The purpose of this research was to study level of the preliminary cost calculate for a large building in Roi Et province and to study the factors that affected on initial cost reduction of large building constructions in Roi Et province. The sample group used in this research were devisers supervisors project managers and construction contractors in Roi Et province. There were 5 projects with a total of 145 people. The instruments used in the research were a 5 level rating estimation questionnaire. Data were analyzed by using frequency percentage mean standard deviation and the hypothesis tested by using Multiple Linear Regression with (Enter Regression). The result of the research shows that An analysis of opinion on principal control of large building constructions in Roi Et province. It was found that the practice level was at the highest level. Which is arranged in order from the highest average to the lowest namely machinery cost material cost contractor cost operating cost and labor costs respectively. and The analysis of Regression Model Development for Preliminary Calculate Cost of construction works had resulted in lowering the initial cost of large building constructions in Roi Et Province of 5 factors included structural design architectural design interior design system design and exterior design. Resulting in reducing the initial cost of large building constructions in Roi Et province with statistical significance at the level of .01 level.

The purpose of this research is to study the construction safety measure for working at height. The safety measure for working at height in this research is developed by referring to the Ministerial Regulations prescribing the standard for administration and management of occupational safety health and environment for construction work 2008. The average of safety is low in five high rise construction projects in Bangkok metropolitan. So all parties involved in contractors need to focus on safety measure for working at height.

The purpose of this research is to study the effect of safety measure to construction productivity for ceiling activity by studying a construction of buildings in Bangkok. The safety system composed of (1) stable scaffolding system (2) providing clean and not slip walkways on the scaffold (3) installation of handrails not less than 0.90 meters in height (4) installing stairs (5) providing personal protective equipment for workers (6) are responsible for scaffolding and (7) scaffolding permit document. Cost of the safety system is 23908 baht or approximately 33 baht/m2. Productivity rates for prior and after the used of safety system are 1.57 and 1.41 m2. /person/hr. respectively. The productivity declines for approximately 10.19 % the working time for ceiling could take longer for 10.45 % and labor cost could increase for 10.19 %.

The purpose of this research is to study the effect of a safety system provided for wall tile external building activity on productivity. The safety system composed of (1) stable scaffolding system (2) providing clean and not slip walkways on the scaffold (3) installation of handrails not less than 0.90 meters in height along sides of the scaffold (4) installing safety nets around outside perimeters of the scaffolding (5) indicating working area (6) installing stairs (7) providing protection for people who works below (8) providing tools and equipments for transporting material which are safe and ready for using and (9) providing personal protective equipment for workers. Cost of the safety system is 79318 baht for a wall tile area of 385 m2 or approximately 206 baht/m2. Productivity rates for prior and after the used of safety system are 1.91 and 1.85 m2/person/day respectively. The productivity declines for approximately 3 %. In addition our study found an impact of work is a height of Building the wall tile external productivity could decrease for 6 %.

The purpose of this research is to study the effect of a safety system provided for column reinforcement activity on productivity by studying a construction of buildings in Bangkok. The safety system composed of (1) stable scaffolding system (2) providing clean and not slip walkways on the scaffold (3) installation of handrails not less than 0.90 meters in height (4) installing stairs and (5) providing personal protective equipment for workers. Cost of the safety system is 40030 baht for a column reinforcement area of 40 numbers. Productivity rates for prior and after the used of safety system are 11.06 and 8.80 kg./person/hr. respectively. The productivity declines for approximately 20.43 % the working time for column reinforcement could take longer for 13.18 % and labor cost could increase for 13.32 %.