Level #1	Level #2	Level #3	Factor Description	Relation to Constructability Concepts	Reference
Level #1	Level #2	Level #3	Factor Description	Relation to Constructability Concepts	Reference
Design Attributes	Standardization	Prefabrication	Precast Concrete, Prefabricated utility products, etc.…	A repeated grid layout will leads to faster construction sequences and reduce production waste.	[25] , [26]
		Grid Layout	Horizontal/Vertical/Radial Grid dimensions		[25] , [26]
		Standard Dimensions	Dimensions for door, windows, partitions, tiles, etc.…	Dimension of building elements should reflect material sizes and should be designed to minimize labour requirements and wastage of material by special cutting.	[27]
		Resources’ Availability	Availability of materials or special equipments.	Designers should use widely available materials that can be economically feasible.	[25]
		Labour’s Skills	Availability of special labour skills	Designs should improve constructability by designing for economical use of available skilled workers.	[27] , [28]
Construction Attributes	Installation	Construction Sequence	Sequence of installation of components.	Appreciating the sequence of operations and trade interrelationships on site can enhance constructability of design.	[27]
		Time under Ground	Construction time under ground level.	Reducing the construction time below ground level can improve constructability.	[28] [29]
		Building Envelope	Construction of the whole building envelope.	Designers should facilitate the enclosure of building at the earliest possible stage to exclude hind rage and damage because of bad weather.	[28] [29]
		Weather Effect	Effect of climate conditions on construction work.		[28] [29]
		Safety	Effect of construction sequence of workers’ safety.	The design should be arranged so as to facilitate safe working in foundations and earthworks.	[21]
	Accessibility	Material Access	Space for material storage and transportation on site.	The efficient location and distribution of temporary works and storage areas are necessary for good buildability.	[25] [28]
		Personnel Access	Accessibility of equipments and tools for and from different site locations.		[25] [28]
		Equipment Access	Accessibility of personnel for different site locations.	Designers must consider the contractor problems of access to and around construction sites.	[25]
Site Impacts	Adjacent Structures	To Adjacent Foundation	Effect of current construction to adjacent constructions.	Site conditions should be thoroughly investigated to avoid subsequent delays thoroughly after construction has commenced.	[29]
Site Impacts	Adjacent Structures	To Infrastructure	Effect of current construction to adjacent or nearby infrastructure constructions.		[29]