Deadening. By deadening is meant the constructing of floors and partitions so that the passage of sound is reduced to a minimum. Figure 136 shows a method in which a weak mortar, or mineral wool, is the means of deadening a floor, the mortar being of the proportions of one of lime to seven or eight of sand, the hair being omitted altogether. If used in a partition, laths should be laid diagonally, as shown in Fig. 137, and plastered as described in the previous topic.

There are several varieties of sheathing paper or quilt upon the market which may be used, by spreading one or more layers upon the under floor, and laying the wearing floor upon it. While this is of some help, it does not give satisfactory results.

Fig. 136. - Deadening a Floor; Method 1.

Fig. 137. - Dead-Ening A Pahtition.

Another method of treating a floor is shown in Fig. 138, which is more expensive, but also more efficient than that described in Fig. 136, as the mineral wool is only about a sixth as heavy as the lime mortar. In this latter method, the 2" piece supporting the wearing floor should not be nailed to the under floor more than necessary, as a connection will thereby be formed which will impair the efficiency of the deadening. Several thicknesses of sheathing paper between the deadening and the under floor will aid a great deal.

Suggestive Exercises

86. Of what kinds of wood should laths be made? Why? Compare the efficiency of the two widths of laths. The economy. Illustrate the methods of joining laths at the inside corners. How should laths be laid over door studs? How should laths be treated which are laid upon a wide timber? How should the inside of a 12" brick outside wall be treated if it is to be plastered? Why?

87. How should outside plastered corners be treated? Describe and compare two other methods of finishing corners.

88. What are grounds used for? What are the common sizes of grounds?

89. What are the proportions of sand, lime, and hair used in making mortar? When should the hair be put in? Which is the kind of hair generally preferred? What kind of sand should be used in mortar? How can sand be tested for clay or loam? Is creek sand suitable for mortar? Should mortar be used as soon as it is made? Why? How should plastering be put on to insure that it will hold? Describe the different coats of three-coat work. Of two-coat work. What governs the thickness of the plastering? What is the carpenter's work in making the building ready for the plasterer? Compare lime plaster, and ready mixed plaster.

Fig. 138. - Deadening a Floor; Method 2.

90. Describe back plastering. What is the value of it to a house?

91. What is meant by deadening? Describe a method of deadening a floor. A partition. Describe the most efficient method of deadening a floor.