The backbone for Interior Design — building systems
Growing your knowledge of building systems and construction is key to passing the NCIDQ Exam. It helps set you apart as a professional interior designer.
Even if your focus is on interior decoration, it's likely that a good part of your work will still depend upon integration with building systems. Interior designers are part of the building design team, and need to be knowledgeable on today’s building system design and equipment.
Interior designers work closely with other design and construction professions to provide functional, sustainable, and healthy buildings. This includes all types of commercial and residential new construction and remodeling projects. They must understand the viewpoints and respect the expertise of other design professionals.
Building systems are an extensive part of all 3 NCIDQ Exams, and you'll also want to refer to the building systems and systems integration lessons within Qpractice for examples of possible conflicts between the design and the building's systems and how to prevent or resolve these.
Building Systems and Integration with Construction
Doors, windows, studs, and wallboard are combined to create assemblies. One example of an assembly is a partition wall or ceiling made up of different building components.
Building components are major construction elements but don't include finish materials. As with the human body, these are the working elements underneath the interior or exterior finish layer or “skin”.
Here are a few building components:
- Studs – 2×4 and 2×6 wood studs are typical for residential applications while metal studs set into C-channels on the ceiling and floor are common in commercial spaces. Sizes of metal studs vary, but 2-1/2″ is the most common. Spacing is typically 16″ or 24″ center-to-center.
- Gypsum wallboard – Comes in different thicknesses, sizes, fire ratings for commercial / residential applications. Residential partitions usually are made of 1/2″ wallboard and 5/8″ for commercial spaces.
- Lath and plaster
- Masonry – Stone, concrete block, glass block, etc.
- Doors and door frames – There's a lot of additional information to learn about fire-rated doors. Here's a few different door materials:
- Wood – hollow core and solid core
- Steel – a.k.a. “hollow metal” doors
There's a saying that the ceiling is the “fifth wall” of a room but is an often forgotten design element. There are several types of ceilings and each is constructed differently, so you'll need to study up on the details. Here's a peek at some different ceiling components you'll need to know:
- Gypsum wallboard – Most common in residential spaces.
- Suspended acoustic – Typical of most commercial spaces. Fibrous tiles are set into a suspended grid system.
- Lath and plaster
- Integrated – Ceiling includes integral lighting, HVAC grilles, sprinklers and partition connection points
Buildings are classified in the interest of fire safety. Along with the occupancy group classification, construction classifications limit the area and height of buildings for safety reasons. For example, preventing a fire from spreading to adjacent buildings and the safe exit of occupants.
The International Building Code (IBC) classifies buildings into five different construction type categories. Construction components included in the rating are: structural framing; interior and exterior bearing walls; floor and roof.
Each category represents a different level of fire resistance, Type I being the most resistive and Type V the least resistive.
For an interior design project that has major changes, you'll need to find out what the building's construction type is, especially if the building's occupancy classification is changing.
Fire ratings of structural components, such as structure, openings, and floor/ceiling assemblies may have to be changed. Sometimes, sprinklers will need to be added.
Depending on the local jurisdiction, interior designers may be allowed to make these changes. Otherwise, an architect will be required.
An interior designer must have a good basic knowledge of the different types of structural systems. You need to be able to read and understand an engineer's or architect's plans and know what the possibilities and limitations are based on the structural system.
Understanding what is in an interior designer's scope of work, and when an architect or structural engineer needs to be involved in the project is vital.
Common scenarios you'll likely encounter as an interior designer are whether:
- a wall is load-bearing or not
- penetrations can be made through a ceiling or floor
- fire protection needs to be repaired or replaced
- a new addition will structurally integrate with existing construction
Types of structural systems
You’ll need to know the subtypes, details and pros/cons associated with each structural system.
Be familiar with terminology and dimensions of studs, joists, headers, lintels, glue-lams, sole plate top plate, sheathing, I-joists and LVL.
- Beam-and-girder system
- Open web joist system
- Cast-in-place concrete
- Pre-cast concrete
- Concrete masonry units (CMU), otherwise known as concrete block
Different loads cause different kinds of stresses on a building. You’ll need to be familiar with what aspects of each affect the realm of the interior designer.
- Gravity loads
- Live load – movable loads, such as people, furniture, and equipment
- Dead load – non-movable loads, such as the weight of the building
- Lateral loads – loads from natural occurrences, like wind and earthquakes
- Dynamic loads – loads created from impact, such as moving/stopping elevators
Mechanical and Electrical Systems
Mechanical and plumbing systems are some of the most common types of building systems that interior designers work with.
Mechanical systems include heating/cooling, plumbing, fire protection and electrical.
Like structural systems, an interior designer isn't responsible for designing these systems but needs to be able to read and understand an engineer's plans and have a basic informed knowledge of the different system types.
Heating venting and air conditioning (HVAC)
Be aware of the different HVAC systems and the fundamental workings of each, like the heating/cooling source, how it's transported and how return air is sent back through the system.
