a very wet mixture of gravel, sand, and cement into iron moulds having the form of a house, and after the removal of the forms or moulds, leave standing a complete house with a fine surface, plain or ornamental, all in one solid piece, including the cellar, partitions, floors, roof, stairs, mantels, veranda-in fact everything except the windows and doors, which are of wood and the only parts of the house that are combustible.

"The house is to be heated by boiler and radiators in the usual manner, the plumbing to be open and jointed by electric welding.

"The experimental house has the partitions arranged to give, besides the cellar, two rooms on first story (one to be used as a living room and the other for a kitchen); the second story to have two rooms and bath; the roof story to have two rooms. When large numbers of houses are made, the partitions can be changed to make more rooms. Once the house is cast, however, no changes can ever be made-nothing but dynamite could be used to remove a partition without great expense.

"With a few simple additions to the iron forms, a great many variations in the type of the houses can be made. For instance, by adding or subtracting iron sections, the house can be made. smaller and cheaper. By adding sections, the number of stories can be increased, or it can be widened or lengthened. By a few additional forms, the whole appearance of the veranda can be changed. A contracting company having the smallest unit possible to permit of cheap and rapid production, must have six sets of moulds with the other necessary machinery. From these iron sections almost any variation in the size, appearance, and ornamentation of the row of houses can be made. The concrete could be tinted with any kind of color, but the general type would be the same. The units might be divided and thereby three complete moulds for one type of house and three sets for an entirely different type, would be secured.

"This scheme of constructing houses cheaply and in quantities does not permit of the building of one house at a time, for the reason that the moulds are heavy. The machinery necessary to handle the materials as well as for the erection of the iron moulds, is large and expensive.

"The hardening of the cement requires four days. While one house was hardening the men would either have to remain idle or be laid off during this period, and this would not be practicable; whereas, if the full unit of a minimum of six sets of moulds, and machinery was in operation, the thirty-seven men necessary could be employed continuously erecting, pouring, and removing forms from one lot to another, at a minimum of expense.

"Houses of this type, I believe, can be built for $1,200 each, in any community where material excavated from the cellar is sand and gravel, so it can be used. If the sand and gravel must be obtained elsewhere, the cost will be much more. A change in the forms can be made so that a house can be built that will look just as well, but smaller, at a less cost. On the other hand, by addition to the forms, houses costing $2,000 or $3,000 or more can be built. "To give a rough idea of the cost, I estimate that six sets of iron forms for the house I am to build will cost about $25,000 per house -a total cost of $150,000. The cranes, traction steam shovel, conveying and hoisting machinery, I estimate, will cost $25,000 additional, making a total investment of $175,000. With this machinery twelve (12) houses per month can be made every month in the year, with the aid of one foreman, one engineer, and thirtyfive (35) laborers. This gives one hundred and forty-four (144) houses per year for the unit. If I can prove this, then the labor cost per house will not exceed $150 each.

"If we allow 6 per cent interest and 4 per cent for breakage on the cost of the forms, and 6 per cent interest with 15 per cent depreciation on machinery, the yearly expense will be about $20,000. Dividing this into the 144 houses built in the year, gives approximately $140 per house, for cost of moulds and machinery. 220 barrels of cement will be mixed with the sand and gravel excavated from the cellar, and will provide sufficient material to build the house. Allowing $1.40 per barrel for cement, adds a further sum of $310. The reinforcing steel rods cost $125; and the heating system and bath $150. These items total $875. This leaves a margin between that sum and $1,200 of $325 to provide for doors, windows, etc., painting, and the correction of any possible defects.

"If the houses are smaller and 225 can be built in the year for the same investment and labor, it will, from the above data, be

easy to approximate the cost per house; the same is true with larger size houses.

"These houses will be waterproof and dampproof. The roofs, after the forms are removed, are painted with a paint made of cement tinted with red oxide of iron, which hardens and never deteriorates. Cement can be tinted to any color and any shade of that color, and the inside or outside can be painted, and is permanent. The cost of the paint for the whole house, inside and out, including roof, will be very small.

"Should the experiment succeed, I will, without cost, furnish all plans, give full license to reputable building corporations without cost, as I am not making these experiments for money.

