Affordable Low and High-Rise Honeycomb Housing - 5 new articles
THE PROBLEM OF CAR PARKS FOR HIGH RISE
Malaysia is reputed to have one of the highest levels of car ownership in the world. The planning requirement for apartments is two units of car parks for each unit, plus another 10% for visitors. This is a very high requirement compared to most other countries and has the effect of making our high-rise housing expensive.
MEETING HIGH CAR-PARKING REQUIREMENTS WITH THE CHECKERBOARD PLAN
As we design taller buildings to achieve higher densities, just adding on parks on the ground is not the way to do it. The additional area required to cater for the additional car parks increase the development land required: since density is units/land area, increasing the numerator is pointless if at the same time, we increase the denominator.
To achieve higher densities, multi-level car parks are necessary. They can be placed in an adjacent block or below the tower. Constructing an adjacent block is cheaper but at the cost of being requiring an additional area, hence resulting in a lower density. But whichever of the two, the effect on the distribution of built-up area is that a large built-up area is now dedicated for cars: the net sellable area becomes a smaller proportion of the total built-up area. Car parks takes up a lot of space. Each car needs an 8’ x 16’ space that works out to 128sf. The driveway takes up 20’. All in all, with ramps and having to consider building columns and staircases, the gross built-up area required for one car park is about 260sf: in fact, actual car parks make up less than half of the total area of a multilevel car park block. Two car parks for each apartment plus another 10% for visitors takes up 572sf of car park built-up area. This is more than half the size of a typical affordable apartment.
Net sellable floor area expressed as a percentage of total built-up area for high-rise, including the multi-level car park plummets is often less than 55%. The fact is, the car parking requirement for high-rise high-density housing has become a very heavy burden on the cost of construction.
Again, PR1MA is aware of this problem and have produced their own guidelines which try to address this problem. In their table, A1, the car park provision for rural areas is set at 2.2, suburban and urban areas at 1.65 and 1.1 in cities. Although this standard may face resistance from local authorities and householders used to the convenience of having two cars, in the longer term, promoting a less car-dependant life style makes sense.
Already, the average size of households in Malaysia has peaked , bringing down the average number of cars per household. With the expansion of public transport in Kuala Lumpur and the Klang Valley, plus the explosive growth in share-riding services like Uber and Grab, owning a car is not essential for young working people, as it once was. I believe that PR1MA can do a good job in convincing local authorities home-buyers to buy into the concept of the compact city that promotes high residential density, mixed use and is oriented towards pedestrians rather than cars.
The efficiency of car parks can be operationally improved by doing away with parking spaces that are strictly allotted. As currently practiced, car parking spaces are allotted as accessory parcels to each owner. However, this ends up with a lot of car parks being empty for long periods. A pooled system, as found in commercial buildings, can cut this slack, providing more car parking opportunities with fewer actual slots.
In fact, PR1MA’s guidelines presumes only two basic options – a stand-alone multi-level car park or a podium car park that sits below the building block.
Figure 15 Multi-level Podium Car Park
The latter is of course more efficient than the former. But the podium is still a poor choice. The podium takes up space larger than footprint of the tower or slab block above it. This increases the land area that is needed. The car park podium also must be set back from the boundary by about 50’ from the front and 25’ from the side. Having to do so results in having fewer cars than car parks on the ground floor which are subject to much lower setback lines.
Is there a better solution?
DEEP PLANS: PROVIDING CAR PARKS MORE EFFICIENTLY
The checkerboard-plan was conceived to be car park design-friendly with columns spaced in an 8m grid. A car park circulation system also fits neatly into the 5-layered grid with two roads inside the building footprint feeding car parks on both sides.
Figure 16 Columns in 8.1m grid
There is a road that circles the outside of the building: it too feeds car parks on both sides. The ground floor plan is shown below.
Figure 17 Ground Floor Car Park Plan
On just one floor the design is already very efficiently with up to a density 136 units per acre and this one floor is good enough to support a residential density of 60 units per acre when the car park requirement is 2.2 car parks per apartment, 90 units per acre when the car park requirement is 1.65 car parks per apartment unit, and 120 units per acre when the car park requirement is 2.2 car parking spaces per apartment.
But can we provide for even higher densities? Is there an alternative to the conventional multi-level podium car park?
Our answer is to replicate the ground floor car parking layout in a basement floor. In fact, basement car parks are generally not considered at all for residential development because they are thought to be costly to build, needing temporary shoring and permanent waterproofed retaining walls, and costly to maintain, with a mechanical system to draw in fresh air and expel fumes as well as a smoke-spill system in case of fire.
