Caravan and Residential Parks and Population Density

So as I have tended to point out here and elsewhere on the net, humans have legs and are meant to be mobile, they are not plants anchored to the earth and trapped in one place. However humans cannot remain permanently in motion, they need to rest, and a place to rest. Whilst the minimum requirement is just access to a place where can lie down and sleep, it is preferable to provide certain amenities to maintain hygiene for society and protect the environment. The current article is primarily about space and circulation, and population density. Thus it packs as many shelters into the available space as possible, providing adequate circulation around such shelters, but ignoring other requirements such as the space required for septic tank drainage.

Circulation is important as lack of circulation is responsible for the two we events which contributed to the development of modern building codes. These events are:

  1. The great plague of London (1665 to 1666)
  2. The great fire of London (1666)

A lack of adequate spacing and circulation prevented access to spaces to remove vermin. A lack of circulation also related to a lack of natural ventilation, and consequently lack of fresh air. A lack of circulation also prevented access by firefighters and also contributed the further spread of fires. Thus primary criteria in building regulations and building codes concern health/amenity, access/egress and fire protection.

The South Australian development act and regulations, require a building is either on the boundary or a minimum of 600 mm away from the boundary.

Personally I don’t agree with the “on the boundary” allowance. I believe a building should only be permitted on the boundary if it has a shared or common wall with the building on the other property. If not then a gap will exist between the two walls, which will be contrary to the intent of the rules. If one owner is allowed to build on the boundary, without a common wall, then the owner of the adjacent property should be required to be 600 mm from the boundary: which likely to be seen as unreasonable. Therefore the boundary wall should be required to be constructed as a shared common wall (with specified fire rating and acoustical properties). The two adjacent properties do not have to build on the boundary, one can still choose to be 600 mm from the boundary, but if the owners do choose to be on the boundary they have to use the common wall. Half the thickness of the wall resides on one side of the property boundary, the other half on the other property boundary. However the full thickness wall always has to be constructed. If considered legally similar to a fence then the owners on one side of the boundary may not wish to contribute to construction of such wall.

The 600 mm clearance, is to provide access to remove pests and vermin and also avoid the accumulation of litter. It is typically measured from the face of the wall to the boundary. I consider this to be faulty, and that it should be measured from the envelope of the building so that have access to the edges of the building, and there is proper clearance between buildings. There should not be a continuous roofscape.

For example if have 600 mm eaves overhang and 150 mm gutter, then to avoid the gutter overhanging the boundary the wall needs to be 750 mm from the boundary. If houses on adjacent properties are similar, then the gutters touch at the boundaries and are only accessible from the roof. It should be possible to clean the gutters from a ladder or preferably mobile scaffolding platform. It is therefore the gutter which needs to be placed 600 mm from the boundary: thus the wall is 750+600=1350mm from the boundary.

The national construction code (NCC), and building code of Australia (BCA) place additional boundary clearances for fire protection. For residential the typical clearance is 900 mm whilst for commercial the clearance is 3000 mm, to avoid walls with a fire resistance level (FRL). These are clearances from the boundary, which is considered to be the source of the fire. Thus source of fire providing protection from is the neighbouring property.

For residential there are complications concerning the location of class 10 buildings relative to the main dwelling, and the boundary, the distance may increase to 1800 mm.

Now the basic requirements of the development regulations and the building code maybe surpassed by local council requirements as set out in their local development plans. For example side clearances of buildings 1000 mm, set back 6000 mm and rear clearance 5000 mm. This taken into consideration with minimum area requirements for open space, parking, and landscaping, with some minimum dimensions given in one or both directions of a rectangular area. There are also minimum block sizes.

The minimum block sizes permitted for land subdivision depends on land usage. As far as I am aware there are no minimum dimensions for a building: though there are certain required facilities and performance criteria for these. Thus the minimum size for a dwelling is set indirectly.

Whilst the quarter acre block (approx: 32m x 32m [1024 sq.m]) was once the common Australian dream, this reduced to sixth of an acre (approx: 21m x 32m [672 sq.m]) in the 1970’s, and has been decreasing since. The minimum frontage or width of a block is around 5 m to 9 m depending on location and type of dwelling.