System requirements, like spacing for ducts, mixing boxes and piping will need to be considered by the interior designer. HVAC systems often interfere with desired light fixture placement and other recessed ceiling items, such as speakers. So, coordination early on in the project is ideal.
Window treatments can affect the heating and air conditioning load in the space. Placement of grilles, registers and thermostats can affect the furniture layouts.
Different mechanical systems are listed below. You'll need to be familiar with the specifics of each:
- All-air systems
- All-water systems
- Combination / terminal reheat systems
Some HVAC-related terms you'll need to know are: plenum, chase wall, mixing box, VAV box, air diffuser.
You'll need to know how to read duct sizes on plans. Remember the first number refers to the width of the duct while the second represents its height. So, 16 x 14 means a sixteen inch by fourteen inch duct.
Many interior design projects include plumbing. Being one of the costlier items in construction, it also comes with a lot of space constraints.
An interior designer should be familiar with how to read and interpret the engineer's plumbing plans.
Some key points to remember:
Plumbing locations and slope
- Locate new plumbing fixtures as close as possible to existing plumbing lines or on a plumbing trench
- Minimum slope for a drain is 1/4 inch per foot for pipes 2-1/2 inches diameter or less, and 1/8″ for pipes 3 to 6 inches in diameter
Some plumbing terms you'll need to know include: water supply, drainage, trap, vent, soil stack, waste stack, stack vent, wet column, branch water lines, toilet carrier.
Fire protectionFire protection includes both fire containment and fire suppression. Fire protection has three goals:
- Protection of life
- Protection of property
- Restoration and use of the building after a fire
Fire containment is achieved in 2 ways:
- Compartmentalization – The aim is to contain a fire, limit its spread with the dual objective to allow occupants to escape the building and protect the unaffected parts of the building. Compartmentalization is achieved structurally through:
- Door ratings
- Floor-ceiling assemblies
- Fire-rated walls
- Fire separations
- Smoke control – More victims die of smoke inhalation than from fire.
Designers must be vigilant in not designing anything to compromise any methods of smoke control designed by the engineer. Some examples of smoke control include:
- Fire dampers and gaskets
- Automatic-closing fire doors
- Specially designed smoke exhaust systems
Fire suppression is achieved through:
- Smoke detectors, rise-in temperature and flame detection alarm systems
- Fire suppression systems including sprinklers and dry chemical systems
- Portable fire extinguishers
As a designer, you need to know the different types of devices and appropriate locations within based on code requirements.
An electrical engineer creates the final electrical plans for a project. But first, the interior designer creates a plan showing where the desired locations for the outlets, switches, and any special electrical devices. Any key dimensions, including installation height, should be detailed.
Like the other mechanic trades, it is the responsibility of the designer to have a working basic knowledge of electrical systems. Here's the low-down:
Cables (also called conductors) carry electricity from circuit breakers to its final destination. Here are common cabling types below. You'll need to know what type of cable is right for the application.
- Non-metallic sheathed cable
- Flexible metal-clad cable / armored cable
- Under-carpet wiring
Junction boxes are where connections to power are made, either through an outlet or where light fixtures are connected.
Safety precautions are required to prevent a fire or shock. You'll need to know the differences between each and where they're required:
- Ground fault circuit interrupters (GFIs)
- Arc-fault circuit interrupter (AFCI)
Telecommunications systems include telephones, computers, entrance buzzers, and public address speakers, to name a few. As a designer, you'll need to illustrate where these items are to be located, with any important dimensions noted and share this information with the electrical engineer.
Lighting is an extensive subject and can be quite technical. For the NCIDQ Exam, the key is to understand the differences and why one type of lighting may be better than another for a specific purpose.
Formal permitting begins when the interior designer gives the design package to the licensed contractor. The contractor submits documents to the local building department or authority having jurisdiction (AHJ). But the interior designer is responsible for making sure the design complies with all codes and regulations. Suggested revisions, if any, are typically the responsibility of the interior designer.
The design package can include:
- Location plan illustrating designed space in relation to the floor or building
- Floor plans/elevations/sections
- Architectural details
- Structural/mechanical/electrical construction details, prepared by consultant
- Schedules (finish, lighting, etc.)
- Means of egress of /occupancy for each space indicated
Some AHJ's may also request:
- Occupant load calculations
- Codes being used
- Fire-rated components with accompanying construction details
- Locations of exit signs, fire extinguishers
- Indication of sprinkler status
Once issued, the permit must be prominently displayed on the job site. The AHJ makes inspections during the following construction stages. The contractor is responsible for scheduling the inspections with the AHJ.
- Gypsum walls
- Final inspection for final finishes, electrical and plumbing and possibly other items
A Certificate Occupancy (CO) is issued by AHJ is upon successful final inspection. Some other terms are Letter of Occupancy, or Use and Occupancy (U and O). Alternatively, a Temporary Certificate of Occupancy (TCO) or Partial Certificate of Occupancy may be issued to allow the client to occupy the space while the rest is being completed.