Corridor accessed residential building

5.8.1. Open corridor apartments

Open corridors in some situations are enclosed with glazing.

In some situations, when supported on consoles, these corridors are referred to as suspended corridors.

Open corridors are usually used to allow for ventilation and better daytime sunlight to apartments.

These corridors are usually protected from rain by the corridor of the floor above – except for the top floor, which is usually sheltered by the roof’s projecting eaves. (Experience has shown, residents of top-floor apartments sooner or later cover the corridor themselves with lightweight, makeshift roofs).

Some people do not like these open corridors, because they can induce feelings of vertigo; hence, measures are taken to enclose the balustrade. (fig. 5.36)

Figure 5.33. Design of side access corridors

When considering rooms adjacent to the corridor, recognize the fact that passers-by can see in. A higher parapet window might be used where tolerable (bathrooms or kitchens). However, living rooms and bedrooms placed in this location are very uncomfortable, requiring translucent curtains. Residents wishing to prevent a loss of privacy or malicious intrusion may not be able to open these windows.

In some situations, an open corridor may be pulled away from the elevation as an independent structure, allowing access to homes by short "bridges". Although this is an interesting solution to the problem, it would be better to plan apartments with non-habitable rooms adjacent to corridor.

Rarely are these open corridors enclosed. In such instances, where a kitchen is not part of an open-plan apartment, mechanical ventilation must be provided. Consider glazing for the corridor, especially if it is on an exposed north side, since this might be of help regarding energy efficiency issues. This

"buffer zone" can be beneficial, but might reduce the effectiveness of natural ventilation. It is also prohibited to use enclosed corridors for ventilation of apartments; therefore, alternative ventilation must be provided.

Correct orientation of open corridor buildings is relatively problem-free. Buildings placed on a north-south access are ideal, as both sides will receive light in the daytime, so one is free to choose which side will house the corridor. When a building is placed on an east-west axis, ensure that the corridor does not run along habitable rooms. When a building faces north on the street side, then place the open corridor on the northern elevation. Open corridors facing the street can often look bizarre, so take care to detail the building appropriately with this in mind.

Even in buildings with only a few floors, it is advisable to include a lift. The cost in proportion to the overall development is not significantly increased, but the amount of apartments served is often relatively high. It is also recommended to use a larger, eight-person elevator to allow for wheelchair and pushchair access, even when a smaller lift might be suited in terms of actual resident capacity.

Remember that this should also offer barrier-free access to all floors and corridors.

The narrowest unobstructed width for this corridor type should be 1.10 m, although 1.20 m is more recommended. In buildings deemed to be barrier-free, a width of 1.50 m is better, since this allows for easy access to the lift and turning space for wheelchairs. The furthest distance to an apartment’s entrance door must not exceed 30 m from the stairs. Even now, this is considered the extreme limit in terms of calculating the "evacuation time". Evacuation time is not calculated at each level; it is based upon the time needed to evacuate the building in case of fire. Therefore, corridor length and width might vary from floor to floor according to the number of people served and the build ratio at different heights.

The stairwell should be placed where there is the greatest concentration of use. The stairwell is usually placed on the outside of the corridor, but often located between two apartments. (fig. 5.37) In mid-rise buildings, the stairwell should be smoke free. In many mid-rise buildings, a second escape staircase is provided to reduce evacuation times. In high-rise buildings, the second staircase is mandatory, and one of the stairs must be smoke free.

Figure 5.34. Examples of vertical circulation cores in side access corridor residential buildings

5.8.2. Closed corridor apartments

Closed corridors are those found within the building’s interior. Some buildings might have a dual system of closed corridors (parallel corridors to separate residential and non-residential users,

accessing the central core from different directions in linear developments). These corridors are placed along the building's axis and are also referred to as an "aisle".

Both sides of a closed corridor provide access to apartments; therefore, it is ideal for the building to be placed along a north-south axis, or as close to it as possible.

An enclosed corridor needs ventilation at both ends, from windows or from hallways connected at the sides. Mechanical ventilation can be provided when natural ventilation is not achievable. Fire regulations might call for mandatory high-power smoke extraction systems. Mechanical ventilation consumes energy with high operating costs. Long corridors require artificial lighting, even during the day, increasing energy use. It is preferable to design for natural daylight and ventilation.

