In many developed countries the recent increase in tourist and farm buildings in the countryside has seriously jeopardized the attractiveness of natural and traditional views; such is the case of inland Spain. Visual and aesthetic aspects of any object are defined by their colour, form, line, texture, scale and spatial character. This paper investigates lines and forms and tries to develop design criteria that could offer a high probability of achieving a building integration class as good or very good. The main aim of this research is to develop guidelines for future municipal planning laws, which could help professional designers and town council planners to select lines and forms that harmonize architectural design and environmental location. The proposed approach studies the relationship between buildings and their background. A method is developed to assess these visual relationships among building characteristics of lines and forms and the landscape ones. Also, this research includes public survey methods to assess building integration preferences and a summary table for systematic application of the suggested methodological process. Relevant correlations have been obtained, for example, whereas a type of relationship (visual continuity) provides a probability of 72% of achieving an integration class as good or very good other one (poorly compatible contrast) provides 0%. These relationships between different types of visual characteristics are satisfactory for the study of integration quality. Objective design guidelines are obtained and it is possible to make an evaluation of the different alternatives available and to select the most suitable according to the type of integration sought.

The perception of apparent sizes of buildings in a rural environment depends on the height ratio between the building and its surrounding vegetation, and it is this parameter which is currently used to assess the built landscapes. The impact of a contrasting height is less strong if the building does not exceed the horizon line. For buildings overshooting the skyline, the building’s level of sharpness and number of lines in contrast to the sky determines the impact of the scales, and vegetation in the background helps to reduce impact. The specific objectives of the present study were: (1) finding height–ratio thresholds between building and background vegetation, which may improve the integration of rural buildings in sky-sensitive locations, and; (2) comparing the results in two rural contexts with very different climatic conditions: Spain and Sweden. A survey of eighteen scenarios (nine Spanish and nine Swedish), all digitally modified with different relative height ratios between vegetation and buildings, was performed. The survey was evaluated by the public from both countries. Regardless of the country of origin, integration of the building was good or very good when the vegetation in background did not exceed one half of the height of the construction. These results may be translated to technical criteria for planning assessment.