Minimum block size can be as low as 300 sq.m, with lower permitted if there are multiple dwellings on the site. For example 200 sq.m to 225 sq.m in some development plans. Others set 600 sq.m for first 5 dwellings (approx. 120 sq.m/dwelling), with 115 sq.m for each additional dwelling. But depending on the council areas these minimums may need to be much larger. For example in Yorke Peninsula council area, minimum site area is 1200 sq.m for a site not connected to community waste water management system (eg. uses septic tank), and 450 sq.m if connected to such system.

The smallest area I have found thus far is 81 sq.m in the Yorke Peninsula development plan for caravan and residential parks. This is equivalent to a site 9m x 9m, which can be divided into three strips, 3m wide: one used for caravan and two used for vehicles.

This I thought was good, as my idealistic meanderings, assuming maximum world population of 10 billion, with maximum city population of 10 million, and only 2/3rds of the area used for residential of 100 km diameter city, resulted in area of 16m x 16m per person. When I did such, I notionally had in mind a maximum population density of 4000 persons/sq.km. This population destiny I calculated from population data in my 1976 world atlas: where maximum densities were for Singapore and Hong Kong. From memory there was a higher density but I took that as an anomaly, some small island and not representative of urban population. More recently I have read articles indicating urban population densities reaching 100,000 persons/sq.km. I never considered the lifestyle producing the densities in Hong Kong and Singapore to be desirable to inflict on the population of the world. The higher densities seem even less desirable, though 256 sq.m per person seems reasonable. Basically want to avoid: human drones in concrete beehives, assimilated to the Borg and wired to the matrix. Space, circulation and privacy are important.

However, in 1 sq.km, can fit more than 5000 dwellings around a 500 m x 500 m central hub. Dwellings suitable for 1 person, are also suitable for 2 persons and a baby. With addition of second storey, the dwellings would be suitable for 2 adults and 2 children, increasing population from a possible 5000 persons to 20,000 persons. With 10 storey dwellings would increase to 100,000 people. The original buildings are single storey dwellings 25 sq.m, on 9m x 9m blocks of land, with 9m wide roads. To boost the population, by constructing multi-storey buildings, the smaller buildings would need to merge to have a larger footprint.

This was all a nice idea until a few weeks back, became aware of a South Australian ministers specification for caravan and residential parks: SA76A Fire Safety Requirements in Caravan and Residential Parks (December 2007). This code basically adds additional spacing and circulation requirements. It doesn’t seem to make much reference to the NCC/BCA, as its basic requirement is 3m separation between buildings/caravans, which if there is a site boundary is equivalent to 1.5m clearance from the boundary. Which then begs the question why the greater clearance requirements than the NCC/BCA?

As far as I know the NCC/BCA requirements are not based on fuel load nor intensity of the heat (Note 1). Houses can be built from similar materials to caravans: timber frame, plywood, and various polymer insulation, therefore the materials and the fire risk posed shouldn’t change the separation distances.

There are also separation distances between united sites of 4m, and separation between the caravans of 6m on the adjacent united sites, with an expectation caravans are set back 1m from boundaries. Looking at the sketches provided in the specification, and noting that the Australian Design Rules (ADR) for vehicles sets an envelope of 2.5m wide by 4.3m high, it looks like corridors adequate for vehicles are being provided all around each caravan. Though the sketches show trees scattered along the corridors.

If the separation distances are not met then there are requirements to design based on the 90 m reach of a hose attached to a fire hydrant. A block of sites serviced by one hydrant therefore has to be less than 90 m long, Assuming sites are 9m x 9m, and have them back to back between access roads, then lose 9m from centrally located hydrant, and another 9m to work on the site: so maximum length of a block is 90-18=72m, and maximum sites in length of a block 72/9=8, for a total of 16 sites in a cluster of united sites.