Yet, a single basement level 7’ or more away from the boundary does not need temporary shoring or an expensive water-proofed retaining wall. An 8’ rubble retaining wall at the boundary plus a low 1’ concrete one on the car park building line will suffice, creating an air-well that provides natural ventilation, daylighting, a green planting strip and setback distance to meet current planning requirements.
Figure 18 Perimeter Retaining Wall and Air-well
It is also easy to design an access to a single basement floor, doing away with having too many ramps as shown in the plan below.
Figure 19 Basement Car Park Plan
As shown in the basement car park plan above, just two car park levels can already support a building above it that contains 133 units per acre when the standard is 2.2 car parks per acre, 170 units per acre when the standard is 1.65 car parks per acre, and 275 units per acre when the standard is 1.1 car parks per acre.
The options available are displayed in the drawings below.
A design strategy that achieves high-density with shorter buildings and which either eliminates the car-park podium or else substitutes it with a low-cost single basement floor will surely reduce construction cost and time. Combining it with a lower car parking standard and as well as a loosening of the cap on density will further multiply the savings.
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Even if authorities allow higher densities, high-rise would still be expensive. Taller buildings cost more to build compared to lower ones. As we go higher, there are thresholds above which costs become disproportionately more onerous.
Structures cost more the higher we go, as the columns on the lower floors need to be stronger and as lateral forces become more critical.
Below five storeys, lifts are not considered to be necessary, but at five storeys or above, we must provide them. As we go higher, more lifts are required, not only increasing the cost of installing and maintaining them, but also taking up more space, and thus reducing net sellable area. Lifts above 20, 30 and 50 stories also get disproportionately expensive as they need to move faster and must carry longer and heavier cable ropes.
With respect to fire-safety, above seven stories (top most floor 18.3m above fire appliance access level), fire-fighting lifts and “dry-risers” to pipe up water and hose-reels are required. Above 10 storeys (30.5m fire appliance access level), a wet riser, associated storage tanks and hose reels are required.
As for construction, taller buildings take longer to build because there are more floor cycles to work through, because materials must be transported higher. Blocks lower than 10 stories do not even need a tower crane. In short, shorter buildings are cheaper. But can we design them to a high density?
DEEP PLANS: MAXIMIZING SITE COVERAGE
Current high-rise typologies are narrow buildings: the slab block with a single-loading corridor can be described as a single-layer of apartments; the slab block with a double loading corridor is a double-layer arrangement; the tower block, a circular layer of apartments.
In housing, we want almost every room to have natural light and ventilation. There cannot be deep plans like that found for offices, where mechanical and electrical systems bring in artificial ventilation and lighting to the central portion of the building which are far away or cut off from the windows and the building’s edge.
The typical Malaysian apartment will have at least the living room and master bedroom having windows on the external walls of the building and less important rooms facing an air well. The depth of the unit measured from the external wall is about 8 metres. With a 2m corridor in the middle, the total width of this double-loading corridor block layout, with two layers of apartments, is not much more than 16m.
The width of the single loading corridor with only a single layer of apartments, is about half of this. The tower block, with a circular layer of apartments, can be wider; each side is typically 24m.
In contrast to these existing typologies, the Honeycomb checkerboard-plan has a depth of over 40 metres. This deep plan results in a residential floor plan that covers more of the land available on as site compared to that achieved by skinny conventional floor plans. Using the available land more efficiently allows more units to be built on every floor and so can provide higher densities without having to go taller; it should become easier to achieve high plot ratios like deep plan offices.
Figure 14Apartment Typologies and Minimum Land Required
For a comparison, we take the different floor plans, apply 60’ front setback and 25’side and rear setbacks to form the minimum site boundaries for each example. We measure the area and divide it by the number of apartment units on a typical floor to show how big an area is needed to accommodate one apartment unit. The checkerboard-plan is the most efficient as it takes up the least amount of land compared with the other examples.
Table 1 Comparison of Site Coverage: Per floor Density
The medium-rise Honeycomb apartment with the checkerboard-plan can provide an answer to the problem of affordable housing in the main urban centres of Malaysia. Let me first introduce the concept.
The basic checkerboard layout plan consists of eight duplex units arranged along a 3-storey high sky-court.
Figure 1 A sky-court neighbourhood of 8 units
On each floor are four of these sky-courts that are linked by a lift lobby.
