建蔽率與容積率管制誘發開發商建築違建現象之探討 ─台南市新建透天住宅之實證分析Influence of Building Coverage Ratio and Floor Area Ratio on Illegal Constructions of Developers: An Empirical Study of Newly-Built Townhouses in Tainan City
在1997年台灣全面實施容積管制後，違章建築比例逐漸增加。以台南市為例，至2004年經查 報之違章建築比例甚至超過40％。在諸多違章建築行為當中，法定空地違建、陽台違建及屋頂平台違建等三種行為係直接增加了建築物內部之樓地板面積，本研究稱之為「容積誘發之違建行為」， 諸多開發商將此類之違建行為歸究於都市計畫之建蔽率與容積率管制。本研究以台南市開發商新建透天住宅產品為研析樣本，將開發商違建行為之影響因素區分為土地與建築物等二項因素，針對因容積管制而誘發之三種違建行為進行分析。藉由二項羅吉特模型對各類型之違建行為，分別進行是否違建之模型建構，並以次序羅吉特模型分析違建現象之嚴重程度。實證結果發現法定建蔽率與容積率對法定空地違建有顯著負面影響效果；意即法定建蔽率與容積率越高者則法定空地違建之機率越低，土地單價則有顯著正面影響。而在陽台違建與屋頂平台違建部分，則發現土地使用條件的影響效果並不明顯，只有土地單價對屋頂平台違建有正面影響效果。在違建嚴重程度部分，本研究發現，法定建蔽率與容積率有顯著負面影響效果，而土地單價則有正面影響。
Since floor area ratio(FAR) controls were first implemented in 1997, the proportion of illegal constructions in Taiwan has been increasing. In Tainan City, for example, structures erected without building permission exceeded 40 percent of all structures until 2004. Construction on statutory vacant land and the addition of balconies or rooftop structures without building permits directly and illegally increases the overall floor area of buildings. This study refers to these as “FAR-induced” illegal constructions. Many developers have ascribed the growth in these constructions as being due to the building coverage ratio(BCR) and FAR controls imposed by urban planning. This study adopts newly-developed townhouses in Tainan City as the study sample. The factors influencing illegal constructions by developers were divided into land factors and building factors, and the analysis was conducted on the “FAR-induced” illegal constructions. Using a binomial logit model, we constructed a model to reflect illegal constructions. With an ordered logit model, we investigated the severity of this illegal phenomenon. The empirical results of this study revealed that BCR and FAR have a significant negative impact on construction on statutory vacant land. This indicates that a higher BCR and FAR would lower the likelihood of developers building on statutory vacant land. In addition, the unit land price was found to have a significant positive impact on illegal constructions. In regard to the addition of balconies or rooftop structures without building permits, the impact of land use conditions was not significant, while the unit land price had a positive impact on illegal additions of rooftop structures. In terms of the severity of illegal constructions, this study concludes that the statutory BCR and FAR have a significant negative impact and that the unit land price has a positive impact.
Key words: housing, building coverage ratio, floor area ratio, illegal construction, developer, logit model