If the apartment be a principal passage, its breadth may be one-third of the breadth of the principal room ; and if it be a by-passage, or that of a very common house, its breadth may be one-fourth of the breadth of the principal room : the height is the height of a story ; but the length is inde finite.
With respect to the staircase apartment, the area occupied by the floor depends on the height of the story, the rise and tread of the 'steps, the formation of the plan, the number of quarter or half paces, and the size of the passage, or lobby, at the beginning or landing; also whether the stair be made single or double ; or whether it consist of one or two revo lutions in the height of the story. The proportion of the dimensions of the plan of the staircase depends on the pro portion of the individual dimensions of each apartment, the proportion of the area of the plans to one another, and their disposition. A principal staircase should never consist of two revolutions. The more of an oblong the plan of a staircase is, the less room will be required, provided the going of the steps be placed in the breadth, and that each flight on the opposite side consist of an equal number of steps, connected by windows, between the flights ; since by such means the lobby and landing above are shortened, and also less room is occupied by the newal. What further relates to staircases, will be seen under the article STAIRS.
To preserve the best possible proportions in a floor of apartments, the principal rooms may have flat ceilings ; the middle-sized ones may have their altitudes reduced by intro ducing cove and flat ceilings, cylindrical vaults, domes, groins, &c., as may be most suitable to their heights ; and the smallest rooms may have mezzanines over them, wherever they are accessible to back stairs; but when the disparity is great between the height of the principal rooms, and those of the middle size, the whole of the rooms in the suite, except the principal ones, may have mezzanines above ; the middle-sized rooms may have flat ceilings ; and the smaller rooms arched ceilings. Mezzanine apartments are not only necessary on this account, but they may be employed with great advantage, since they afford servants' lodgings, baths, wardrobes, &c.
In buildings where beauty and magnificence are preferred to economy, the halls and galleries may be raised to the height of two stories. Saloons are most frequently raised the whole height of the building, and have galleries at the height of the stories, around their interior circumference, communi cating with the various apartments. In general the area occupied by the saloon, may be half of that occupied by the dining-room, drawing-room, or principal-room.
The walls of apartments may be ornamented with columns, pilasters, entablatures, niches, recesses, panels, &e., as also with foliated and other enrichments.
When an apartment is adorned with an entire order, the entablature may occupy from one-sixth to one-seventh part of the height of the order, or of the room itself, when the ceiling is flat. If a cornice, frieze, and astragal are executed, instead of the full entablature, their height may be equal to one-tenth. If a cornice only is executed, its height may be one-twentieth or one-thirtieth part of the height of the room. In general, all interior proportions and decorations should be smaller and more delicate than those of the exterior : pilas ters should not project more than one-eighth, or one-tenth of their breadth ; and architraves round apertures should, in most cases, not exceed one-seventh of the openings. When the sides of rooms are straight, and are adorned with columns or pilasters ranged the whole length of each side, the columns or pilasters may be either single or coupled, as the piers of the windows may admit : if each extreme pier be equal to, or more than the half of each intermediate pier, the columns or pilasters may be placed single, or in couples, as the breadth of the intermediate piers may allow ; but if each extreme pier, or one only of them. be less than the half of each intermediate pier, it will then be necessary to couple the pilasters. if one of the extreme piers is greater than the other, the former may be made equal by forming the end of cylindrical ; if each extreme pier exceed the breadth of each intermediate pier considerably, then both ends may be formed into cylindrical surfaces, or otherwise columns may be introduced at each end, and the entablature con tinued over the columns; the recesses also may be adorned in a different manner, or one of the ends may be made cylin drical, and the other colonnaded.
Apartments of a quadrangular plan are either constructed so as to have the same symmetry on the opposite sides ; or to have no corresponding symmetry whatever, on either pair of these sides. When bows are introduced into apartments, they are generally at the ends; but if upon one or both sides, they should be proportioned to the length. Sometimes, in very large apartments, with a fireplace at each end, two bows are introduced.
In the best houses, kitchens, halls, servants' rooms, and water-closets, are frequently wainscoted to the height of about four and a half feet, and coped with a neat moulding, which is generally a bead.
Halls, passages, staircases, and bedrooms, have frequently bases without dado, or surbases. Principal rooms have always complete pedestals. Apartments laid with stone pavements, should have stone plinths, with wooden bases.
All further information respecting the finishing of apart ments, will be found under the heads, CEILINGS, COMPART MENT CEILINGS, VAULTS, DOORS, WINDOWS; and other par ticulars relating to distribution will be found in the article DESIGNING.