavier than people use them. In patios and other slabs not subject to loads the reason for putting steel in the concrete is to hold concrete together in spite of settlement cracking and faulting. In residential construction it is uncommon for such slabs to be built on soil that has been properly compacted, and settlement may continue for a number of years. For satisfactory heat transmission there is some latitude in how deeply radiant heat pipes may be embedded. As the thickness of the concrete over the pipes increases, it will be necessary to increase the water temperature somewhat. Ferrous or copper pipe is generally used with 2 to 3 inches of concrete cover over the pipes and 2 inches under the pipes. In any case, the concrete should be in intimate contact with the pipes. The usual practice is to slope walks and drives one-fourth of an inch per foot of width for drainage. This can best be provided by simply setting the form higher on one side than on the other. In some areas where drainage to both sides permits, walks and drives built with a crown are desirable. For example, proper drainage for a 10 foot wide driveway can be established by providing about 1 inch crown from center to the edges.