Corridor length and width should be calculated in terms of evacuation times. Unless otherwise stated, corridors should be a minimum width of 1.50 m, although 1.80 m is more recommended. (Narrow corridors can seem claustrophobic.) Doors to apartments must open in to prevent the obstruction of escape routes. (Doors in corridors must open in the direction of evacuation where the number of potential evacuees exceeds 50 people. Individual apartments do not require an escape route for 50 people.)

5.8.3. Correlation between rooms provided and floor areas

Due to the size of corridors and circulation routes, it makes economic sense to provide the maximum number of apartments possible over the building’s entire planned area. Figure 5.39 illustrates different plan types in relation to corridors and their respective economic impact. The sizes given are based on average apartment width, rarely exceeding 4.50-5.00 meters. These apartments are well suited to open corridor buildings, since their floor areas (30-40 m²) are relatively small, providing a depth of 7.00-8.00 meters. Nonetheless, smaller building depths have proportionally larger elevation areas (hence, higher heating and construction costs). Single-room apartments can have internal kitchens with windows facing the corridor. This might require additional corridor space within the home. Where a building depth is 14-18 m, smaller unit homes are still favorable when used in conjunction with a closed corridor. If a building developer requests a building with one-room dwellings (studio apartments), it makes economic sense to provide access to them via a closed central corridor.

Figure 5.35. Various apartment schematics for corridor accessed homes

From an occupant’s point of view, closed corridors are less preferable than open corridors. From an economical standpoint, an open corridor building might cost more to build than a closed corridor building and have increased real estate potential. Marketing of properties is not always related to the economics of construction. In this example, cost of construction is being compared.

Living room plus one bedroom (or two-bedroom) homes are favorable when apartment width is between 7.00-8.00 meters. The kitchen can be lit naturally from an open corridor. These apartments are

best suited to open corridor developments when the depth is within the range of 8.00-9.00 meters. This size of residence also works in closed corridor homes if the developer does not demand natural light and ventilation for kitchens. When this type of home is planned with apartments that are 9.00-10.00 meters wide, the size of corridors comes under question. (A 30-meter-long corridor can only support six apartments.)

Placing two-bedroom apartments (even three-bedroom) can be critical if traditional corridor arrangements are required. Open corridor buildings in this situation are best provided one bedroom opens onto a corridor. If not, three bedrooms will need to be placed along the elevation, which could become 10.00-12.00 meters in width. This will require all ancillary rooms to be placed on the corridor side of the apartment or absurdly shallow building depths.

Conventional corridor arrangements are best suited to smaller apartments – this being for guideline purposes only. In some cases, a relatively short open corridor might have larger apartments placed at each end, in which case bedrooms overlook the corridor side of the building. Similar corridor arrangements are also used in hotels or guest apartment buildings, but these fall into a different economic class. (Single entrance is required due to continuous porter service.)

Where narrow apartment widths are developed, two-storey (duplex) homes are often planned. The access corridor is placed at alternate levels. The interior arrangement of these apartments is usually referred to as "maisonette". (fig. 5.40) No doubt, the individual cost of construction per residence is greater (including interior stairs), but this can be offset by the fact that half as many access corridors need to be built. Maisonettes can not be developed as barrier-free homes on both floors.

Figure 5.36. Double storey homes in side access corridor buildings

It is also common for two-floor loft apartments to be built on the uppermost level of open corridor buildings.

5.8.4. Complex planning arrangements

Larger homes have many varied approaches to the design of access corridors (sometimes very complex), often seen in Western European developments in the 60s and 70s. This obviously has an ideological basis, based upon a preference for higher buildings.

A beautiful example of two-story homes being arranged around a closed corridor was developed by Le Corbusier in the "Unié d'Habitation". (fig. 5.41a)

The corridor provides access to the home at a split level (shown in figure 5.41b), creating what was termed a "semi-duplex" (shown in three dimensions in figure 5.41c).

Figure 5.37. Spatial arrangement of corridor access (examples)

Despite the interesting architectural spatial arrangement of interior spaces in these "semi-duplex"

homes, barrier-free access is not possible, and residents do not enjoy the continuous need to use the stairs.

Originally, the building was developed with the intention of creating complex spatial arrangements that are either seldom used today or thought more applicable to lower-rise buildings. These brave feats of engineering and often complex spatial layouts are not possible now, even in lower-level buildings.