Requirements, Considered Aspects

Walls as room delimiters

Rooms must be completely enclosed by walls or roof surfaces. All wall openings (doors, windows, breakthroughs) also delimit a room. In the roof surface, chimney and window openings are considered closed for the room.

If a room should not be divided into two rooms by a wall with a large breakthrough, it is not sufficient to enter a large breakthrough as a 'door opening'. In this case two wall stubs with a gap between them must be used.

If rooms are to be determined that are not fully enclosed by 'natural' walls, walls with the designation 'room delimitation only' must be used. These walls automatically have a thickness of 0.0 and do not affect measured quantities such as wall areas, etc. They only delimit the room.

• They are used to separate a large room into two areas; typical: living, dining.

• Even for actually unenclosed spaces, such as terraces, these walls are used to delimit the rooms. Such rooms are considered both in the Living Space Ordinance and in DIN 277. They correspond, for example, to DIN 277, category b) 'covered, not fully enclosed' and category c) 'not covered'.

If a wall has the option 'facing wall' for room determination, it is not considered a room boundary. If a facing wall (function of the wall) actually delimits the room in an area such as a knee wall, it should be given the standard option 'room delimitation' for 'room determination'. This has no effect on the measured quantities of the wall, only on its consideration in delimiting the room. These situations occur mainly in the roof area, where even a low facing wall created by roof intersection (knee wall) can be room-delimiting. Therefore, a facing wall with a maximum wall height of at least 4.0 m is always considered as 'room delimitation'; here the 'maximum wall height' and not the actual wall height is decisive. For the knee wall, alternatively the maximum wall height could thus be set to over 4.0 m.

When determining rooms, various particularities, e.g. window niches, are analyzed. Therefore it is necessary that the room boundaries are determined automatically in the program using the 'interior point' function; the input of a 'free polygon' is not possible.

If rooms must be delimited differently than prescribed by the natural walls, walls with the designation 'room delimitation only' must be used.

Lower edge of the room, room bounded below by ceiling panels

To determine the room polygon, a cut is made through the walls and, starting from the click point, a closed polygon is searched for. The elevation of this cut corresponds to the uppermost ceiling level at that location:

• Only ceilings in the area of the lower edge of the current storey are considered. Range: storey lower edge -0.6 m to +1.0 m.

• The ceilings do not have to belong to the current storey.

• At this location several ceiling panels can lie on top of each other (e.g. one panel for the raw slab and one for the floor construction). The top side of the uppermost ceiling panel is found.

• Ceiling openings are ignored; the ceiling is therefore considered closed for this procedure.

At the click point there must, however, be a ceiling present according to the described criteria in order to delimit the room downward.

Since the horizontal cut for room delimitation is generated at this location, the click point should lie on the highest lower edge of a room so that the room is fully captured. At this lower edge the cut must be able to intersect all delimiting walls and run into door and floor-to-ceiling window openings.

For room recognition it is therefore not a problem if a room has lower edges at different levels, but this will affect various measured quantities. This can be caused by different floor constructions or deliberate steps.

It should be considered, if necessary, that a roof surface delimiting the room may also be cut at this level.

Initially, different lower edges within a room are not considered for the results:

• If the different levels arise from different floor constructions, this technically does not matter for the results because the height differences are minimal.

• The lower lying room area is not taken into account in the measured quantities. This particularly affects room volumes, 1- and 2-meter lines and proportional wall areas.

• The floor areas of these rooms are basically determined correctly. Only the shares below 1.0 m or 2.0 m may be larger than necessary, i.e. they err on the safe side. Practically this is also not significant, since rooms with real steps, e.g. lowered living area in the living/dining room, usually have clear heights of more than 2.0 m anyway.

If unacceptable differences result in a lower-lying room area, the lower-lying area should be separated with a wall (room delimitation only) and recorded as its own room.

Room delimitation above

The room must in principle be completely bounded above by ceilings or roof surfaces. All ceiling openings are considered closed. In roof surfaces, chimney and window openings are considered closed; the room runs through openings from dormers or roof intersections.

