1-coat work - Lath and lay or lath and plaster one coat. 2-coat work - Lath, lay and set, or lath and plaster and set. 3-coat work - Lath, plaster, float and set, or lath, lay, float and set. The first and second coats on walls and ceilings are put on with a steel trowel (see Fig. 258), the only difference being that the first coat on the ceiling is pricked up with a wooden pricker, which scores the plaster with lines, and forms a key for the second coat.

In places subjected to hard wear, as angles of chimney jambs, etc., and where a smooth, hard surface is required, Keene'sandPariancementscanbestrongly recommended. As the ordinary lime backing coats cannot be used, it is necessary under these circumstances to use cement and sand in the proportion of 1 to 2 put on in two coats, making a total thickness of 1/4 inch. The setting coat, about \ inch, is then put on with a wood float and worked to a smooth surface with a steel trowel.

Fibrous Plaster is now extensively used for covering ceilings and forming cornices. It is a preparation of plaster of Paris on canvas, from 1/2 inch thick, and sometimes strengthened by wood laths at the back. The slabs are sent out in sizes about 2 feet 6 inches by 3 feet, which are fixed to the ceilings and partitions with compo nails and washers or brass screws.

Cornices, mouldings, and casings for columns are made in a similar manner. They are delivered on the job in convenient lengths, and the joints made good with plaster of Paris modelled to match the existing moulding. This method is strongly recommended, as it is far cleaner than running cornices by hand.

Cornices are also run in situ. The ceiling and walls are bracketed out as required to fit the profile (see Fig. 259), and plaster of Paris put on to block them out to a rough outline, and the mouldings are run by a wooden "horse" (see Fig. 258), to which is attached a zinc profile of the cornice to be run. The horse is kept in position by a wood screed fixed at the bottom of the cornice and by a plaster screed on the ceiling.

On Lath 376

Fig. 258.

Cornices and enrichments are also cast in wax moulds in convenient lengths and afterwards bedded or screwed in position.

The most artistic work is modelled in situ, the plastic being gauged to retard its setting, but in most cases the cost precludes the use of this method.

Rough Cast is the name given to plastering on external walls when finished with rough pebbles, about •\ inch to \ inch sand or grit, mixed with lime or cement, and dashed on the second coat while still wet. If the finished surface is required to be white, chalk is mixed with the lime, or Russian tallow and copperas; but on no account should the rough cast, when dry, be lime-washed or coloured, or a very sticky appearance will result from the rain running down and carrying the colouring with it. If, however, any colour but white is required, the colouring matter should be mixed with the finishing coat.

Depeter

In this form of rough cast the gravel is pressed in by hand to patterns which may be formed by different coloured stones pressed in with a float.

Compo or cement rendering is the covering of large surfaces, such as the fronts of houses, with a mixture of Portland cement and sand. The joints of the brickwork are first raked out to a depth of \ inch, and the surface is hacked to form a good key for the first coat. For new work the external face of the wall should be built in rough stocks with protruding joints. The dust is next removed from the wall, which is then brushed down with a hard brush, and the surface wetted to assist the adhesion of the cement.

In new work the external face of the wall should be built in rough stocks with projecting joints. Rules, which are strips of wood about 1 inch thick, and projecting 1/2 to 3/4 inch in front of the wall, are next nailed to the vertical edges of the wall, and these will act as a guide for the thickness of the first coat.

Depeter 377

Fig. 259.

The wall is then spaced into bays of from 4 to 10 feet, and screeds, of the same material as the rendering coat, and equal in thickness to the projection of the rule, are then put on the wall and brought into line with the rules by means of a straight edge, and afterwards tested by stretching a line from end to end of the front to be composed.

In some cases nails are driven into the joints of the brickwork, and used in place of the screeds and tested in the usual way.

When the screeds are sufficiently hardened the walls between the screeds are rendered and brought to a face with a straight edge, working first from one rule to a screed and then from screed to screed along the face of the wall.

In most cases the face of the rendering coat is rough enough to receive the fining if suitable sand has been used. If, however, the sand has worked too smooth the face should be scraped with a ragged rule, or swept with a stiff broom.

The finishing coat, or "fining," should be put on before the first coat has thoroughly set. The two coats will adhere much better when the first coat is quite dry.

The fining or finishing coat is about \ inch thick, and is put on and brought to a uniform surface with a short traversing rule or float, and finished with a hand float. Inferior work is laid on and finished with a hand float.

Should the work dry too quickly, water must be splashed on with a brush and the surface hand floated until the glossy appearance has totally disappeared.

The work is then finished by being lined out to imitate blocks of stone. Lines are ruled with a jointer on the face, 1/8 inch wide and 1/8 inch deep before the fining is set, - this is called "ironing in," and makes a good clean and weather-proof joint.

The usual proportions of the rendering coat are-

1 Portland cement. 3 or 4 parts sand.

And the fining coat -

1 Portland cement. 1 to 2 parts sand.

Cornices and Mouldings are run as follows: - The rule is fixed at the top for the "nib" and one at the bottom for the "slipper" of the "horse" to run against, the brickwork having been previously profiled to the rough shape of the cornice or moulding. The material is laid on gradually, and the horse is frequently run along the rules and the moulding thus brought into shape. It is then finished with hand floats of different sizes and shapes on a joint rule. As the fining coat is difficult to keep on the floats, it is a great temptation to kill the stuff (i.e. by allowing it to set and knocking it up again) in order to make it work easier. This should never be allowed, as it is very detrimental to the strength of the work when finished.

The Following Are Useful Tables In Connection With Plastering

One yard rendering requires -

1/3 cubic foot lime.

2 1/2 ozs. hair.

1/2 cubic foot sand.

1 3/4 gallon water.

One yard render and set requires -

1/2 cubic foot lime.

3 ozs. hair.

1/2 cubic foot sand.

2 gallons water.

One yard two coats and set requires -

3/8 cubic foot lime.

3 ozs. hair.

2/3 cubic foot sand.

2 1/2 gallons water.

One yard render and float requires -

1/2 cubic foot lime.

2 1/2 ozs. hair.

3/4 cubic foot sand.

2 1/2 gallons water.

One yard render, float and set requires -

3/5 cubic foot lime.

3 1/2 ozs. hair.

3/4 cubic foot sand.

2 3/4 gallons water.

2 bushels grey stone lime equals

1 bag

3 bushels blue lias lime equals .

1 bag

2 bushels Portland cement equals

1 bag

14 lbs. plaster of Paris equals

1 bag

1 lb. of hair is allowed to 2 cubic feet of coarse stuff for good work, and to 3 cubic feet for common work.

1 1/2 cubic foot lime will once lime wash over 100 yards super.

2 cubic feet lime will twice lime wash over 100 yards super.