By defining separation distances relative to caravans rather than boundaries, the location of each arriving caravan is dependent on the current state of the adjacent sites at the time of arrival. For example if the vans on existing sites are 600 mm from site boundaries, the new arrival needs to be 2400 mm from its site boundaries. With a site 9m wide, which can be divided into 3 strips 3m wide, the caravan needs placing in the middle of the site, leaving a 3m strip on one side for the towing vehicle, and another strip on the other side of the caravan as open space.

As for the 5m x 5m dwelling, it has a 2m boundary clearance when placed in the middle of the site, and therefore 4m clearance from dwellings on adjacent sites. However this only allows for parking of a narrow vehicle. To increase to a 3m clearance on one side and 1m on the other side. Then as long as the buildings alternate sides, a minimum 3m clearance between buildings will be achieved.

Assuming towing vehicle and caravan have a maximum length of 6m, then on a 9m site, there will be 1.5m boundary clearance, and thus 3m clearance between dwellings on adjacent sites. For longer combinations, longer sites would be needed, however if vehicle remains hooked up, the width of the site can be reduced. Assuming minimum 3m width for vehicle and considering clearances only, then minimum site width is 6m, and for area of 81 sq.m, the length would extend to 13.5m. Or if take maximum vehicle length somewhere around 19m to 25m (from memory), add 3m to this, get site lengths of 22m to 28m, with areas of 22×6=132 sq.m and 28×6=168 sq.m.

Though given elsewhere in development plans residential blocks have minimum width between 5m and 9m, an allowance for 9m wide sites should be considered which would provide more open space around the caravan. So site area becomes 28×9=252 sq.m.

Now for increasing population density of residential areas, by subdividing the 1/4 acre blocks and 1/6th acre blocks. These blocks are approximately 32m long, and 21m to 32m wide. Thus get 21/9=2.33, and 32/9=3.56 strip blocks to each existing, or 21/5=4.20 and 32/5=6.4. So somewhere between 2 and 6 times the population in the existing area without need to use multi-storey buildings or elevators. Alternatively 672/81=8.3, and 1024/81=12.6 new sites from existing blocks: ignoring open space requirements and access roads. Though increasing population poses problems for existing infrastructure: especially the capacity of roads, pipes, along with power and data lines.

The two primary issues concerned with here are:

  1. Affordable housing
  2. Mobility

The mobility aspect means the demand on the infrastructure is not permanent. Though the peak demand could be anything from a quarter of a year to 25 years. Whilst expect permanent occupation to last for 1000 years or more. Our modern industrial cities are from 25 to 250 years old, though some are built on sites occupied for over 2000 years.

Now my contention is that urban sprawl is a consequence of multi-story commercial buildings, and large industrial facilities, not the use of the car. These large buildings both require a large workforce and a large market population. The land adjacent to the central business district (CBD) is too expensive for housing and so residential areas are forced away from the CBD. This is compounded by laws concerning noise and other disturbing activity, giving rise to the sleepy dormitory suburbs. Instead of building independent towns, we have built sleeping houses dependent on large cities.

To reduce urban sprawl, need to create walkable local hubs rather than having dependence on large city centres. Whilst council development plans need to restrict the size of facilities and their dependent populations. The planning approval process needs to be a lot more rigorous with respect to long term impact: and not just look at short term financial gains. Building a factory is not necessarily good for an area just because it creates employment and brings people into the area: the factory has to be the right size.

Here in Maitland (SA) the district has a population around 1000 people, it is contended to be central and an ideal place to stay whilst visiting the rest of the Yorke Peninsula. However it has few places to actually stay, and the services in the town have apparently significantly diminished over the last 30 years or so. There is a block of land which was going to be developed as a caravan park or residential park. Based on the 9m x 9m blocks, I can squeeze around 483 sites onto the land. Assuming 1 to 4 people per site that is a population of 483 to 1932 people, a potential to exceed the resident population for at least a season (eg. summer). Such population increase however would put a large increase in load on the common effluent disposal system (CEDS), whilst on-site septic tanks and drainage would significantly reduce the number of available sites and the population which can stay.

