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
No of
Units /Floor
|
Site
Area (sf)
|
Site
Area /Unit
|
Units
on Floor/Acre
|
|
Woodlands
Drive, Singapore
|
6
|
35,731
|
553.4
|
7.3
|
Single
Loading Corridor
|
||||
Blues
Point Tower , Sydney
|
4
|
22,555
|
524.1
|
7.7
|
Tower
Block
|
||||
Membina
Court, Singapore
|
10
|
50,903
|
473.1
|
8.6
|
Cluster
Block
|
||||
Binapuri
Tower, Selangor
|
8
|
37,554
|
436.3
|
9.3
|
Double
Loading Corridor
|
||||
Honeycomb
|
10.67
|
43,264
|
376.8
|
10.7
|
Checkerboard
-Plan
|
No comments:
Post a Comment