An exception is a room that, according to DIN 277, belongs to category 'c) not covered'. This room is by definition not covered or not completely covered by ceilings or roof surfaces. For the determination of the room volume (Net Room Content, NRI) according to DIN 277, the height of the lowest enclosing wall is used here.

The underside of the roof surface is considered the lowest layer. It is not analyzed whether roof components (e.g. rafters) project beyond this layer. Thus, the consideration of visible rafters can be controlled via the thickness of the layers: If these should not delimit the room, the lowest layer ends at the top side of the rafters. If the room should be determined only down to the underside of the rafters, the thickness of the layers shifts the lowest layer to the underside of the rafters.

This has an effect particularly on the determination of room volumes and the level lines (1-, 2-meter lines of the Living Space Ordinance).

Ceiling openings, galleries

In the area of ceiling openings the rooms are considered bounded downwards and upwards. Ceiling openings are therefore always treated in accordance with the standards as openings for installations or as stair openings with a small stairwell; the stair thus largely fills the ceiling opening.

We refer to a gallery when the upper room ends at the boundary of the ceiling and does not extend to the corresponding wall; the lower room at this location passes the ceiling upward to the next ceiling or roof surface. To create such a gallery, the outline of the ceiling panel (reference polygon) is entered according to the gallery.

Consideration of door openings, door niches

Door openings are considered closed for room delimitation; a room therefore cannot run through a door, even if it is a large breakthrough.

For hinged doors the door leaf is on the opening side, for sliding doors in the middle of the wall. For breakthroughs the floor separation is also in the middle of the wall.

Door niches are not considered in the Living Space Ordinance and DIN 277. However, they are considered in the 'room geometry - floor area'. Further details are provided in the description of the measured quantities below.

Consideration of window openings, window niches

Window openings are considered closed for room delimitation; a room therefore cannot run through a window.

Windows are relevant for room determination only when they are floor-to-ceiling, i.e. when the lower edge of the room (top of the floor) extends into the window niche. In the following we therefore speak of window niches only for floor-to-ceiling windows. For room delimitation the window is currently always positioned in the middle of the wall.

Window niches are not considered in DIN 277. They are, however, considered in the Living Space Ordinance and the 'true floor area'. Further details are provided in the description of the measured quantities below.

Consideration of chimneys

Chimneys are generally subtracted from rooms. However, not the respective roof or ceiling opening with closure is used for this, but the cut through the actual chimney. To ensure that the resulting opening is actually subtracted, it is compared with the minimum deduction sizes.

Consideration of internal walls

If a wall projects into a room, it is always subtracted from the floor area and room volumes if it has the option 'room delimitation' for the parameter 'room determination'. The wall surfaces are included on both sides in the result.

Multiple room-delimiting walls can form an island within a room if they do not touch walls of the outer room boundary. Such an island is detected and always subtracted from the floor areas and room volumes. The room-side wall surfaces are included in the results.

Facing walls are generally not used to delimit rooms. (except if they have a maximum wall height of at least 4 m.) Depending on the regulation, they must be taken into account or subtracted in the determination of room sizes depending on their size. Further details are provided in the description of the measured quantities below.

Consideration of wall niches

In some regulations (Living Space Ordinance) there are references to floor-to-ceiling wall niches. A wall niche is understood to be a recess in a continuous wall. A bay formed by the course of several walls is therefore not a wall niche.

True floor-to-ceiling wall niches are rare and cannot be entered directly in the system; accordingly they are also not considered in room determination.

Consideration of staircases

Staircases are initially considered only indirectly via ceiling openings (here floor openings); ceiling openings are treated as 'stair openings' as described above. According to the Living Space Ordinance the stair opening is subtracted from the living area; only where the stair begins, i.e. where there is no further floor opening, is the floor area beneath the stair taken into account. According to DIN 277 the stair openings are not subtracted from the room there.

However, for the Living Space Ordinance and DIN 277 there is no subdivision of the area below the stair according to the clear height.