Some kinds of lime, when slaked, leave a residue of stones and gravel and when this is the case instead of the mortar being mixed in the same box in which the lime slaked, the mix ture is thinned with water and is run through a fine seive into another box in which the mortar is mixed. If Rock land lime is used as is specified in our case, this will not be necessary.
Sand. The sand used, should be sharp and free from dirt, loam or other impurities. To obtain this, it is generally necessary to screen the sand. For our purpose a rather coarse sand will make the strongest mortar. The sand must be carefully inspected and in case of any doubt should be tested for purity. One test is by putting a handful into a dish of water, when any dirt or impurities will at once rise to the top as the sand sinks. Another test is to squeeze a handful of wet sand, and, upon opening the hand, if the sand retains its shape and soils the hand, it probably contains loam or clay and should be rejected. If. it falls down loosely without staining it is probably clean and good. The presence of fine loam in the sand will make the mortar work more easily- and it is sometimes so used by unscrupulous builders.
Cement. There are many brands of Rosendalc cement, which is the kind called for, and they are so welI known that for ordinary purposes it is only necessary to see that the casks bear the name of the specified brand, and that the cement is fresh and has not become crusty from absorbing moisture. The darker colors also indicate the better qualities. In case of any doubt, a simple test is to make two cakes of about a handful each mixed with a little water and allow one to set in the air, while the other is put to set in water. If the cement dries in the air with a light color and free from cracks, and sets under water with a darker color and without cracks, it is of a good qual ity; but if either cake cracks or becomes twisted and bub bly it shows a quality of cement which is inferior, and should be rejected. Cement must be kept in a dry place as a little moisture will cause it to set and it will soon be come worthless.
Cellar Wall. ZTpon our next visit, we find that the trenches all around the cellar have been filled and a portion of wall laid starting from the corner and running some ten feet in either direction. Our first care is to examine the lines by which the work is being laid up. We note that each line is tied to its proper notch on the batter boards and that the men are working to plumb lines hanging at intcrva]s from the long lines (See Fig..7), using the stones about as they come to hand, the only preparation being to square the too irregular ones, to niake a face on them by the use of the stone hammer. We tion the mason to level off the wall about every two feet (Fig. 15) and to keep the horizontal joints as near to a level as possible. We also call his attention to the clause in the specifications which calls for a bond stone in every ten square feet of wall, and carefully examine the wall already built to see if this has been clone. In a wall such as we require, that is, with practically two faces, there is often a tendency to build the two faces with long narrow stones and fill in between with small stones which are put in nearly dry with a little mortar on top to show well. Such a wall has an appearance of strength on the faces, but under a heavy load may fail from lacking of bonding. To detect this defect in a wall already built, and before the mortar has set, a very useful instrument is a steel rod about in diameter and four feet long. This will show at once, by being thrust down into the center of the wall, whether the stones are laid to overlap each other or not, and also if the stones in the center are well bedded or not, as they will rock and jar when struck with the rod if not bedded thoroughly. No stone should be set with a depth from the
face of less than six inches, and all stones should be laid so that their split surface is horizontal and breaking joints in the length of the wall, as well as through and through, and all angles should be bonded alternately, using the largest stones for the corners. (Fig. 16.) The corner which has been built, we find to be well bonded, as the first corner of any wall is apt to be when stones are plenty and near at hand (it is the last corner of a cellar wall which will need the sharpest watching), but about six feet from the corner we discover a line of vertical joints which runs irregularly but continuously, through four or five courses. (A, Fig. 17.) We call the man who is working upon this part of the wall, and point out the defect to him Ivith in structions to take down the wall until he can bond over the second course, and we caution the foreman to watch sharply against this sort of construction. Another bad practice which some masons encourage, is that of filling the spaces between the larger stones with chips or pebbles, in dry, and then smeared over with mortar which is more or less carefully worked into the seams. This kind of work will be easily detected by use of the steel rod, which we can feel mov ing the stones if poorly bedded. The right way is to settle each stone, no matter how small, into a becl of mortar either by rubbing with the fingers or by tapping with the trowel or hammer. In heavy work all large stones should be set with a derrick, as in rolling the stones up to their places on planks set up against the freshly laid wall, there is not only danger of shoving the wall out of plumb, but the bed of chips and mortar which has been prepared is sure to be tom up, and there is no certainty that the stones are properly bedded. Satisfied with the work which has been clone so far, we give orders that the filling in against walls be clone with coarse gravel or broken stone well pucldled with water or settled by ramming.
Underpinning. The next visit finds the cellar wall completed up to grade and the excavation filled in to the natural level of the ground. While we have no reason to suspect that our instructions have not been followed in regard to facing the wall on both sides, we nevertheless have recourse to the steel rod. Thrusting it down alongside the wall at intervals we do not find any projecting stones, and as the digging away of the filling in several places shows that the wall is properly cemented on the outside we feel reasonably sure that the wall is built according to contract, and proceed to a consideration of the underpinning, the portion of the cellar wall above ground, which being visible, must be considered from the point of appearance as well as strength. A variety of materials may be used for under pinning. Long pieces of granite or freestone in one or more courses are often used, sometimes an eight-inch brick wall is built upon the stone of cellar and often the cellar wall is continued up to sill of the same character as below ground, except that instead of being careful to fill the face joints, they are left without mortar for about three quarters of an inch in depth from surface, to be filled later with Portland cement mortar, colored to taste, and rubbed with a tool made for the purpose to give either concave, V-shaped, or raised joint.
It is important to see that the underpinning is carried up to the sill the full thickness of the wall, leaving out spaces for girders, with the top carefully levelled off at the bottom of the sill.