The thickness of mortar joints varies according to the quality of the brick used. Pressed brick, with edges straight and true, only requires a joint one-eighth of an inch thick ; ordinary brick joints at from one-quarter to three-eighths of an inch; while common brick frequently have as much as five-eighths of an inch at the joint.
Stretchers are the bricks laid with their lengths in the direction of the length of the wall. Headers are the brick laid with their lengths across the wall. See Fig. 7.
All bricks, to be laid in dry weather, should be wetted before being used, in order to wash off any dust and to prevent too rapid absorption of the moisture of the mortar. Whenever new brick work is joined to old, the old work should be thoroughly wetted to insure proper adhesion. All foundation brickwork should be started well below the lowest frost line.
In the erection of brickwork, all the walls should rise at about the same rate; no part being carried more than three feet above the rest, or unequal settlement is likely to occur with the result that the wall soon shows signs of fracture, If it is not possible to carry all the walls up simul taneously, the portion first built should be"stepped back" rather than "toothed." See Fig. 7.
Fig. 7 shows the bond commonly used in brick work, with headers every sixth course.
Fig. 8 shows what is known as English bond. The plans show the method of laying the bricks in the two courses.
Fig. 9 shows the arrangement of bricks to form the Flemish bond. In this and also the English bond, particular care should be taken to keep each vertical joint in any one course directly over the corresponding vertical joint in the course next but one below. A neglect of this precaution detracts considerably from the appearance of the finished work.
Fig. 10 shows the construction of a hollow wall, which, with the same amount of material, is more stable than a solid wall and possesses many other advantages. It consists of two separate walls, with an airspace of four inches between them, tied together with bonding irons or "clips" every few feet. A wall of this kind prevents dampness from penetrating to the inside.
Fig. 11 shows a damp-proof course, marked D P., which should never be omitted in important
work. It consists of a layer of impervious material laid on the walls just above the ground and below the floor beams; its object being to prevent dampness from rising from the ground and getting into the building. Materials suitable for damp-proofing courses are : Asphalt, pitch, slate, damp-resisting paints and cements, or any material that does not allow moisture to pass through it.
In buildings having a cellar below the ground, this damp-proofing material is applied to the out side of the cellar walls from a little above the ground level, well down to the under side of the footing course. See Fig. 12.
Lime, Cement and Mortar This is a subject to which considerable space might well be devoted, but, as it is not the purpose of this series to go into the subject so deeply, only such information will be given as may be required in the ordinary erection of cottages and the smaller buildings.
All lime should be freshly burned and thor oughly slacked.
All cement should be finely ground and free from lumps.
All sand should be clean, sharp, free from loam and salt, properly screened and washed.
Lime mortar is usually composed of three parts of sand to one of lime, but two parts of sand to one of lime makes a much better material.
Lime.—Rosendale cement mortar is mixed one part of Rosendale cement, one part of lime and five parts of sand and should be well mixed before the water is added.
Lime.—Portland cement mortar is mixed one part of Portland cement, one part of lime and six parts of sand. All should be well mixed before the water is added.
Rosendale cement mortar is mixed one part of Rosendale cement to two parts of sand.
Portland cement mortar is mixed one part of Portland cement to three of sand, for ordinary use, and for important work one part of Portland cement to two of sand, thoroughly mixed dry, adding only enough water to render mortar of good working consistency.
A little lime should be added to cement mortar to be used in freezing weather. The mortar should not be made up in greater quantities than required for the work on hand, and no excess that may have been left over night should be used in any way.