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plumbing system design
22 January 2021
Hitesh Panchal

Considering External Services for Building Design

A long time ago, somewhere in the Third World, a large, luxury-fitted, modern apartment complex was built in record time and apartment units were sold, only for residents to discover that their beautiful chrome-plated bathroom fixtures and kitchen taps were stone dry; the entire complex was devoid of any water connections. Granted, this is not a common occurrence, but it does illustrate the importance and necessity of reliable and well-designed external services in building design, which includes more than water connections. In fact, in most cases, it is a starting point in the construction process. It is imperative to source high-quality building engineering design services from reputed building services design consultants to ensure that external services are efficient and dependable.

What do we mean by external services in building design?

External services is a term used to describe material and routes of all building services outside the main building footprint and within the site perimeter, including water supply, wastewater piping, surface water drains, cables and pipes for utility supplies (internet connection, gas, electricity, telecommunications, etc.). It involves bringing all these services from the main lines, outside the compound and in a public area, to the building under construction.

Typically, external services can include:

  • Water mains supply
  • Irrigation systems
  • Electricity mains supply and distribution
  • External security systems
  • Site/street lighting systems
  • External transformation devices (wind turbines, solar panels, satellite dishes)
  • Gas mains supply
  • Fuel storage and piped distribution systems
  • Local/district heating installations
  • Telecommunications and other communication system connections

When speaking of electricity and plumbing, external services include the lines taken from the site perimeter to the building, the cabling, landscape lighting, etc. Electricity is taken to a central location on the site or in the building and then branches out. Plumbing involves water supply and wastewater connected from the main water/sewage lines outside to inside the compound and inside the structure. Mechanical services include chillers (either air or water-based), which are installed in the basement, and chiller pipes run vertically to the floors above. However, in large projects, sometimes a mechanical plant room is a separate building, which falls into the realm of external services. Routes and layouts for fire design devices outside a building are also part of external services.

There are other facets to external services which are not so obvious, such as:

  • Internet cables
  • Disconnecting chambers
  • Conduits to different levels for outside swimming pools
  • Requirements for manhole covers, both for water and electricity
  • External water supply connection line and ferrules (metal bands to strengthen or form a joint)

Each of these facets must be carefully considered by building services design consultants. Other key considerations include:

  • Careful routing of pipelines to prevent corrosion
  • Pipelines should be laid over a sand bed that is at least 150mm thick.
  • Pipes should be painted before laying them out to help prevent damage.
  • Wastewater and rainwater pipes should be easy to access for repair or replacement.
  • Strong, durable material and careful layout design is needed for the external soil line (drainpipes that carry off sewage waste).
  • Ground reservoir and the house top reservoirs must be checked for water tightness and their capacity.
  • There must be adequate arrangements for continuous water supply during peak hours. Connecting valves must be checked to see that they function properly.
  • Internal pathways and surface drains must be carefully designed.

So, who are the main protagonists in external services design and what do they do?

  • First and foremost, building services design consultants must consider all external services required for the site, and they must be on the same page as the architect. This will involve frequent and detailed consultations.
  • Site developers must obtain precise site information, conduct surveys to determine the capacity, extent and position of external services design.
  • Then, building services design consultants must ensure that the routing of cables, pipes and other materials are without fault and do not clash with each other.
  • There is a separate consultation for certain external services, which involve lux levels, manhole distances and manhole depths, which may differ from region to region and country to country.
  • In large homebuilding projects, there may be a need for multiple inter-connected substations.
  • Gardens and other green areas outside the building may be watered by automated irrigation systems. The decision to opt for drip irrigation systems, to precisely release water to plant roots, or micro spray systems, to deliver fine water sprays over a defined area, must be taken early on by building services design consultants.

Part of the range of external services provided is external drainage. These drainage systems will need to be connected to the main sewage lines outside the site.

There are generally 3 types of external drainage systems to be considered. They are:

Foul drainage: Above- ground sanitary pipework joins underground pipework or foul drainage or sewers, carrying wastewater from bathrooms and kitchens.

Surface water drainage: Building wastewater from rain, condensation and melted snow/ice are guided through roof guttering and rainwater pipes, which connect to underground pipework or surface water drains and surface water sewers.

Sustainable urban drainage systems: This is an alternative system to traditional drainage systems, such as filter strips and drains, swales, rainwater harvesting tanks, permeable surfaces, basins, ponds, underground storage, wetlands, etc.


External services design is an extensive exercise and requires both skills and the relevant software tools. With the help of BIM (Building Information Modelling) technology and the BIM-enabled software, precise designs can be generated. Software that is typically used for external services design can be as follows:

  • PowerCad for electrical design and calculations
  • AGi32, DIAlux for lighting design
  • Revit MEP for MEP modelling
  • The External Services framework of Revit software helps customise MEP (mechanical, electrical and plumbing) calculations, access externally stored data and replace built-in export/import filters and perform other tasks with a coding approach to help calculate MEP friction.

So, when in need of reliable building engineering design services, experienced building services design consultants will deliver high-quality BIM MEP services and building services coordination within a reasonable budget. These design services providers will have the expertise to provide precise building design documentation, drafting and modelling for external services.

XS CAD has valuable experience providing MEP Design services, BIM MEP services, engineering design services, building services coordination and M&E design engineering support for global firms. Our range of mechanical engineering design services for MEP design consultants include MEP drafting, MEP BIM modelling and MEP coordination.