"I think the age of concrete has started and I believe I can prove that the most beautiful houses that our architects can conceive can be cast in one operation in iron forms at a cost, which by comparison with present methods, will be surprising. Then even the poorest man among us will be enabled to own a home of his owna home that will last for centuries with no cost for insurance or repairs, and be as exchangeable for other property as a United. States Bond."

The following table, compiled by the National Fireproofing Co., gives a good idea of the comparative cost of various classes of residences.

COMPARATIVE COST OF VARIOUS TYPES OF RESIDENCES. (A $10,000 frame residence is taken as a unit.)

Hollow terra cotta blocks, stuccoed, fireproof throughout, except roof.

12,000

Hollow terra cotta blacks faced with brick, fireproof floors.

14,000

Brick walls, fireproof floors.

15,000

Houses can be built with terra cotta blocks for walls and floors with wooden roofs at a cost of twenty-two cents per cubic foot; if built with wooden floors and roof, at eighteen cents per cubic foot.

CHAPTER XI

MORTARS, PLASTERS, AND STUCCOS, AND HOW TO USE THEM

The Art of Stuccoing.-Lime Mortars and Plasters.-Interior Plasters and Plastering. -Gypsum Plasters.-Portland Cement Plasters or Stucco.-Exterior Lathing and Plastering. Application of Stucco to Stone.-Stucco on Brick.-Stucco on Concrete.-Quantities of Materials for Stucco.

THE art of using mortars is as old as civilization; the pyramids of Egypt contain plaster work executed at least four thousand years ago; very early in Greek architecture a true lime stucco of thin white composition was employed as a ground on which to paint their decorative ornament; the Romans were familiar not only with lime and plaster, but with hydraulic cement as well.

There is every reason to believe that originally these stuccoes were intended to cover up and protect inferior building stone and sunburned straw brick. The archæology of stucco would tend to show that from an artistic standpoint this method of decoration was a development of the wattled buildings, which were plastered with clay and different muds hardened by being baked in the heat of the sun. Therefore, in this instance, the use of clay plaster over wattled houses was to protect an inferior building material.

At the present time, mortars and plasters are among the most familiar materials employed by the builder. These consist of three general classes, which, however, grade into each other when mixed in different proportions:

1. Lime plasters.

2. Gypsum plasters.

3. Portland cement plasters or stucco.

Lime is used for interior plastering where the walls are to be papered; gypsum or plaster of Paris, where a white or hard surface is desired; and Portland cement mortar for exteriors where strength. and durability are required.

Lime Mortars and Plasters.-As already explained in Chapter II, lime is produced by heating a pure or nearly pure limestone in a

kiln to such a temperature as will drive off the carbonic acid gas and leave calcium oxide or "quick lime." When water is added to quick lime it changes from a lumpy condition to a soft, impalpable powder known as "slaked lime." When more water is added, the slaked lime becomes a paste, and this paste is mixed with sand to form a mortar.

Mortar for plaster work is usually composed of slaked lime, mixed with sand and hair. The sand should be hard, sharp, gritty, and free from all organic matter. Pit sand is generally sharp and angular and is preferable to river and sea sands, which are more rounded and are apt to contain saline particles that may cause efflorescence.

Hair is used as a binding medium to increase the cohesion and tenacity. Good hair should be long, strong, and free from grease or other impurities.. Ox hair is generally used, although sometimes adulterated with the short hair of horses. Substitutes for hair include manila fibre and sawdust.

Interior Plastering.-Lime mortar, when used as a plaster for walls and ceilings, is placed preferably in three coats on wooden or metal laths. On brick or tile walls, and in residence construction two coats are often considered sufficient, and for rough plastering, one coat. Three-coat work makes a straight, smooth, strong, and sanitary surface for walls and ceilings when properly executed. The processes employed for the different coats are as follows:

1. Scratch coat.

2. Brown coat.

3. Finish.

First or Scratch Coat.-The first or scratch coat should be from 3/8 to 5/8 of an inch thick, composed of 1 part of lime paste to 2 of sand, and 1 bushel of hair to 2 of lime. The plaster should be stiff enough to cling and hold up when laid, yet sufficiently soft and plastic to go through the interstices between the laths, leaving a trowelful partly overlapping the previous one, the one binding the other.

Scratching consists in scoring the surface of the first coat to obtain a key for the following one. It is done with a wooden or iron scratch, which may have from one to five points. The first coat should be allowed to stand for an hour or two so as to allow