Concept Plan Crowded Caravan/Residential Park
(NB: This is not an actual proposal. It was drawn for this article only)

As the plan above shows, it would be a relatively crowded park, and reliant on entertainment and recreation outside the park (NB: this is not a proposed concept I just drew it for this article). Traffic flow on access roads would also be a problem if all vehicles leave and arrive at roughly the same time. The existing road is unsealed and would need to be sealed, to avoid kicking up dust.

Around the region towns have populations from 100 people to 1000 people, none of which seem large enough to support local business in the long term. The increasing digital age, and homeworkers however removes the need to travel to distant offices and factories. So local populations could be increased to support local bricks and mortar businesses. The permanent population increase doesn’t have to work in the bricks and mortar businesses, they can work digitally from home. So houses have to be suitable for such.

The typical development plan restricts home business to an area 30 sq.m, which can be provided by a space 5m x 6m. In a commercial building an individual office minimum dimensions of 2.4×4.8=11.52sq.m, though a minimum width from 2.7 to 3m is preferable. A shipping container has dimensions around 2.43m wide by 6.09m long, to give an area of 14.7sq.m. Whilst a common 16ft caravan has dimensions of around 2.36m x 4.875m=11.5sq.m. Thus a single office space can be moved in and out, depending on land usage.

Also to be noted is that some 16ft caravans can provide kitchen, bathroom and can sleep 2 people, possibly 4 people with upper level bunks. Though another option is to provide kitchen, laundry and bathroom in a permanent annex which the caravan connects up to on arrival to the park.

The 5m x 5m dwelling also considered was based on a reference which set minimum single bedsit area to 25sq.m. Such plans typically divide the 5m x 5m area into two strips 2.5m wide. One strip contains the laundry, bathroom and kitchen, whilst the other strip contains, dining, living and sleep areas. Such building could thus be provided as two transportable modules. Such building is for the most part suitable to 2 people not just one person. Though if consider need more space for two people, then only need to increase the total provision by one strip module, to make the building 7.5 x 5=37.5sq.m. If then allow for two children add another strip module to provide 2 additional bedrooms, to give 10×5=50sq.m. If constructed as modular then the extra bedroom module can be shipped in and out as needed by various occupants. A module the size of a shipping container can provide an office/study area and a bedroom. So if each person has one module each, then two additional modules for shared facilities,then need total of 6 modules to give 6×2.43=14.58m long building by 6m wide, depending on how the modules are arranged. For example 3 modules give 3*2.43=7.29m which can provide the width, then remaining 3 stacked on to each end, so 6m+7.29m=13.29m long. So set site width around 2+7+3=12m, and length 2+15+2=19m, whilst ignoring open space requirements. This would set area of site at 12×19=228sq.m. Given that 6 modules gives an area of 6×14.7=88.2sq.m and a 16ft caravan (11.5sq.m) has been identified as capable of sleeping 4, such dimensions are more luxury than essential. Will stick with dwelling 5m x 5m or 6m x 6m maximum, and allowing 3m boundary clearance all around gives a site 12m x 12m. Whilst a double site would provide a site 24m long. This should be acceptable as expect all vehicles to be much less than 19m.

Going back to the idealistic concepts, a block 16m x 16m was for one person, with expectation a block for 2 people is 16m x 32m, a block for four people would be 32m x 32m. A block for odd number of people not catered for unless permit L-shaped blocks or adjust the length between roads to suit. Since a typical block between roads is around 64m, a strip 16m x 64m would provide for 4 people, or the strip can be divided into two back to back sites. The two sites could cater for 2 people each, or one can cater for one person whilst the other caters for 3 people. Similarly a strip 48m long, could cater for one 3 person site, or two back to back sites, for one two people and the other for one person. My problem with my original concept is that the 16m x 16m can provide for a house 12m x 12m which divided into rooms 3m x 3m has 16 possible rooms. The main rooms required are:

  1. Kitchen
  2. Bathroom
  3. Laundry
  4. Dining
  5. Lounge
  6. Bedroom

Thus the dwelling provides for 11 possible bedrooms, potentially increasing the population by 11 times the original plan. Though if allow for garage and remove a 3m strip, then have 3×4=12 rooms and only 7 potential bedrooms, and is still significant population increase over the one original person for each site.

