For inner dead air spaces, 2 × 6 inches × 40 feet studding are placed upright 12 feet apart, and horizontal cross studs 2 × 6 inches × 12 feet and three feet apart, are filled in between. This makes spaces 3 × 12 feet on the inside of all the outer walls.
Plates on the outer walls are 3 × 10, and on inner walls 3 × 8 inches.
The main studding is lined on both sides with moisture-proof sheathing, and boarded up with matched lumber. The inclosed space is filled with non-conducting substance, usually sawdust or spent tan bark. The filling must be dry and packed tightly.
The inner 2 × 6 studding is lined with sheathing, and then boarded up with matched lumber. The joints of this studding should be made with care and the lumber selected, no crooked stock being used. Sealing up these joints with pitch adds to their efficiency, and also to the durability of the lumber.
The outer studding is covered with weather boarding or ship siding. Twelve inches at the bottom are left open and hinged covers swung over them, which can be opened or closed as ventilation requires.
FIG. 49. PLATE B. CROSS SECTION.
The interior walls have 4 × 8 inch × 40 feet posts, and 3 × 8 studding, which are boarded on either side with matched lumber and filled.
The lower section of these walls, to a height of ten to fifteen feet, is often left without filling, as it is more exposed to the ill effects of moisture, and requires renewal before the upper portion. This is more conveniently done where no filling is in the wall.
In the center of each room, on the end at which the ice cakes enter, an opening is left extending from the sills to the plate. As the house is filled with ice these openings are closed up. Boards are provided, when building, which will fit into place and make the walls at these openings, as near as practicable, the same as in other places. The middle section being filled and planked by the inner and outer air spaces.