The size of rooms depends in each individual case on the purpose they serve and on the function of the building as a whole. In a dwelling the human being is the principal scale for determining all dimensions used, while comfort and hygiene play an especially important role here, and even the most modest building must meet their basic requirements.
According to sanitary standards, optimally comfortable conditions are provided if each person has no less than 30 sq. m, but taking the psychological factor into account a person needs 40-50 sq. meters.
When determining the size of a living room, the main attention should be given to the volume of air it contains, as required for the occupancy of a given number of inhabitants — adults and children, as well as to convenient placement of the necessary amount of furniture, while still leaving sufficient space for people's everyday activity.
Room depth. Of the three dimensions that determine the size of a room, i.e. length, width and height, particular importance belongs to the dimension perpendicular to the exterior wall of the room, i.e. its depth.
Depth, in the terminology accepted in building practice, is defined as the distance from the exterior wall of the house to the opposite interior wall. Depth will be either the length or the width of the room, depending on whether the other horizontal dimension proves smaller or larger.
Depth is determined by the feasibility of the house's structural scheme (for example, the possible length of a wooden ceiling beam)
In addition, depth affects the possibility of obtaining a sufficient amount of daylight in the room, as well as the convenience and manner of furnishing the room.
Dependence on room lighting. The depth of a room depends on the possibility of lighting it sufficiently and evenly with daylight. To meet this condition it is considered necessary that rays of light falling from the upper edge of the window onto the opposite end of the floor form with the plane of the latter an angle of no less than 30 degrees.
It follows from this that the depth of a well-lit room will always be less than twice the height of the window lintel from the floor, and, consequently, all the more so less than twice the height of the room itself, since the latter is greater than the former.
For sufficient lighting of deep rooms both a larger window area and considerable height are required, ensuring the above-mentioned angle of incidence of light (30 degrees).
Room height. Room height is determined mainly by a person's stature (average height about 1.75 m).
Since in a room enclosed on all sides the air spent by breathing accumulates in large quantity under the ceiling, it is necessary that it be considerably above the head of an adult — at least 0.75 m. Thus the minimum room height will equal 2.5 m.
The higher the room, the more favorable it is, of course, not only in terms of hygiene but also in respect of good daylight. However, the cost of the building itself increases considerably with great room height, and even heating in winter becomes more difficult. Besides, for aesthetic reasons a moderate height is recommended, since rooms that are too low produce an unpleasant, oppressive impression, while those that are too high, on the contrary — lose the attractive character of coziness.
The overall impression produced by a room depends to a considerable degree on a well-chosen height. It is well known that low rooms appear larger than high ones of equal floor area.
As already stated, to obtain a pleasant impression of a room it is necessary that the relations between height (h) on the one hand and length (а) and width (b) — on the other be correctly chosen. The best proportions for this purpose are expressed by the following formulas:
h = 1/3 (а + b),
i.e. the height constitutes one third of the sum of length and width.
From this relationship it is clear that a suitable height of living rooms will always be less than their length, as the greatest of the horizontal dimensions.
The various formulas in use give almost the same result, which is why in general one may say that an appropriate height of a living room will be somewhat greater than half its length or two thirds of its width and less than three quarters of the length or the full width. This is clearly expressed by the general formulas:
h > ½ а or > 2/3 b and h < ¾ а or < b
In rooms with height chosen in this way, part of the wall together with the floor and ceiling is seen by an observer from the opposite end of the room at a normal visual angle (of 30-45 degrees), which produces on the person entering a unified and pleasant impression.
Within the limits established here the actual room height is then chosen depending on the combination of other special conditions affecting its size, such as: the purpose of the room, the degree of its illumination, the required amount of light, and so on.
Overall height of rooms. For the convenience of construction, as well as in view of better communication with the parts of the house above, the height of all rooms on each individual floor is usually made the same, and its dimensions are determined by the size of the most important rooms. In most cases, however, a moderate overall height is assigned. An increase in height entails construction costs.
In those cases when it is required to give greater height to one or several adjoining rooms of the house that differ in size and importance, the following methods are applied:
1. Lowering the floor, if the room is located on the 1st floor or above secondary rooms
2. Raising the ceiling, if the room lies on the top floor or under secondary ones
3. Carrying the room through two full stories, if considerable height is required and if the floor above is suitable for this purpose.
A reduction in height for small and secondary rooms, as well as for setting off certain parts of them, such as bay windows and alcoves, is achieved by methods opposite to those just indicated, namely by lowering the ceiling or raising the floor by one or several steps.