So given that 5m x 5m is adequate space for one person, and still a 16ft caravan is adequate, don’t want to be increasing the block of land above 9m x 9m. Sure there are open space requirements but that can be shared and common. Really looking to reduce the block size not make it bigger: with blocks combined to cater for more people. The population doesn’t need family homes to the extent it previously did, there is a large percentage of 3 bedroom houses occupied by one person, and average household occupancy across all households is less than 3 persons.

So 1 to 2 person dwellings which are digitally connected and have access to shared/cooperative work space would be the direction to go. Also with access to shared/public gardens, parks, recreation and entertainment facilities. Block sizes have been decreasing and houses have been increasing in size, with domestic gardens disappearing. At the same time household assembly space has been increasing as public space disappears.

Much of the property investment has been following get rich quick schemes, build big expensive houses for the few people with high incomes. Rental property provides little benefit, as the landlords don’t own either the land or the buildings, have a mortgage. The landlords expect the tenants to pay off the mortgage and provide them with a profit. It thus costs the tenants more than if they took out their own mortgage assuming they could get one.

Thus have a problem as the existing built houses are not affordable, renting is not affordable, and new houses are potentially too far from work places and equally not affordable. The retired are moving to rural and coastal towns where houses are more affordable, but there are a lack of services in such places. A lack of services should provide job opportunities but it isn’t and thus are a lack of job opportunities and the young leave for the big cities. Similarly essential services such as provision of doctors poses a problem as cannot get the doctors to live in such places.

Possible actions in the rural and coastal towns:

  1. Reduce travel time between the locations and major cities. (eg. high speed rail, airports, seaports.)
  2. Provide still lower cost housing by reducing block size. (eg. remove the 1200sq.m by connecting more properties to CEDS)
  3. Improve digital connectivity
  4. Provide recreation areas and public space
  5. Provide public transport
  6. Provide public footpaths or walking tracks between towns
  7. Provide bicycle paths between towns
  8. Provide car parking hubs in the towns
  9. Increase goods and services available
  10. Expand educational opportunities
  11. Increase health care services

The above aimed at increasing the population and decreasing dependence on having a drivers license. With increased population bricks and mortar stores are more sustainable, and more services are possible. Activities beyond sport and rural arts and crafts become more viable. Staying becomes more attractive to those born there, those who work there can retire there, and other retired can move in, as can workers move in.

As indicated above can fit about 5000 dwellings around in 500m x 500m hub, within a 1km square. A 1000 people doesn’t seem large enough to sustain local business, or at least if not providing the right services. Most of the towns have less than 1000 people, typically around 100 to 500 people, and have little to no services. I get the impression that need around 5000 people within 5km walking distance for business to survive. Most towns are about 25km apart, though towns with commercial hubs are about 50km apart. At 100km/h that puts shops around 30 minutes away. People in suburbs seldom have to travel that far for their groceries, supermarkets in some areas are at about 1km centres, and people travel there by car at around 50km/h.

Now Tea Tree Gully has a population of 97,734 persons and population density of 1026 persons/sq.km, suggesting that around 1000 people is required for a supermarket. Suburbs around Adelaide with shopping precincts seem to have populations between 5,000 and 12,000 people. Taking Roxby Downs as an example a near full range of services requires a population around 5000.

So it would seem the issue of getting doctors into rural towns is an issue of boosting local populations to 5000 so that can provide a greater range of support services to the population. Such town potentially also better able to reach 50km to 100km radially to remote surrounding regions. Noting Kadina local population of 4587, Moonta 632, Wallaroo 4010, compared to Port Augusta 14,214 and Port Pirie 14,247. In short having 11,056 people scattered over 5,834 sq.km, is potentially better served by mobile services than anchoring them into one location. Alternatively boost services in towns by boosting the local population of the service towns.