Figure 2 Four sky-courts on one floor in one block
This is the view of the 3-storey sky-court. In this “Honeycomb Apartment” concept, every resident can step out of her main door to her front yard and beyond that, a landscaped courtyard – or “sky-court” with a garden fence off the edge.
Figure 3 View of 3-storey Courtyard
The doors lining the courtyard on the right are the front doors to the apartments. All apartments in this “neighbourhood in the sky” will have such doors, leading into a lofty three storey high sky-court which contains private and shared gardens.
This is a look at the floor plans of a pair of apartments. As per the Honeycomb apartment arrangement, units on the courtyard garden level either have stairs going down to bedrooms on the floor below, or have stairs going up to bedrooms on the floor above. The typical apartment is a duplex unit with living room, dining and kitchen on the courtyard level and three bedrooms, two bathrooms, a utility space and a dry yard on the upper level or the level below.
Figure 4 One level above, Courtyard level, and one level below
Residents here enjoy the benefits of a Honeycomb neighbourhood. They share a communal courtyard with small number of other households, making it easy for neighbours to get to know and interact each other. There is sufficient space and light to garden just outside their home.
With many “eyes” overlooking the sky-court along with safety measures such as a garden fence at the edge of the sky-court and child barriers at strategic locations, the sky-court can be made safe for children. Children can play just outside in the courtyard, making this apartment more suitable for families.
The typical floor plans of medium-rise Honeycomb apartments are shown below:
Figure 5 Podium Level and Podium Level + 1
Figure 6 Floor below Cortyard level, Courtyard Level, and floor above Courtyard Level
Figure 7 The Honeycomb 3-storey Courtyard Arrangement
Figure 8 Another view of the Couutyard
Eight apartments front the typical courtyard, about 8 x 16 metres on plan and 9 metres high. They each have a front-yard 4m wide and 2.4m deep where residents can tend their own garden. It also provides a buffer between bypassing residents and the front door, providing a measure of privacy to the living room and still allowing people inside a view of the sky-court.
By securing the edge with an anti-climb fence and securing access to the lift lobby and escape staircases, the courtyard is suitable for smaller children to play with their parents and neighbours looking on.
Figure 9 Entrance View
At the ground level, the entrance is connected to the public street by stairs that go up a sloped garden that screens the car park behind it. Off the entrance are two courtyards opposite each other which have shops; they each lead to the two wings of the apartment block. In the middle is a community centre with Surau, multi-purpose hall and kindergarten.
Figure 10 View of Entrance Court
The high density of 130 units per acre is achieved by the 12-storey version of the checkerboard plan which has a basement car park where the parking standard is 2.2 car parks per apartment, or with just the ground floor car park where the requirement is 1.1 car park per apartment.
Figure 11 View of 12 Storey Version
Figure 12 Another View of 12-storey version
Unlike conventional high-rise apartments which have similar densities, here the housing blocks are not divorced from the street level, separated by multiple levels of car parks. The ground floor car park can be easily screened-off from the front by a garden that slopes up to the first floor and from the sides and rear by walls and rows of trees.
The bulky mass of blocks is also easily broken up by the sky-courts and façade treatment which introduce strong vertical elements that counter the horizontality of the floors. Adopting duplex floor plans also avoids the monotonous repetition of window patterns on the elevation.
The checkerboard-plan is just another variation of X-plan Honeycomb apartment layout that was introduced in Chapter 11. In this version, the sky-courts are three storeys rather than six. The cost saving features of the X-plan have been retained:
However, to solve the real-world problem of providing housing in Malaysia’s major urban centres, more cuts need to be made.
How the checkerboard-plan can make high densities acceptable, maximize site coverage to fit in more units on medium-rise buildings and provide sufficient car parks efficiently will be discussed in the next post.
When we look at major urban centres like Kuala Lumpur, Penang and Johor Bahru the problem of affordable housing appears daunting. The high price of land requires that very high-density apartments high-rise, but there is a cap on how many houses may be built on each acre of land. Even if allowed a higher cap, high-rise buildings are expensive to build. Not only the apartments, but also the multi-level car parking blocks that must be built.
Here, we look at a high-density apartment design that tries to overcome three hurdles that beset affordability in the main urban centres of Malaysia: how to reduce the high cost of land, the higher costs of constructing tall buildings and the cost of building car parks.
REDUCING LAND COST BY BUILDING MORE UNITS ON EACH ACRE
One way to reduce the cost of land is to have more units share this cost. But the intensity of housing development in Malaysia is controlled by restrictions on the number of housing units that can be built on each acre. At present, most local authorities still only allow high-rise housing up to a density of 60 units per acre, but official thinking about it is changing.