If have mobile services then need land developed for such purpose. The circus and fair cannot come to town if there is no suitable land. A central hub, precinct or high street is also important to know where to go looking. Businesses scattered all over the place and tracked down by phone is neither helpful to the community nor the businesses themselves: presence on the ground is far more valuable.

Small Town with Community Hub, with 5256 dwellings
Two Adjacent Sites: One With Dwelling Building the Other with Caravan
(NB: Doesn’t comply with minimum separation distance requirements)
Back to Back Sites (9m x 9m) clearances greater than required. It is expected that the vehicle is only hooked up to the caravan when arriving and departing, and that the vehicle intrudes into the road during such parking and departure process.
(NB: A 1.5m square grid is shown)
Back to Back Sites (9m x 9m) with 5m x 5m dwellings
(NB: 1.5m square grid shown)

Just about any existing site can be divided into two or more small dwelling sites.

Sixth of An Acre Block with Four Bedroom House
Sixth of an Acre Block with Varying Numbers of 5m x 5m Dwellings
In first instance 15 dwellings provided with footpath circulation only.
Sixth Acre Blocks with 5m x 5m Dwellings and Varying Amounts of Parking
Sixth Acre Blocks With 16ft Caravans With two Cars per Van
(NB: Household Occupancy less than 3, and average vehicle ownership 2 vehicles per household)
Sixth of Acre Block Two Dwellings
(NB: This is closer to what local development plans are likely to allow.)
More Options for Sixth of Acre Block Including Long Strip Blocks for Semi Trailer and Prime Movers.
Set Out for Shipping Container Providing Bedroom And Study/Office
(NB: Based on Internal Dimensions of Lined Container)
Back to Back Block Layout With Roads and Council Strip (Sixth of An Acre Blocks)

Notes:

  1. My primary use of the NCC/BCA is section B (structure), and then I have little interest has it is mostly a list of Australian Standards. Just interest in one part taken from AS1170 and put in the BCA. Most of the buildings I am involved with are Type C construction, warehouses, factories, farm buildings, and residential sheds, and garages, carports. As long as the commercial/industrial buildings are 3m from boundary no fire rated construction is required, and that is what is usually chosen by the developers. Residential sheds typically have boundary set backs set by development plans, and these typically exceed minimum boundary separation required for fire resistance. So I have little need to read Section C (Fire Resistance) or any of the BCA on a regular basis, however I was just (9/6/2019) looking for the clause specifying the 3m clearance in the recently released NCC/BCA:2019 and discovered tables CV1 and CV2 which are concerned with heat flux and separation distance. I have vague recollection the tables have been there for a while, the table names seem familiar, I just have little use for that part of the code and forgot. So a united site, is similar to buildings on same allotment, and table CV2, whilst separation between united sites is similar to buildings on adjoining allotments, table CV1. Though all caravan sites could be considered to relate to buildings on same allotment or adjoining allotment; so what ever the choice is only use one of the tables for everything. Though CV2 is basically doubling the distances of CV1, which roughly expect as CV1 is boundary separation and CV2 is building separation. So 6m between buildings, is similar to 3m from boundary, and 3m between buildings is similar to 1.5m from boundaries. So roughly from table CV2 heat flux generated if caravan on fire is 20 kW/m² and neighbouring caravans are expected to resist this to prevent the spread of fire. The closest classification of the caravans as buildings is BCA class 1, which requires reference to BCA/2, whilst above was based on BCA/1. In BCA/2 heat flux is given in Tables V2.3.1.3 and V2.3.1.4 page 56, if a wall with a fire resistance level (FRL) i srequired due to not meeting separation distances then it seems the FRL needs to be 60/60/60 (page 259). Besides masonry not less than 90mm thick, various light weight forms of construction can be used. These light weight methods employ multiple layers of fire rated plaster board: as to whether these can be suitably adapted into a weather resistant fence is another matter. Also if constructing a boundary fence, then will have to mirror the plaster board to both sides of the main frame. Boral OutRwall and Fireclad are examples.

Revisions:

  1. [25/05/2019] : Original Draft
  2. [26/05/2019] : Extended
  3. [09/06/2019] : Added Notes