Why do Authorities want to impose density restrictions? The answer must be that people are worried about the negative effects of overcrowding. However, we have already made the point that as we build taller Honeycomb apartments, we also add more green, social spaces that be used for gardening, social interaction and children’s outdoor play.
If indeed, providing each home a private and a shared garden can overcome the social defects of high-rise housing, then why not allow even higher densities, especially if it is to make living in the city more affordable? Very high-density housing is already a fact, albeit under the alternative name of serviced apartments. However, serviced apartments that have been mainly built on prime commercial land have generally been too small and expensive, geared towards investors rather than home-makers.
The Draft National Guidelines on Planning (2013) proposes maximum densities of 60 units per acre for areas under District Councils, 80 units per acre for areas under City Halls or Town Councils and 90 units per acre for Transit Oriented Development within those areas.
PR1MA, a government company tasked with building affordable housing, especially for urban dwellers, has come up with guideline that allow for much higher densities than is normally approved. This is a snip from their guidelines:
According to this, the allowable development intensity for areas under District Councils is upped to 80 units per acre in a rural area and 80-120 units per acre in suburban area, for areas under Town Councils, 120-150 units per acre, and for City Councils, 150 units per acre.
Given how various government bodies are rethinking the issue of development intensity, it makes sense to make the case for allowing higher densities as a strategy to make housing affordable. Doubling the density of a housing development effectively halves the cost of land for each unit. Not only is that a significant amount for urban land, there are also additional savings in the cost of providing infrastructural services for each unit.
The range of high-density options that will be explored below will include all the higher densities that PR1MA has asked for, as well as a prototype for around 200 units per acre.
The ground level is slightly lowered to make it into a lower-ground floor ground floor and is fully utilized to provide car parking. If laid out efficiently, the number of car parks provided will be able to support up to 60 units of apartments per acre. The upper-ground floor is slightly elevated and is connected to the main street with a ramp.
On the upper-ground floor are single-storey apartments arranged around double storey courtyards. Surau, Dewan and some shops can also be provided on this floor. Two floors above this, on the second floor are another set of courtyards which are partially open to the sky. Here, the courtyards provide access to duplex apartment units in the typical high-rise Honeycomb layout.
The Honeycomb layout proposed provides a private front-yard to each unit well as a communal garden shared by groups of 8 duplex apartments on the 2ndfloor and 4 single-storey apartment units on the upper-ground floor. The typical size of the duplex front-yard is 8sm. The landscaped communal courtyard area that serve 8 duplex apartments are 4m x 12m. On the upper ground the typical front-yard is 12sm and the communal courtyard is 5m x 8m.
The apartments are like terrace houses where residents have a front garden facing a car-free “street” in the air where children can play. In trying to convince purchasers who prefer conventional landed property which are too expensive, playing on this imagery can help make apartment living more desirable.
The efficient use of the lower ground floor makes it possible to design up to 60 units on each acre of development land using only a 5-storey building type. In this way, the benefit of high-density is achieved without recourse to going above 5-stories and having multi-storey car parks with all the extra costs that these features entail. This results in a lower cost structure that combines both low construction and land cost.
We can further add value to the cost-efficient 5-storey walk-up flat by providing lifts and adopting the Honeycomb layout. They wouldn’t be too expensive: they serve only five floors and unlike lifts that serve taller buildings, need not be fire-rated; downtime for maintenance is acceptable without having a second back-up lift next to it. In the 5-storey Honeycomb Apartment Layout, the lifts need only stop on the lower-ground floor (car park), upper-ground floor and 2ndfloor only.
There is a mix of duplex and single-storey apartments of differing sizes in this layout. It was designed specifically to meet the low-cost, low-medium cost and affordable categories of housing that is mandatory in the State of Johor with smaller single storey units in less desirable locations assigned as low-cost and low-medium cost houses. In this way, the building of separate buildings for each housing category is unnecessary. Shops are also provided to make this mixed income community even more conducive to the development of a healthy community.
This high-density low-rise apartment block is different from conventional slab blocks in that it is much wider. This partially explains how sufficient units can be provided on each floor to achieve 60 units per acre. The other important reason for it is the efficient layout of car parks on the ground floor to achieve the sufficient number of car parks.
This design would be suitable for infill sites in most suburbs where there are already terrace houses built or going to be built, but which have become too expensive for most people.